plucky (3) MPI_Testsome.openmpi.3.gz
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Testsome(int incount, MPI_Request array_of_requests[],
int *outcount, int array_of_indices[],
MPI_Status array_of_statuses[])
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
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
Fortran 2008 Syntax
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
INPUT PARAMETERS
• incount: Length of array_of_requests (integer).
• array_of_requests: Array of requests (array of handles).
OUTPUT PARAMETERS
• outcount: Number of completed requests (integer).
• array_of_indices: Array of indices of operations that completed (array of integers).
• array_of_statuses: Array of status objects for operations that completed (array of status).
• ierror: Fortran only: Error status (integer).
DESCRIPTION
Behaves like MPI_Waitsome, except that it returns immediately.
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.
If no operation has completed it returns outcount = 0. If there is no active handle in the list, it
returns outcount = MPI_UNDEFINED.
MPI_Testsome is a local operation, which returns immediately, whereas MPI_Waitsome 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 MPI_Waitsome or MPI_Testsome, 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.
Errors that occur during the execution of MPI_Testsome are handled as for MPI_Waitsome.
If your application does not need to examine the array_of_statuses field, you can save resources by using
the predefined constant MPI_STATUSES_IGNORE can be used as a special value for the array_of_statuses
argument.
NOTES
The use of MPI_Testsome is likely to be more efficient than the use of MPI_Testany. The former returns
information on all completed communications; with the latter, a new call is required for each
communication that completes.
A server with multiple clients can use MPI_Waitsome so as not to starve any client. Clients send messages
to the server with service requests. The server calls MPI_Waitsome with one receive request for each
client, then handles all receives that have completed. If a call to MPI_Waitany is used instead, then one
client could starve while requests from another client always sneak in first.
ERRORS
Almost all MPI routines return an error value; C routines as the return result of the function and
Fortran routines in the last argument.
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 MPI_Init/MPI_Init_thread, after
MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler.
The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using
the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
MPI_Comm_spawn_multiple. 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.
Open MPI includes three predefined error handlers that can be used:
• MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.
• MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a
window or file, acts as if MPI_Abort 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.
• MPI_ERRORS_RETURN Returns an error code to the application.
MPI applications can also implement their own error handlers by calling:
• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
• MPI_File_create_errhandler then MPI_File_set_errhandler
• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
• MPI_Win_create_errhandler then MPI_Win_set_errhandler
Note that MPI does not guarantee that an MPI program can continue past an error.
See the MPI man page for a full list of MPI error codes.
See the Error Handling section of the MPI-3.1 standard for more information.
For each invocation of MPI_Testsome, if one or more requests generate an MPI error, only the first 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, all requests that generate an
error will have a relevant error code set in the corresponding status.MPI_ERROR field (unless
MPI_STATUSES_IGNORE was used).
If the invoked error handler allows MPI_Testsome to return to the caller, the value MPI_ERR_IN_STATUS
will be returned in the C and Fortran bindings.
SEE ALSO:
• MPI_Comm_set_errhandler
• MPI_File_set_errhandler
• MPI_Test
• MPI_Testall
• MPI_Testany
• MPI_Wait
• MPI_Waitall
• MPI_Waitany
• MPI_Waitsome
• MPI_Win_set_errhandler
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2003-2025, The Open MPI Community
Feb 17, 2025 MPI_TESTSOME(3)