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MPI_Testsome - Tests for completion of one or more previously initiated
communications in a list.
#include <mpi.h>
int MPI_Testsome(int incount, MPI_Request array_of_requests[],
int *outcount, int array_of_indices[],
MPI_Status array_of_statuses[])
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
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
- incount
- Length of array_of_requests (integer).
- array_of_requests
- Array of requests (array of handles).
- 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).
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.
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.
For each invocation of MPI_Testsome, if one or more
requests generate an MPI exception, only the first MPI request that caused
an exception will be passed to its corresponding error handler. No other
error handlers will be invoked (even if multiple requests generated exceptions).
However, all requests that generate an exception will have a relevant
error code set in the corresponding status.MPI_ERROR field (unless MPI_STATUSES_IGNORE
was used).
The default error handler aborts the MPI job, except for I/O
function errors. The error handler may be changed with MPI_Comm_set_errhandler,
MPI_File_set_errhandler, or MPI_Win_set_errhandler (depending on the type
of MPI handle that generated the MPI request); the predefined error handler
MPI_ERRORS_RETURN may be used to cause error values to be returned. Note
that MPI does not guarantee that an MPI program can continue past an error.
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.
In C++, if the predefined error handler MPI::ERRORS_THROW_EXCEPTIONS is
used, the value MPI::ERR_IN_STATUS will be contained in the MPI::Exception
object. The MPI_ERROR field can then be examined in the array of returned
statuses to determine exactly which request(s) generated an exception.
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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