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.TH "MPI_TESTSOME" "3" "May 30, 2025" "" "Open MPI"
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\fI\%MPI_Testsome\fP — Tests for completion of one or more previously
initiated communications in a list.
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#include <mpi.h>

int MPI_Testsome(int incount, MPI_Request array_of_requests[],
     int *outcount, int array_of_indices[],
     MPI_Status array_of_statuses[])
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_TESTSOME(INCOUNT, ARRAY_OF_REQUESTS, OUTCOUNT,
             ARRAY_OF_INDICES, ARRAY_OF_STATUSES, IERROR)
     INTEGER INCOUNT, ARRAY_OF_REQUESTS(*)
     INTEGER OUTCOUNT, ARRAY_OF_INDICES(*)
     INTEGER ARRAY_OF_STATUSES(MPI_STATUS_SIZE,*), IERROR
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran 2008 Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE mpi_f08
MPI_Testsome(incount, array_of_requests, outcount, array_of_indices,
             array_of_statuses, ierror)
     INTEGER, INTENT(IN) :: incount
     TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(incount)
     INTEGER, INTENT(OUT) :: outcount, array_of_indices(*)
     TYPE(MPI_Status) :: array_of_statuses(*)
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
.ft P
.fi
.UNINDENT
.UNINDENT
.SH INPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBincount\fP: Length of array_of_requests (integer).
.IP \(bu 2
\fBarray_of_requests\fP: Array of requests (array of handles).
.UNINDENT
.SH OUTPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBoutcount\fP: Number of completed requests (integer).
.IP \(bu 2
\fBarray_of_indices\fP: Array of indices of operations that completed (array of integers).
.IP \(bu 2
\fBarray_of_statuses\fP: Array of status objects for operations that completed (array of status).
.IP \(bu 2
\fBierror\fP: Fortran only: Error status (integer).
.UNINDENT
.SH DESCRIPTION
.sp
Behaves like \fI\%MPI_Waitsome\fP, except that it returns immediately.
.sp
Returns in outcount the number of requests from the list
array_of_requests that have completed. Returns in the first outcount
locations of the array array_of_indices the indices of these operations
(index within the array array_of_requests; the array is indexed from 0
in C and from 1 in Fortran). Returns in the first outcount locations of
the array array_of_status the status for these completed operations. If
a request that completed was allocated by a nonblocking communication
call, then it is deallocated, and the associated handle is set to
MPI_REQUEST_NULL.
.sp
If no operation has completed it returns outcount = 0. If there is no
active handle in the list, it returns outcount = MPI_UNDEFINED.
.sp
\fI\%MPI_Testsome\fP is a local operation, which returns immediately, whereas
\fI\%MPI_Waitsome\fP blocks until a communication completes, if it was passed a
list that contains at least one active handle. Both calls fulfill a
fairness requirement: If a request for a receive repeatedly appears in a
list of requests passed to \fI\%MPI_Waitsome\fP or \fI\%MPI_Testsome\fP, and a matching
send has been posted, then the receive will eventually succeed unless
the send is satisfied by another receive; send requests also fulfill
this fairness requirement.
.sp
Errors that occur during the execution of \fI\%MPI_Testsome\fP are handled as
for \fI\%MPI_Waitsome\fP\&.
.sp
If your application does not need to examine the \fIarray_of_statuses\fP
field, you can save resources by using the predefined constant
MPI_STATUSES_IGNORE can be used as a special value for the
\fIarray_of_statuses\fP argument.
.SH NOTES
.sp
The use of \fI\%MPI_Testsome\fP is likely to be more efficient than the use of
\fI\%MPI_Testany\fP\&. The former returns information on all completed
communications; with the latter, a new call is required for each
communication that completes.
.sp
A server with multiple clients can use \fI\%MPI_Waitsome\fP so as not to starve
any client. Clients send messages to the server with service requests.
The server calls \fI\%MPI_Waitsome\fP with one receive request for each client,
then handles all receives that have completed. If a call to \fI\%MPI_Waitany\fP
is used instead, then one client could starve while requests from
another client always sneak in first.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
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
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
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.
.sp
Open MPI includes three predefined error handlers that can be used:
.INDENT 0.0
.IP \(bu 2
\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP 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.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
.UNINDENT
.sp
MPI applications can also implement their own error handlers by calling:
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.sp
Note that MPI does not guarantee that an MPI program can continue past
an error.
.sp
See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
.sp
See the Error Handling section of the MPI\-3.1 standard for
more information.
.sp
For each invocation of \fI\%MPI_Testsome\fP, if one or more requests
generate an MPI error, only the \fIfirst\fP MPI request that caused an
error will be passed to its corresponding error handler. No other
error handlers will be invoked (even if multiple requests generated
errors). However, \fIall\fP requests that generate an error will have a
relevant error code set in the corresponding \fBstatus.MPI_ERROR\fP
field (unless \fBMPI_STATUSES_IGNORE\fP was used).
.sp
If the invoked error handler allows \fI\%MPI_Testsome\fP to return to
the caller, the value \fBMPI_ERR_IN_STATUS\fP will be returned in the C
and Fortran bindings.
.sp
\fBSEE ALSO:\fP
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Test\fP
.IP \(bu 2
\fI\%MPI_Testall\fP
.IP \(bu 2
\fI\%MPI_Testany\fP
.IP \(bu 2
\fI\%MPI_Wait\fP
.IP \(bu 2
\fI\%MPI_Waitall\fP
.IP \(bu 2
\fI\%MPI_Waitany\fP
.IP \(bu 2
\fI\%MPI_Waitsome\fP
.IP \(bu 2
\fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.UNINDENT
.UNINDENT
.SH COPYRIGHT
2003-2025, The Open MPI Community
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