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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[])
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
#include <mpi.h>
static int Request::Testsome(int incount, Request
array_of_requests[], int array_of_indices[], Status array_of_statuses[])
static int Request::Testsome(int incount, Request
array_of_requests[], int array_of_indices[])
- 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. 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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