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<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_idup.3.html">17.2.66. MPI_Comm_idup</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_idup_with_info.3.html">17.2.67. MPI_Comm_idup_with_info</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_join.3.html">17.2.68. MPI_Comm_join</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_rank.3.html">17.2.69. MPI_Comm_rank</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_remote_group.3.html">17.2.70. MPI_Comm_remote_group</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_remote_size.3.html">17.2.71. MPI_Comm_remote_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_set_attr.3.html">17.2.72. MPI_Comm_set_attr</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_set_errhandler.3.html">17.2.73. MPI_Comm_set_errhandler</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_set_info.3.html">17.2.74. MPI_Comm_set_info</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_set_name.3.html">17.2.75. MPI_Comm_set_name</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_size.3.html">17.2.76. MPI_Comm_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_spawn.3.html">17.2.77. MPI_Comm_spawn</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_spawn_multiple.3.html">17.2.78. MPI_Comm_spawn_multiple</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_split.3.html">17.2.79. MPI_Comm_split</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_split_type.3.html">17.2.80. MPI_Comm_split_type</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Comm_test_inter.3.html">17.2.81. MPI_Comm_test_inter</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Compare_and_swap.3.html">17.2.82. MPI_Compare_and_swap</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Dims_create.3.html">17.2.83. MPI_Dims_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Dist_graph_create.3.html">17.2.84. MPI_Dist_graph_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Dist_graph_create_adjacent.3.html">17.2.85. MPI_Dist_graph_create_adjacent</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Dist_graph_neighbors.3.html">17.2.86. MPI_Dist_graph_neighbors</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Dist_graph_neighbors_count.3.html">17.2.87. MPI_Dist_graph_neighbors_count</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Errhandler_create.3.html">17.2.88. MPI_Errhandler_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Errhandler_free.3.html">17.2.89. MPI_Errhandler_free</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Errhandler_get.3.html">17.2.90. MPI_Errhandler_get</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Errhandler_set.3.html">17.2.91. MPI_Errhandler_set</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Errors.3.html">17.2.92. MPI Errors</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Error_class.3.html">17.2.93. MPI_Error_class</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Error_string.3.html">17.2.94. MPI_Error_string</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Exscan.3.html">17.2.95. MPI_Exscan</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Exscan_init.3.html">17.2.96. MPI_Exscan_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Fetch_and_op.3.html">17.2.97. MPI_Fetch_and_op</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_c2f.3.html">17.2.98. MPI_File_c2f</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_call_errhandler.3.html">17.2.99. MPI_File_call_errhandler</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_close.3.html">17.2.100. MPI_File_close</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_create_errhandler.3.html">17.2.101. MPI_File_create_errhandler</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_delete.3.html">17.2.102. MPI_File_delete</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_f2c.3.html">17.2.103. MPI_File_f2c</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_amode.3.html">17.2.104. MPI_File_get_amode</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_atomicity.3.html">17.2.105. MPI_File_get_atomicity</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_byte_offset.3.html">17.2.106. MPI_File_get_byte_offset</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_errhandler.3.html">17.2.107. MPI_File_get_errhandler</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_group.3.html">17.2.108. MPI_File_get_group</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_info.3.html">17.2.109. MPI_File_get_info</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_position.3.html">17.2.110. MPI_File_get_position</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_position_shared.3.html">17.2.111. MPI_File_get_position_shared</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_size.3.html">17.2.112. MPI_File_get_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_type_extent.3.html">17.2.113. MPI_File_get_type_extent</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_get_view.3.html">17.2.114. MPI_File_get_view</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iread.3.html">17.2.115. MPI_File_iread</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iread_all.3.html">17.2.116. MPI_File_iread_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iread_at.3.html">17.2.117. MPI_File_iread_at</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iread_at_all.3.html">17.2.118. MPI_File_iread_at_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iread_shared.3.html">17.2.119. MPI_File_iread_shared</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iwrite.3.html">17.2.120. MPI_File_iwrite</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iwrite_all.3.html">17.2.121. MPI_File_iwrite_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iwrite_at.3.html">17.2.122. MPI_File_iwrite_at</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iwrite_at_all.3.html">17.2.123. MPI_File_iwrite_at_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_iwrite_shared.3.html">17.2.124. MPI_File_iwrite_shared</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_open.3.html">17.2.125. MPI_File_open</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_preallocate.3.html">17.2.126. MPI_File_preallocate</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read.3.html">17.2.127. MPI_File_read</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_all.3.html">17.2.128. MPI_File_read_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_all_begin.3.html">17.2.129. MPI_File_read_all_begin</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_all_end.3.html">17.2.130. MPI_File_read_all_end</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_at.3.html">17.2.131. MPI_File_read_at</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_at_all.3.html">17.2.132. MPI_File_read_at_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_at_all_begin.3.html">17.2.133. MPI_File_read_at_all_begin</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_at_all_end.3.html">17.2.134. MPI_File_read_at_all_end</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_ordered.3.html">17.2.135. MPI_File_read_ordered</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_ordered_begin.3.html">17.2.136. MPI_File_read_ordered_begin</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_ordered_end.3.html">17.2.137. MPI_File_read_ordered_end</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_read_shared.3.html">17.2.138. MPI_File_read_shared</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_seek.3.html">17.2.139. MPI_File_seek</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_seek_shared.3.html">17.2.140. MPI_File_seek_shared</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_set_atomicity.3.html">17.2.141. MPI_File_set_atomicity</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_set_errhandler.3.html">17.2.142. MPI_File_set_errhandler</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_set_info.3.html">17.2.143. MPI_File_set_info</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_set_size.3.html">17.2.144. MPI_File_set_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_set_view.3.html">17.2.145. MPI_File_set_view</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_sync.3.html">17.2.146. MPI_File_sync</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write.3.html">17.2.147. MPI_File_write</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_all.3.html">17.2.148. MPI_File_write_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_all_begin.3.html">17.2.149. MPI_File_write_all_begin</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_all_end.3.html">17.2.150. MPI_File_write_all_end</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_at.3.html">17.2.151. MPI_File_write_at</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_at_all.3.html">17.2.152. MPI_File_write_at_all</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_at_all_begin.3.html">17.2.153. MPI_File_write_at_all_begin</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_at_all_end.3.html">17.2.154. MPI_File_write_at_all_end</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_ordered.3.html">17.2.155. MPI_File_write_ordered</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_ordered_begin.3.html">17.2.156. MPI_File_write_ordered_begin</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_ordered_end.3.html">17.2.157. MPI_File_write_ordered_end</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_File_write_shared.3.html">17.2.158. MPI_File_write_shared</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Finalize.3.html">17.2.159. MPI_Finalize</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Finalized.3.html">17.2.160. MPI_Finalized</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Free_mem.3.html">17.2.161. MPI_Free_mem</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Gather.3.html">17.2.162. MPI_Gather</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Gather_init.3.html">17.2.163. MPI_Gather_init</a></li>
<li class="toctree-l3 current"><a class="current reference internal" href="#">17.2.164. MPI_Gatherv</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#syntax">17.2.164.1. SYNTAX</a></li>
<li class="toctree-l4"><a class="reference internal" href="#input-parameters">17.2.164.2. INPUT PARAMETERS</a></li>
<li class="toctree-l4"><a class="reference internal" href="#output-parameters">17.2.164.3. OUTPUT PARAMETERS</a></li>
<li class="toctree-l4"><a class="reference internal" href="#description">17.2.164.4. DESCRIPTION</a></li>
<li class="toctree-l4"><a class="reference internal" href="#use-of-in-place-option">17.2.164.5. Use Of In-Place Option</a></li>
<li class="toctree-l4"><a class="reference internal" href="#when-communicator-is-an-inter-communicator">17.2.164.6. When Communicator Is An Inter-Communicator</a></li>
<li class="toctree-l4"><a class="reference internal" href="#errors">17.2.164.7. ERRORS</a></li>
</ul>
</li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Gatherv_init.3.html">17.2.165. MPI_Gatherv_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get.3.html">17.2.166. MPI_Get</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_accumulate.3.html">17.2.167. MPI_Get_accumulate</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_address.3.html">17.2.168. MPI_Get_address</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_count.3.html">17.2.169. MPI_Get_count</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_elements.3.html">17.2.170. MPI_Get_elements</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_elements_x.3.html">17.2.171. MPI_Get_elements_x</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_library_version.3.html">17.2.172. MPI_Get_library_version</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_processor_name.3.html">17.2.173. MPI_Get_processor_name</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Get_version.3.html">17.2.174. MPI_Get_version</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Graph_create.3.html">17.2.175. MPI_Graph_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Graph_get.3.html">17.2.176. MPI_Graph_get</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Graph_map.3.html">17.2.177. MPI_Graph_map</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Graph_neighbors.3.html">17.2.178. MPI_Graph_neighbors</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Graph_neighbors_count.3.html">17.2.179. MPI_Graph_neighbors_count</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Graphdims_get.3.html">17.2.180. MPI_Graphdims_get</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Grequest_complete.3.html">17.2.181. MPI_Grequest_complete</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Grequest_start.3.html">17.2.182. MPI_Grequest_start</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_c2f.3.html">17.2.183. MPI_Group_c2f</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_compare.3.html">17.2.184. MPI_Group_compare</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_difference.3.html">17.2.185. MPI_Group_difference</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_excl.3.html">17.2.186. MPI_Group_excl</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_f2c.3.html">17.2.187. MPI_Group_f2c</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_free.3.html">17.2.188. MPI_Group_free</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_from_session_pset.3.html">17.2.189. MPI_Group_from_session_pset</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_incl.3.html">17.2.190. MPI_Group_incl</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_intersection.3.html">17.2.191. MPI_Group_intersection</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_range_excl.3.html">17.2.192. MPI_Group_range_excl</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_range_incl.3.html">17.2.193. MPI_Group_range_incl</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_rank.3.html">17.2.194. MPI_Group_rank</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_size.3.html">17.2.195. MPI_Group_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_translate_ranks.3.html">17.2.196. MPI_Group_translate_ranks</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Group_union.3.html">17.2.197. MPI_Group_union</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iallgather.3.html">17.2.198. MPI_Iallgather</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iallgatherv.3.html">17.2.199. MPI_Iallgatherv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iallreduce.3.html">17.2.200. MPI_Iallreduce</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ialltoall.3.html">17.2.201. MPI_Ialltoall</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ialltoallv.3.html">17.2.202. MPI_Ialltoallv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ialltoallw.3.html">17.2.203. MPI_Ialltoallw</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ibarrier.3.html">17.2.204. MPI_Ibarrier</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ibcast.3.html">17.2.205. MPI_Ibcast</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ibsend.3.html">17.2.206. MPI_Ibsend</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iexscan.3.html">17.2.207. MPI_Iexscan</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Igather.3.html">17.2.208. MPI_Igather</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Igatherv.3.html">17.2.209. MPI_Igatherv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Improbe.3.html">17.2.210. MPI_Improbe</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Imrecv.3.html">17.2.211. MPI_Imrecv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ineighbor_allgather.3.html">17.2.212. MPI_Ineighbor_allgather</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ineighbor_allgatherv.3.html">17.2.213. MPI_Ineighbor_allgatherv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ineighbor_alltoall.3.html">17.2.214. MPI_Ineighbor_alltoall</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ineighbor_alltoallv.3.html">17.2.215. MPI_Ineighbor_alltoallv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ineighbor_alltoallw.3.html">17.2.216. MPI_Ineighbor_alltoallw</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_c2f.3.html">17.2.217. MPI_Info_c2f</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_create.3.html">17.2.218. MPI_Info_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_create_env.3.html">17.2.219. MPI_Info_create_env</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_delete.3.html">17.2.220. MPI_Info_delete</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_dup.3.html">17.2.221. MPI_Info_dup</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_env.3.html">17.2.222. MPI_Info_env</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_f2c.3.html">17.2.223. MPI_Info_f2c</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_free.3.html">17.2.224. MPI_Info_free</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_get.3.html">17.2.225. MPI_Info_get</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_get_nkeys.3.html">17.2.226. MPI_Info_get_nkeys</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_get_nthkey.3.html">17.2.227. MPI_Info_get_nthkey</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_get_string.3.html">17.2.228. MPI_Info_get_string</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_get_valuelen.3.html">17.2.229. MPI_Info_get_valuelen</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Info_set.3.html">17.2.230. MPI_Info_set</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Init.3.html">17.2.231. MPI_Init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Init_thread.3.html">17.2.232. MPI_Init_thread</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Initialized.3.html">17.2.233. MPI_Initialized</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Intercomm_create.3.html">17.2.234. MPI_Intercomm_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Intercomm_create_from_groups.3.html">17.2.235. MPI_Intercomm_create_from_groups</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Intercomm_merge.3.html">17.2.236. MPI_Intercomm_merge</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iprobe.3.html">17.2.237. MPI_Iprobe</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Irecv.3.html">17.2.238. MPI_Irecv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ireduce.3.html">17.2.239. MPI_Ireduce</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ireduce_scatter.3.html">17.2.240. MPI_Ireduce_scatter</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Ireduce_scatter_block.3.html">17.2.241. MPI_Ireduce_scatter_block</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Irsend.3.html">17.2.242. MPI_Irsend</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Is_thread_main.3.html">17.2.243. MPI_Is_thread_main</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iscan.3.html">17.2.244. MPI_Iscan</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iscatter.3.html">17.2.245. MPI_Iscatter</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Iscatterv.3.html">17.2.246. MPI_Iscatterv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Isend.3.html">17.2.247. MPI_Isend</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Isendrecv.3.html">17.2.248. MPI_Isendrecv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Isendrecv_replace.3.html">17.2.249. MPI_Isendrecv_replace</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Issend.3.html">17.2.250. MPI_Issend</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Keyval_create.3.html">17.2.251. MPI_Keyval_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Keyval_free.3.html">17.2.252. MPI_Keyval_free</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Lookup_name.3.html">17.2.253. MPI_Lookup_name</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Message_c2f.3.html">17.2.254. MPI_Message_c2f</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Message_f2c.3.html">17.2.255. MPI_Message_f2c</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Mprobe.3.html">17.2.256. MPI_Mprobe</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Mrecv.3.html">17.2.257. MPI_Mrecv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_allgather.3.html">17.2.258. MPI_Neighbor_allgather</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_allgather_init.3.html">17.2.259. MPI_Neighbor_allgather_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_allgatherv.3.html">17.2.260. MPI_Neighbor_allgatherv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_allgatherv_init.3.html">17.2.261. MPI_Neighbor_allgatherv_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_alltoall.3.html">17.2.262. MPI_Neighbor_alltoall</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_alltoall_init.3.html">17.2.263. MPI_Neighbor_alltoall_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_alltoallv.3.html">17.2.264. MPI_Neighbor_alltoallv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_alltoallv_init.3.html">17.2.265. MPI_Neighbor_alltoallv_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_alltoallw.3.html">17.2.266. MPI_Neighbor_alltoallw</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Neighbor_alltoallw_init.3.html">17.2.267. MPI_Neighbor_alltoallw_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Op_c2f.3.html">17.2.268. MPI_Op_c2f</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Op_commutative.3.html">17.2.269. MPI_Op_commutative</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Op_create.3.html">17.2.270. MPI_Op_create</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Op_f2c.3.html">17.2.271. MPI_Op_f2c</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Op_free.3.html">17.2.272. MPI_Op_free</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Open_port.3.html">17.2.273. MPI_Open_port</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pack.3.html">17.2.274. MPI_Pack</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pack_external.3.html">17.2.275. MPI_Pack_external</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pack_external_size.3.html">17.2.276. MPI_Pack_external_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pack_size.3.html">17.2.277. MPI_Pack_size</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Parrived.3.html">17.2.278. MPI_Parrived</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pcontrol.3.html">17.2.279. MPI_Pcontrol</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pready.3.html">17.2.280. MPI_Pready</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pready_list.3.html">17.2.281. MPI_Pready_list</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Pready_range.3.html">17.2.282. MPI_Pready_range</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Precv_init.3.html">17.2.283. MPI_Precv_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Probe.3.html">17.2.284. MPI_Probe</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Psend_init.3.html">17.2.285. MPI_Psend_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Publish_name.3.html">17.2.286. MPI_Publish_name</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Put.3.html">17.2.287. MPI_Put</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Query_thread.3.html">17.2.288. MPI_Query_thread</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Raccumulate.3.html">17.2.289. MPI_Raccumulate</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Recv.3.html">17.2.290. MPI_Recv</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Recv_init.3.html">17.2.291. MPI_Recv_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce.3.html">17.2.292. MPI_Reduce</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce_init.3.html">17.2.293. MPI_Reduce_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce_local.3.html">17.2.294. MPI_Reduce_local</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce_scatter.3.html">17.2.295. MPI_Reduce_scatter</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce_scatter_block.3.html">17.2.296. MPI_Reduce_scatter_block</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce_scatter_block_init.3.html">17.2.297. MPI_Reduce_scatter_block_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Reduce_scatter_init.3.html">17.2.298. MPI_Reduce_scatter_init</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Register_datarep.3.html">17.2.299. MPI_Register_datarep</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Request_c2f.3.html">17.2.300. MPI_Request_c2f</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Request_f2c.3.html">17.2.301. MPI_Request_f2c</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Request_free.3.html">17.2.302. MPI_Request_free</a></li>
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<li class="toctree-l3"><a class="reference internal" href="MPI_Rget.3.html">17.2.304. MPI_Rget</a></li>
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<li class="toctree-l3"><a class="reference internal" href="MPI_Rput.3.html">17.2.306. MPI_Rput</a></li>
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<li class="toctree-l3"><a class="reference internal" href="MPI_Test.3.html">17.2.373. MPI_Test</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Test_cancelled.3.html">17.2.374. MPI_Test_cancelled</a></li>
<li class="toctree-l3"><a class="reference internal" href="MPI_Testall.3.html">17.2.375. MPI_Testall</a></li>
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</style><div class="section" id="mpi-gatherv">
<span id="id1"></span><h1><span class="section-number">17.2.164. </span>MPI_Gatherv<a class="headerlink" href="#mpi-gatherv" title="Permalink to this heading"></a></h1>
<p><a class="reference internal" href="#mpi-gatherv"><span class="std std-ref">MPI_Gatherv</span></a>, <a class="reference internal" href="MPI_Igatherv.3.html#mpi-igatherv"><span class="std std-ref">MPI_Igatherv</span></a>, <a class="reference internal" href="MPI_Gatherv_init.3.html#mpi-gatherv-init"><span class="std std-ref">MPI_Gatherv_init</span></a> - Gathers varying amounts of
data from all processes to the root process</p>
<div class="section" id="syntax">
<h2><span class="section-number">17.2.164.1. </span>SYNTAX<a class="headerlink" href="#syntax" title="Permalink to this heading"></a></h2>
<div class="section" id="c-syntax">
<h3><span class="section-number">17.2.164.1.1. </span>C Syntax<a class="headerlink" href="#c-syntax" title="Permalink to this heading"></a></h3>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf"><mpi.h></span>
<span class="kt">int</span><span class="w"> </span><span class="n">MPI_Gatherv</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">recvbuf</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">[],</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">displs</span><span class="p">[],</span><span class="w"> </span><span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">recvtype</span><span class="p">,</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">)</span>
<span class="kt">int</span><span class="w"> </span><span class="n">MPI_Igatherv</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">recvbuf</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">[],</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">displs</span><span class="p">[],</span><span class="w"> </span><span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">recvtype</span><span class="p">,</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Request</span><span class="w"> </span><span class="o">*</span><span class="n">request</span><span class="p">)</span>
<span class="kt">int</span><span class="w"> </span><span class="n">MPI_Gatherv_init</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">recvbuf</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">[],</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">displs</span><span class="p">[],</span><span class="w"> </span><span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">recvtype</span><span class="p">,</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Info</span><span class="w"> </span><span class="n">info</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_Request</span><span class="w"> </span><span class="o">*</span><span class="n">request</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="fortran-syntax">
<h3><span class="section-number">17.2.164.1.2. </span>Fortran Syntax<a class="headerlink" href="#fortran-syntax" title="Permalink to this heading"></a></h3>
<div class="highlight-fortran notranslate"><div class="highlight"><pre><span></span><span class="k">USE </span><span class="n">MPI</span>
<span class="c">! or the older form: INCLUDE 'mpif.h'</span>
<span class="n">MPI_GATHERV</span><span class="p">(</span><span class="n">SENDBUF</span><span class="p">,</span><span class="w"> </span><span class="n">SENDCOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">SENDTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">RECVBUF</span><span class="p">,</span><span class="w"> </span><span class="n">RECVCOUNTS</span><span class="p">,</span>
<span class="w"> </span><span class="n">DISPLS</span><span class="p">,</span><span class="w"> </span><span class="n">RECVTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">ROOT</span><span class="p">,</span><span class="w"> </span><span class="n">COMM</span><span class="p">,</span><span class="w"> </span><span class="n">IERROR</span><span class="p">)</span>
<span class="w"> </span><span class="o"><</span><span class="k">type</span><span class="o">></span><span class="w"> </span><span class="n">SENDBUF</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">RECVBUF</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="kt">INTEGER </span><span class="n">SENDCOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">SENDTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">RECVCOUNTS</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">DISPLS</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="kt">INTEGER </span><span class="n">RECVTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">ROOT</span><span class="p">,</span><span class="w"> </span><span class="n">COMM</span><span class="p">,</span><span class="w"> </span><span class="n">IERROR</span>
<span class="n">MPI_IGATHERV</span><span class="p">(</span><span class="n">SENDBUF</span><span class="p">,</span><span class="w"> </span><span class="n">SENDCOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">SENDTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">RECVBUF</span><span class="p">,</span><span class="w"> </span><span class="n">RECVCOUNTS</span><span class="p">,</span>
<span class="w"> </span><span class="n">DISPLS</span><span class="p">,</span><span class="w"> </span><span class="n">RECVTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">ROOT</span><span class="p">,</span><span class="w"> </span><span class="n">COMM</span><span class="p">,</span><span class="w"> </span><span class="n">REQUEST</span><span class="p">,</span><span class="w"> </span><span class="n">IERROR</span><span class="p">)</span>
<span class="w"> </span><span class="o"><</span><span class="k">type</span><span class="o">></span><span class="w"> </span><span class="n">SENDBUF</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">RECVBUF</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="kt">INTEGER </span><span class="n">SENDCOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">SENDTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">RECVCOUNTS</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">DISPLS</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="kt">INTEGER </span><span class="n">RECVTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">ROOT</span><span class="p">,</span><span class="w"> </span><span class="n">COMM</span><span class="p">,</span><span class="w"> </span><span class="n">REQUEST</span><span class="p">,</span><span class="w"> </span><span class="n">IERROR</span>
<span class="n">MPI_GATHERV_INIT</span><span class="p">(</span><span class="n">SENDBUF</span><span class="p">,</span><span class="w"> </span><span class="n">SENDCOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">SENDTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">RECVBUF</span><span class="p">,</span><span class="w"> </span><span class="n">RECVCOUNTS</span><span class="p">,</span>
<span class="w"> </span><span class="n">DISPLS</span><span class="p">,</span><span class="w"> </span><span class="n">RECVTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">ROOT</span><span class="p">,</span><span class="w"> </span><span class="n">COMM</span><span class="p">,</span><span class="w"> </span><span class="n">INFO</span><span class="p">,</span><span class="w"> </span><span class="n">REQUEST</span><span class="p">,</span><span class="w"> </span><span class="n">IERROR</span><span class="p">)</span>
<span class="w"> </span><span class="o"><</span><span class="k">type</span><span class="o">></span><span class="w"> </span><span class="n">SENDBUF</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">RECVBUF</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="kt">INTEGER </span><span class="n">SENDCOUNT</span><span class="p">,</span><span class="w"> </span><span class="n">SENDTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">RECVCOUNTS</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">DISPLS</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="kt">INTEGER </span><span class="n">RECVTYPE</span><span class="p">,</span><span class="w"> </span><span class="n">ROOT</span><span class="p">,</span><span class="w"> </span><span class="n">COMM</span><span class="p">,</span><span class="w"> </span><span class="n">INFO</span><span class="p">,</span><span class="w"> </span><span class="n">REQUEST</span><span class="p">,</span><span class="w"> </span><span class="n">IERROR</span>
</pre></div>
</div>
</div>
<div class="section" id="fortran-2008-syntax">
<h3><span class="section-number">17.2.164.1.3. </span>Fortran 2008 Syntax<a class="headerlink" href="#fortran-2008-syntax" title="Permalink to this heading"></a></h3>
<div class="highlight-fortran notranslate"><div class="highlight"><pre><span></span><span class="k">USE </span><span class="n">mpi_f08</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">recvbuf</span><span class="p">,</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span>
<span class="w"> </span><span class="n">recvtype</span><span class="p">,</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="n">ierror</span><span class="p">)</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="k">DIMENSION</span><span class="p">(..),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendbuf</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="k">DIMENSION</span><span class="p">(..)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">recvbuf</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">displs</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">root</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Datatype</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">recvtype</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Comm</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">comm</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">OPTIONAL</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">OUT</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ierror</span>
<span class="n">MPI_Igatherv</span><span class="p">(</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">recvbuf</span><span class="p">,</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span>
<span class="w"> </span><span class="n">recvtype</span><span class="p">,</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="n">request</span><span class="p">,</span><span class="w"> </span><span class="n">ierror</span><span class="p">)</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="k">DIMENSION</span><span class="p">(..),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">),</span><span class="w"> </span><span class="k">ASYNCHRONOUS</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendbuf</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="k">DIMENSION</span><span class="p">(..),</span><span class="w"> </span><span class="k">ASYNCHRONOUS</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">recvbuf</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">root</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">),</span><span class="w"> </span><span class="k">ASYNCHRONOUS</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">displs</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Datatype</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">recvtype</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Comm</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">comm</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Request</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">OUT</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">request</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">OPTIONAL</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">OUT</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ierror</span>
<span class="n">MPI_Gatherv_init</span><span class="p">(</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">recvbuf</span><span class="p">,</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span>
<span class="w"> </span><span class="n">recvtype</span><span class="p">,</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="n">info</span><span class="p">,</span><span class="w"> </span><span class="n">request</span><span class="p">,</span><span class="w"> </span><span class="n">ierror</span><span class="p">)</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="k">DIMENSION</span><span class="p">(..),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">),</span><span class="w"> </span><span class="k">ASYNCHRONOUS</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendbuf</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="k">DIMENSION</span><span class="p">(..),</span><span class="w"> </span><span class="k">ASYNCHRONOUS</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">recvbuf</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">root</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">),</span><span class="w"> </span><span class="k">ASYNCHRONOUS</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">(</span><span class="o">*</span><span class="p">),</span><span class="w"> </span><span class="n">displs</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Datatype</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">recvtype</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Comm</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">comm</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Info</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span>
<span class="w"> </span><span class="k">TYPE</span><span class="p">(</span><span class="n">MPI_Request</span><span class="p">),</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">OUT</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">request</span>
<span class="w"> </span><span class="kt">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">OPTIONAL</span><span class="p">,</span><span class="w"> </span><span class="k">INTENT</span><span class="p">(</span><span class="n">OUT</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ierror</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="input-parameters">
<h2><span class="section-number">17.2.164.2. </span>INPUT PARAMETERS<a class="headerlink" href="#input-parameters" title="Permalink to this heading"></a></h2>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">sendbuf</span></code> : Starting address of send buffer (choice).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">sendcount</span></code> : Number of elements in send buffer (integer).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">sendtype</span></code> : Datatype of send buffer elements (handle).</p></li>
<li><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">recvcounts</span></code><span class="classifier">Integer array (of length group size) containing the</span></dt><dd><p>number of elements that are received from each process (significant
only at root).</p>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">displs</span></code><span class="classifier">Integer array (of length group size). Entry i specifies the</span></dt><dd><p>displacement relative to recvbuf at which to place the incoming data
from process i (significant only at root).</p>
</dd>
</dl>
</li>
<li><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">recvtype</span></code><span class="classifier">Datatype of recv buffer elements (significant only at</span></dt><dd><p>root) (handle).</p>
</dd>
</dl>
</li>
<li><p><code class="docutils literal notranslate"><span class="pre">root</span></code> : Rank of receiving process (integer).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">comm</span></code> : Communicator (handle).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">info</span></code> : Info (handle, persistent only).</p></li>
</ul>
</div>
<div class="section" id="output-parameters">
<h2><span class="section-number">17.2.164.3. </span>OUTPUT PARAMETERS<a class="headerlink" href="#output-parameters" title="Permalink to this heading"></a></h2>
<ul class="simple">
<li><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">recvbuf</span></code><span class="classifier">Address of receive buffer (choice, significant only at</span></dt><dd><p>root).</p>
</dd>
</dl>
</li>
<li><p><code class="docutils literal notranslate"><span class="pre">request</span></code> : Request (handle, non-blocking only).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">ierror</span></code> : Fortran only: Error status (integer).</p></li>
</ul>
</div>
<div class="section" id="description">
<h2><span class="section-number">17.2.164.4. </span>DESCRIPTION<a class="headerlink" href="#description" title="Permalink to this heading"></a></h2>
<p><a class="reference internal" href="#mpi-gatherv"><span class="std std-ref">MPI_Gatherv</span></a> extends the functionality of <a class="reference internal" href="MPI_Gather.3.html#mpi-gather"><span class="std std-ref">MPI_Gather</span></a> by allowing a
varying count of data from each process, since recvcounts is now an
array. It also allows more flexibility as to where the data is placed on
the root, by providing the new argument, displs.</p>
<p>The outcome is as if each process, including the root process, sends a
message to the root,</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Send</span><span class="p">(</span><span class="n">sendbuf</span><span class="p">,</span><span class="w"> </span><span class="n">sendcount</span><span class="p">,</span><span class="w"> </span><span class="n">sendtype</span><span class="p">,</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="p">...);</span>
</pre></div>
</div>
<p>and the root executes n receives,</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Recv</span><span class="p">(</span><span class="n">recvbuf</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">disp</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">extent</span><span class="p">(</span><span class="n">recvtype</span><span class="p">),</span><span class="w"> </span><span class="n">recvcounts</span><span class="p">[</span><span class="n">i</span><span class="p">],</span>
<span class="w"> </span><span class="n">recvtype</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="p">...);</span>
</pre></div>
</div>
<p>Messages are placed in the receive buffer of the root process in rank
order, that is, the data sent from process j is placed in the jth
portion of the receive buffer recvbuf on process root. The jth portion
of recvbuf begins at offset displs[j] elements (in terms of recvtype)
into recvbuf.</p>
<p>The receive buffer is ignored for all nonroot processes.</p>
<p>The type signature implied by sendcount, sendtype on process i must be
equal to the type signature implied by recvcounts[i], recvtype at the
root. This implies that the amount of data sent must be equal to the
amount of data received, pairwise between each process and the root.
Distinct type maps between sender and receiver are still allowed, as
illustrated in Example 2, below.</p>
<p>All arguments to the function are significant on process root, while on
other processes, only arguments sendbuf, sendcount, sendtype, root, comm
are significant. The arguments root and comm must have identical values
on all processes.</p>
<p>The specification of counts, types, and displacements should not cause
any location on the root to be written more than once. Such a call is
erroneous.</p>
<p>Example 1: Now have each process send 100 ints to root, but place each
set (of 100) stride ints apart at receiving end. Use <a class="reference internal" href="#mpi-gatherv"><span class="std std-ref">MPI_Gatherv</span></a> and the
displs argument to achieve this effect. Assume stride >= 100.</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">gsize</span><span class="p">,</span><span class="w"> </span><span class="n">sendarray</span><span class="p">[</span><span class="mi">100</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">stride</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">;</span>
<span class="p">...</span>
<span class="n">MPI_Comm_size</span><span class="p">(</span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">gsize</span><span class="p">);</span>
<span class="n">rbuf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">displs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">rcounts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o"><</span><span class="n">gsize</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="p">;</span>
<span class="w"> </span><span class="n">rcounts</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sendarray</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span>
<span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
</pre></div>
</div>
<p>Note that the program is erroneous if stride < 100.</p>
<p>Example 2: Same as Example 1 on the receiving side, but send the 100
ints from the 0th column of a 100 150 int array, in C.</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">gsize</span><span class="p">,</span><span class="w"> </span><span class="n">sendarray</span><span class="p">[</span><span class="mi">100</span><span class="p">][</span><span class="mi">150</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">stride</span><span class="p">;</span>
<span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">stype</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">;</span>
<span class="p">...</span>
<span class="n">MPI_Comm_size</span><span class="p">(</span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">gsize</span><span class="p">);</span>
<span class="n">rbuf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">displs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">rcounts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o"><</span><span class="n">gsize</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="p">;</span>
<span class="w"> </span><span class="n">rcounts</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span>
<span class="p">}</span>
<span class="c1">// Create datatype for 1 column of array</span>
<span class="n">MPI_Type_vector</span><span class="p">(</span><span class="mi">100</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">150</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="p">);</span>
<span class="n">MPI_Type_commit</span><span class="p">(</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sendarray</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="w"> </span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span>
<span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
</pre></div>
</div>
<p>Example 3: Process i sends (100-i) ints from the ith column of a 100 x
150 int array, in C. It is received into a buffer with stride, as in the
previous two examples.</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">gsize</span><span class="p">,</span><span class="w"> </span><span class="n">sendarray</span><span class="p">[</span><span class="mi">100</span><span class="p">][</span><span class="mi">150</span><span class="p">],</span><span class="w"> </span><span class="o">*</span><span class="n">sptr</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">stride</span><span class="p">,</span><span class="w"> </span><span class="n">myrank</span><span class="p">;</span>
<span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">stype</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">;</span>
<span class="p">...</span>
<span class="n">MPI_Comm_size</span><span class="p">(</span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">gsize</span><span class="p">);</span>
<span class="n">MPI_Comm_rank</span><span class="p">(</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">myrank</span><span class="w"> </span><span class="p">);</span>
<span class="n">rbuf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">displs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">rcounts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o"><</span><span class="n">gsize</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="p">;</span>
<span class="w"> </span><span class="n">rcounts</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="o">-</span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="c1">// note change from previous example</span>
<span class="p">}</span>
<span class="c1">// Create datatype for the column we are sending</span>
<span class="n">MPI_Type_vector</span><span class="p">(</span><span class="mi">100</span><span class="o">-</span><span class="n">myrank</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">150</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="p">);</span>
<span class="n">MPI_Type_commit</span><span class="p">(</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// sptr is the address of start of "myrank" column</span>
<span class="n">sptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="n">sendarray</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="n">myrank</span><span class="p">];</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sptr</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="w"> </span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span>
<span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
</pre></div>
</div>
<p>Note that a different amount of data is received from each process.</p>
<p>Example 4: Same as Example 3, but done in a different way at the sending
end. We create a datatype that causes the correct striding at the
sending end so that we read a column of a C array.</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">gsize</span><span class="p">,</span><span class="w"> </span><span class="n">sendarray</span><span class="p">[</span><span class="mi">100</span><span class="p">][</span><span class="mi">150</span><span class="p">],</span><span class="w"> </span><span class="o">*</span><span class="n">sptr</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">stride</span><span class="p">,</span><span class="w"> </span><span class="n">myrank</span><span class="p">,</span><span class="w"> </span><span class="n">disp</span><span class="p">[</span><span class="mi">2</span><span class="p">],</span><span class="w"> </span><span class="n">blocklen</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span>
<span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="w"> </span><span class="n">type</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">;</span>
<span class="p">...</span>
<span class="n">MPI_Comm_size</span><span class="p">(</span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">gsize</span><span class="p">);</span>
<span class="n">MPI_Comm_rank</span><span class="p">(</span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">myrank</span><span class="w"> </span><span class="p">);</span>
<span class="n">rbuf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">alloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">displs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">rcounts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o"><</span><span class="n">gsize</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="o">*</span><span class="w"> </span><span class="n">stride</span><span class="p">;</span>
<span class="w"> </span><span class="n">rcounts</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="o">-</span><span class="n">i</span><span class="p">;</span>
<span class="p">}</span>
<span class="c1">// Create datatype for one int, with extent of entire row</span>
<span class="n">disp</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="n">disp</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">150</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">);</span>
<span class="n">type</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">;</span>
<span class="n">type</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MPI_UB</span><span class="p">;</span>
<span class="n">blocklen</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="n">blocklen</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="n">MPI_Type_struct</span><span class="p">(</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">blocklen</span><span class="p">,</span><span class="w"> </span><span class="n">disp</span><span class="p">,</span><span class="w"> </span><span class="n">type</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="n">MPI_Type_commit</span><span class="p">(</span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="n">sptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="n">sendarray</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="n">myrank</span><span class="p">];</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sptr</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="o">-</span><span class="n">myrank</span><span class="p">,</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="w"> </span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span>
<span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
</pre></div>
</div>
<p>Example 5: Same as Example 3 at sending side, but at receiving side we
make the stride between received blocks vary from block to block.</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">gsize</span><span class="p">,</span><span class="w"> </span><span class="n">sendarray</span><span class="p">[</span><span class="mi">100</span><span class="p">][</span><span class="mi">150</span><span class="p">],</span><span class="w"> </span><span class="o">*</span><span class="n">sptr</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">stride</span><span class="p">,</span><span class="w"> </span><span class="n">myrank</span><span class="p">,</span><span class="w"> </span><span class="n">bufsize</span><span class="p">;</span>
<span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">stype</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">offset</span><span class="p">;</span>
<span class="p">...</span>
<span class="n">MPI_Comm_size</span><span class="p">(</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">gsize</span><span class="p">);</span>
<span class="n">MPI_Comm_rank</span><span class="p">(</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">myrank</span><span class="w"> </span><span class="p">);</span>
<span class="n">de</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="p">...</span>
<span class="c1">// stride[i] for i = 0 to gsize-1 is set somehow</span>
<span class="c1">// set up displs and rcounts vectors first</span>
<span class="n">displs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">rcounts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">offset</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o"><</span><span class="n">gsize</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">offset</span><span class="p">;</span>
<span class="w"> </span><span class="n">offset</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">stride</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
<span class="w"> </span><span class="n">rcounts</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="o">-</span><span class="n">i</span><span class="p">;</span>
<span class="p">}</span>
<span class="c1">// the required buffer size for rbuf is now easily obtained</span>
<span class="n">bufsize</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">gsize</span><span class="mi">-1</span><span class="p">]</span><span class="o">+</span><span class="n">rcounts</span><span class="p">[</span><span class="n">gsize</span><span class="mi">-1</span><span class="p">];</span>
<span class="n">rbuf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">bufsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="c1">// Create datatype for the column we are sending</span>
<span class="n">MPI_Type_vector</span><span class="p">(</span><span class="mi">100</span><span class="o">-</span><span class="n">myrank</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">150</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="p">);</span>
<span class="n">MPI_Type_commit</span><span class="p">(</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="n">sptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="n">sendarray</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="n">myrank</span><span class="p">];</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sptr</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="w"> </span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span>
<span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
</pre></div>
</div>
<p>Example 6: Process i sends num ints from the ith column of a 100 x 150
int array, in C. The complicating factor is that the various values of
num are not known to root, so a separate gather must first be run to
find these out. The data is placed contiguously at the receiving end.</p>
<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">MPI_Comm</span><span class="w"> </span><span class="n">comm</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">gsize</span><span class="p">,</span><span class="w"> </span><span class="n">sendarray</span><span class="p">[</span><span class="mi">100</span><span class="p">][</span><span class="mi">150</span><span class="p">],</span><span class="w"> </span><span class="o">*</span><span class="n">sptr</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">stride</span><span class="p">,</span><span class="w"> </span><span class="n">myrank</span><span class="p">,</span><span class="w"> </span><span class="n">disp</span><span class="p">[</span><span class="mi">2</span><span class="p">],</span><span class="w"> </span><span class="n">blocklen</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span>
<span class="n">MPI_Datatype</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="n">types</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">num</span><span class="p">;</span>
<span class="p">...</span>
<span class="n">MPI_Comm_size</span><span class="p">(</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">gsize</span><span class="p">);</span>
<span class="n">MPI_Comm_rank</span><span class="p">(</span><span class="w"> </span><span class="n">comm</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">myrank</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// First, gather nums to root</span>
<span class="n">rcounts</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">MPI_Gather</span><span class="p">(</span><span class="w"> </span><span class="o">&</span><span class="n">num</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
<span class="c1">// root now has correct rcounts, using these we set</span>
<span class="c1">// displs[] so that data is placed contiguously (or concatenated) at receive end</span>
<span class="n">displs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="n">displs</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o"><</span><span class="n">gsize</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">displs</span><span class="p">[</span><span class="n">i</span><span class="mi">-1</span><span class="p">]</span><span class="o">+</span><span class="n">rcounts</span><span class="p">[</span><span class="n">i</span><span class="mi">-1</span><span class="p">];</span>
<span class="p">}</span>
<span class="c1">// And, create receive buffer</span>
<span class="n">rbuf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">gsize</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="p">(</span><span class="n">displs</span><span class="p">[</span><span class="n">gsize</span><span class="mi">-1</span><span class="p">]</span><span class="o">+</span><span class="n">rcounts</span><span class="p">[</span><span class="n">gsize</span><span class="mi">-1</span><span class="p">])</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">));</span>
<span class="c1">// Create datatype for one int, with extent of entire row</span>
<span class="n">disp</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="n">disp</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">150</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">);</span>
<span class="n">type</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">;</span>
<span class="n">type</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">MPI_UB</span><span class="p">;</span>
<span class="n">blocklen</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="n">blocklen</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="n">MPI_Type_struct</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">blocklen</span><span class="p">,</span><span class="w"> </span><span class="n">disp</span><span class="p">,</span><span class="w"> </span><span class="n">type</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="n">MPI_Type_commit</span><span class="p">(</span><span class="w"> </span><span class="o">&</span><span class="n">stype</span><span class="w"> </span><span class="p">);</span>
<span class="n">sptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="n">sendarray</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="n">myrank</span><span class="p">];</span>
<span class="n">MPI_Gatherv</span><span class="p">(</span><span class="n">sptr</span><span class="p">,</span><span class="w"> </span><span class="n">num</span><span class="p">,</span><span class="w"> </span><span class="n">stype</span><span class="p">,</span><span class="w"> </span><span class="n">rbuf</span><span class="p">,</span><span class="w"> </span><span class="n">rcounts</span><span class="p">,</span><span class="w"> </span><span class="n">displs</span><span class="p">,</span><span class="w"> </span><span class="n">MPI_INT</span><span class="p">,</span><span class="w"> </span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="n">comm</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="section" id="use-of-in-place-option">
<h2><span class="section-number">17.2.164.5. </span>Use Of In-Place Option<a class="headerlink" href="#use-of-in-place-option" title="Permalink to this heading"></a></h2>
<p>The in-place option operates in the same way as it does for <a class="reference internal" href="MPI_Gather.3.html#mpi-gather"><span class="std std-ref">MPI_Gather</span></a>.
When the communicator is an intracommunicator, you can perform a gather
operation in-place (the output buffer is used as the input buffer). Use
the variable MPI_IN_PLACE as the value of the root process sendbuf. In
this case, sendcount and sendtype are ignored, and the contribution of
the root process to the gathered vector is assumed to already be in the
correct place in the receive buffer.</p>
<p>Note that MPI_IN_PLACE is a special kind of value; it has the same
restrictions on its use as MPI_BOTTOM.</p>
<p>Because the in-place option converts the receive buffer into a
send-and-receive buffer, a Fortran binding that includes INTENT must
mark these as INOUT, not OUT.</p>
</div>
<div class="section" id="when-communicator-is-an-inter-communicator">
<h2><span class="section-number">17.2.164.6. </span>When Communicator Is An Inter-Communicator<a class="headerlink" href="#when-communicator-is-an-inter-communicator" title="Permalink to this heading"></a></h2>
<p>When the communicator is an inter-communicator, the root process in the
first group gathers data from all the processes in the second group. The
first group defines the root process. That process uses MPI_ROOT as the
value of its root argument. The remaining processes use <code class="docutils literal notranslate"><span class="pre">MPI_PROC_NULL</span></code> as
the value of their root argument. All processes in the second group use
the rank of that root process in the first group as the value of their
root argument. The send buffer argument of the processes in the first
group must be consistent with the receive buffer argument of the root
process in the second group.</p>
</div>
<div class="section" id="errors">
<h2><span class="section-number">17.2.164.7. </span>ERRORS<a class="headerlink" href="#errors" title="Permalink to this heading"></a></h2>
<p>Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.</p>
<p>Before the error value is returned, the current MPI error handler associated
with the communication object (e.g., communicator, window, file) is called.
If no communication object is associated with the MPI call, then the call is
considered attached to MPI_COMM_SELF and will call the associated MPI error
handler. When MPI_COMM_SELF is not initialized (i.e., before
<a class="reference internal" href="MPI_Init.3.html#mpi-init"><span class="std std-ref">MPI_Init</span></a>/<a class="reference internal" href="MPI_Init_thread.3.html#mpi-init-thread"><span class="std std-ref">MPI_Init_thread</span></a>, after <a class="reference internal" href="MPI_Finalize.3.html#mpi-finalize"><span class="std std-ref">MPI_Finalize</span></a>, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling <a class="reference internal" href="MPI_Comm_set_errhandler.3.html#mpi-comm-set-errhandler"><span class="std std-ref">MPI_Comm_set_errhandler</span></a> on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to <a class="reference internal" href="MPI_Comm_spawn.3.html#mpi-comm-spawn"><span class="std std-ref">MPI_Comm_spawn</span></a>/<a class="reference internal" href="MPI_Comm_spawn_multiple.3.html#mpi-comm-spawn-multiple"><span class="std std-ref">MPI_Comm_spawn_multiple</span></a>.
If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
handler is called for all other MPI functions.</p>
<p>Open MPI includes three predefined error handlers that can be used:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">MPI_ERRORS_ARE_FATAL</span></code>
Causes the program to abort all connected MPI processes.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">MPI_ERRORS_ABORT</span></code>
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if <a class="reference internal" href="MPI_Abort.3.html#mpi-abort"><span class="std std-ref">MPI_Abort</span></a> was called on that communicator. If
called on a window or file, acts as if <a class="reference internal" href="MPI_Abort.3.html#mpi-abort"><span class="std std-ref">MPI_Abort</span></a> was called
on a communicator containing the group of processes in the
corresponding window or file. If called on a session,
aborts only the local process.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">MPI_ERRORS_RETURN</span></code>
Returns an error code to the application.</p></li>
</ul>
<p>MPI applications can also implement their own error handlers by calling:</p>
<ul class="simple">
<li><p><a class="reference internal" href="MPI_Comm_create_errhandler.3.html#mpi-comm-create-errhandler"><span class="std std-ref">MPI_Comm_create_errhandler</span></a> then <a class="reference internal" href="MPI_Comm_set_errhandler.3.html#mpi-comm-set-errhandler"><span class="std std-ref">MPI_Comm_set_errhandler</span></a></p></li>
<li><p><a class="reference internal" href="MPI_File_create_errhandler.3.html#mpi-file-create-errhandler"><span class="std std-ref">MPI_File_create_errhandler</span></a> then <a class="reference internal" href="MPI_File_set_errhandler.3.html#mpi-file-set-errhandler"><span class="std std-ref">MPI_File_set_errhandler</span></a></p></li>
<li><p><a class="reference internal" href="MPI_Session_create_errhandler.3.html#mpi-session-create-errhandler"><span class="std std-ref">MPI_Session_create_errhandler</span></a> then <a class="reference internal" href="MPI_Session_set_errhandler.3.html#mpi-session-set-errhandler"><span class="std std-ref">MPI_Session_set_errhandler</span></a> or at <a class="reference internal" href="MPI_Session_init.3.html#mpi-session-init"><span class="std std-ref">MPI_Session_init</span></a></p></li>
<li><p><a class="reference internal" href="MPI_Win_create_errhandler.3.html#mpi-win-create-errhandler"><span class="std std-ref">MPI_Win_create_errhandler</span></a> then <a class="reference internal" href="MPI_Win_set_errhandler.3.html#mpi-win-set-errhandler"><span class="std std-ref">MPI_Win_set_errhandler</span></a></p></li>
</ul>
<p>Note that MPI does not guarantee that an MPI program can continue past
an error.</p>
<p>See the <a class="reference internal" href="../man7/Open-MPI.7.html#open-mpi"><span class="std std-ref">MPI man page</span></a> for a full list of <a class="reference internal" href="MPI_Errors.3.html#open-mpi-errors"><span class="std std-ref">MPI error codes</span></a>.</p>
<p>See the Error Handling section of the MPI-3.1 standard for
more information.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="MPI_Gather.3.html#mpi-gather"><span class="std std-ref">MPI_Gather</span></a></p>
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