mpi_comm_test_inter(3openmpi) [osx man page]

MPI_Comm_test_inter(3OpenMPI)											     MPI_Comm_test_inter(3OpenMPI)

NAME

       MPI_Comm_test_inter  - Tests to see if a comm is an intercommunicator.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Comm_test_inter(MPI_Comm comm, int *flag)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
	    INTEGER   COMM, IERROR
	    LOGICAL   FLAG

C++ Syntax
       #include <mpi.h>
       bool Comm::Is_inter() const

INPUT PARAMETER

       comm	 Communicator (handle).

OUTPUT PARAMETERS

       flag	(Logical.)

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       This  local routine allows the calling process to determine the type of a communicator. It returns true for an intercommunicator, false for
       an intracommunicator.

       The type of communicator also affects the value returned by three other functions.  When dealing with an intracommunicator (enables  commu-
       nication  within a single group), the functions listed below return the expected values, group size, group, and rank.  When dealing with an
       inter-communicator, however, they return the following values:

       MPI_Comm_size  Returns the size of the local group.
       MPI_Comm_group Returns the local group.
       MPI_Comm_rank  Returns the rank in the local group.

       To return the remote group and remote group size of an inter-communicator, use the  MPI_Comm_remote_group  and  MPI_Comm_remote_size  func-
       tions.

       The  operation  MPI_Comm_compare  is  valid for intercommunicators. Both communicators must be either intra- or intercommunicators, or else
       MPI_UNEQUAL results. Both corresponding local and remote groups must compare correctly to get the results MPI_CONGRUENT and MPI_SIMILAR. In
       particular, it is possible for MPI_SIMILAR to result because either the local or remote groups were similar but not identical.

       The following accessors provide consistent access to the remote group of an intercommunicator: MPI_Comm_remote_size, MPI_Comm_remote_group.

       The intercommunicator accessors (MPI_Comm_test_inter, MPI_Comm_remote_size, MPI_Comm_remote_group) are all local operations.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception  mechanism
       will be used to throw an MPI:Exception object.

       Before  the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for
       I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.

SEE ALSO

       MPI_Comm_remote_group
       MPI_Comm_remote_size
       MPI_Intercomm_create
       MPI_Intercomm_merge

Open MPI 1.2							  September 2006				     MPI_Comm_test_inter(3OpenMPI)

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MPI_Comm_size(3OpenMPI) 												   MPI_Comm_size(3OpenMPI)

NAME

       MPI_Comm_size  - Returns the size of the group associated with a communicator.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Comm_size(MPI_Comm comm, int *size)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_COMM_SIZE(COMM, SIZE, IERROR)
	    INTEGER   COMM, SIZE, IERROR

C++ Syntax
       #include <mpi.h>
       int Comm::Get_size() const

INPUT PARAMETER

       comm	 Communicator (handle).

OUTPUT PARAMETERS

       size	 Number of processes in the group of comm (integer).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       This  function indicates the number of processes involved in a communicator. For MPI_COMM_WORLD, it indicates the total number of processes
       available. This function is equivalent to accessing the communicator's group with MPI_Comm_group, computing the size using  MPI_Group_size,
       and  then  freeing  the temporary group via MPI_Group_free. If the communicator is an intra-communicator (enables communication between two
       groups), this function returns the size of the local group.  To return the size of the remote group, use the MPI_Comm_remote_size function.

       This call is often used with MPI_Comm_rank  to  determine  the  amount  of  concurrency	available  for	a  specific  library  or  program.
       MPI_Comm_rank  indicates  the  rank  of	the  process  that  calls  it in the range from  0 . . . size-1, where size is the return value of
       MPI_Comm_size.

NOTE

       MPI_COMM_NULL is not considered a valid argument to this function.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions  do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except  for
       I/O  function  errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.

SEE ALSO

       MPI_Comm_group
       MPI_Comm_rank
       MPI_Comm_compare

Open MPI 1.2							  September 2006					   MPI_Comm_size(3OpenMPI)

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mpi_comm_test_inter(3openmpi) [osx man page]

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