MPI_Testsome(3) Open MPI MPI_Testsome(3)NAMEMPI_Testsome - Tests for completion of one or more previously initiated
communications in a list.
SYNTAXC 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
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
C++ Syntax
#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[])
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 inte‐
gers).
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. 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 match‐
ing 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_STA‐
TUSES_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 communica‐
tions; 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
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 han‐
dlers 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 con‐
tinue past an error.
If the invoked error handler allows MPI_Testsome to return to the call‐
er, 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.
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
1.7.4 Feb 04, 2014 MPI_Testsome(3)
