MPI_PROBE, MPI_Probe

Purpose

Waits until a message matching source, tag, and comm arrives.

C synopsis

#include <mpi.h>
int MPI_Probe(int source,int tag,MPI_Comm comm,MPI_Status *status);

C++ synopsis

#include mpi.h
void MPI::Comm::Probe(int source, int tag) const;

#include mpi.h
void MPI::Comm::Probe(int source, int tag, MPI::Status& status) const;

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_PROBE(INTEGER SOURCE,INTEGER TAG,INTEGER COMM,
          INTEGER STATUS(MPI_STATUS_SIZE),INTEGER IERROR)

Description

MPI_PROBE behaves like MPI_IPROBE. It lets you check for an incoming
message without actually receiving it. MPI_PROBE is different in that it is
a blocking call that returns only after a matching message has been found.

Passing MPI_STATUS_IGNORE for the status argument causes PE MPI to skip
filling in the status fields. By passing this value for status, you can
avoid having to allocate a status object in programs that do not need to
examine the status fields.

Parameters

source
     is a source rank or MPI_ANY_SOURCE (integer) (IN)
tag
     is a source tag or MPI_ANY_TAG (positive integer) (IN)
comm
     is a communicator (handle) (IN)
status
     is a status object (Status) (INOUT). Note that in FORTRAN a single
     status object is an array of integers.
IERROR
     is the FORTRAN return code. It is always the last argument.

Notes

In a threads environment, MPI_PROBE or MPI_IPROBE followed by MPI_RECV,
based on the information from the probe, may not be a thread-safe
operation. You must make sure that no other thread received the detected
message.

An MPI_IPROBE cannot prevent a message from being cancelled successfully by
the sender, making it unavailable for the MPI_RECV. Structure your program
so this will not occur.

Errors

Invalid source
     source < 0 or source > = groupsize

Invalid status ignore value

Invalid tag
     tag < 0

Invalid communicator

MPI not initialized

MPI already finalized

Related information

     MPI_IPROBE
     MPI_RECV