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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
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<A NAME="MatSetSizes"><H1>MatSetSizes</H1></A>
Sets the local and global sizes, and checks to determine compatibility
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
PetscErrorCode MatSetSizes(Mat A, PetscInt m, PetscInt n, PetscInt M, PetscInt N)
</PRE>
Collective on <A HREF="../Mat/Mat.html#Mat">Mat</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>A </B></TD><TD>- the matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>m </B></TD><TD>- number of local rows (or <A HREF="../Sys/PETSC_DECIDE.html#PETSC_DECIDE">PETSC_DECIDE</A>)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>n </B></TD><TD>- number of local columns (or <A HREF="../Sys/PETSC_DECIDE.html#PETSC_DECIDE">PETSC_DECIDE</A>)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>M </B></TD><TD>- number of global rows (or <A HREF="../Sys/PETSC_DETERMINE.html#PETSC_DETERMINE">PETSC_DETERMINE</A>)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>N </B></TD><TD>- number of global columns (or <A HREF="../Sys/PETSC_DETERMINE.html#PETSC_DETERMINE">PETSC_DETERMINE</A>)
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
m (n) and M (N) cannot be both <A HREF="../Sys/PETSC_DECIDE.html#PETSC_DECIDE">PETSC_DECIDE</A>
If one processor calls this with M (N) of <A HREF="../Sys/PETSC_DECIDE.html#PETSC_DECIDE">PETSC_DECIDE</A> then all processors must, otherwise the program will hang.
<P>
If <A HREF="../Sys/PETSC_DECIDE.html#PETSC_DECIDE">PETSC_DECIDE</A> is not used for the arguments 'm' and 'n', then the
user must ensure that they are chosen to be compatible with the
vectors. To do this, one first considers the matrix-vector product
'y = A x'. The 'm' that is used in the above routine must match the
local size used in the vector creation routine <A HREF="../Vec/VecCreateMPI.html#VecCreateMPI">VecCreateMPI</A>() for 'y'.
Likewise, the 'n' used must match that used as the local size in
<A HREF="../Vec/VecCreateMPI.html#VecCreateMPI">VecCreateMPI</A>() for 'x'.
<P>
You cannot change the sizes once they have been set.
<P>
The sizes must be set before <A HREF="../Mat/MatSetUp.html#MatSetUp">MatSetUp</A>() or MatXXXSetPreallocation() is called.
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatGetSize.html#MatGetSize">MatGetSize</A>(), <A HREF="../Sys/PetscSplitOwnership.html#PetscSplitOwnership">PetscSplitOwnership</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>beginner
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/mat/utils/gcreate.c.html#MatSetSizes">src/mat/utils/gcreate.c</A>
<BR><A HREF="./index.html">Index of all Mat routines</A>
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<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/mat/examples/tutorials/ex2.c.html">src/mat/examples/tutorials/ex2.c.html</A><BR>
<A HREF="../../../src/mat/examples/tutorials/ex5.c.html">src/mat/examples/tutorials/ex5.c.html</A><BR>
<A HREF="../../../src/mat/examples/tutorials/ex8.c.html">src/mat/examples/tutorials/ex8.c.html</A><BR>
<A HREF="../../../src/mat/examples/tutorials/ex15.c.html">src/mat/examples/tutorials/ex15.c.html</A><BR>
<A HREF="../../../src/mat/examples/tutorials/ex16.c.html">src/mat/examples/tutorials/ex16.c.html</A><BR>
<A HREF="../../../src/mat/examples/tutorials/ex17.c.html">src/mat/examples/tutorials/ex17.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex1.c.html">src/ksp/ksp/examples/tutorials/ex1.c.html</A><BR>
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