135 lines
3.0 KiB
Groff
135 lines
3.0 KiB
Groff
.TH MPI_Comm_compare 3 "6/5/2019" " " "MPI"
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.SH NAME
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MPI_Comm_compare \- Compares two communicators
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.SH SYNOPSIS
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.nf
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int MPI_Comm_compare(MPI_Comm comm1, MPI_Comm comm2, int *result)
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.fi
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.SH INPUT PARAMETERS
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.PD 0
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.TP
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.B comm1
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- comm1 (handle)
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.PD 1
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.PD 0
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.TP
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.B comm2
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- comm2 (handle)
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.PD 1
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.SH OUTPUT PARAMETERS
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.PD 0
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.TP
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.B result
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- integer which is
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.I MPI_IDENT
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if the contexts and groups are the
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same,
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.I MPI_CONGRUENT
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if different contexts but identical groups,
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.I MPI_SIMILAR
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if different contexts but similar groups, and
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.I MPI_UNEQUAL
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otherwise
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.PD 1
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.SH USING 'MPI_COMM_NULL' WITH 'MPI_COMM_COMPARE'
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It is an error to use
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.I MPI_COMM_NULL
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as one of the arguments to
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.I MPI_Comm_compare
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\&.
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The relevant sections of the MPI standard are
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\&.
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(2.4.1 Opaque Objects)
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A null handle argument is an erroneous
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.I IN
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argument in MPI calls, unless an
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exception is explicitly stated in the text that defines the function.
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\&.
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(5.4.1. Communicator Accessors)
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where there is no text in
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.I MPI_COMM_COMPARE
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allowing a null handle.
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.SH THREAD AND INTERRUPT SAFETY
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This routine is thread-safe. This means that this routine may be
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safely used by multiple threads without the need for any user-provided
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thread locks. However, the routine is not interrupt safe. Typically,
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this is due to the use of memory allocation routines such as
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.I malloc
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or other non-MPICH runtime routines that are themselves not interrupt-safe.
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(To perform the communicator comparisions, this routine may need to
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allocate some memory. Memory allocation is not interrupt-safe, and hence
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this routine is only thread-safe.)
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.SH NOTES FOR FORTRAN
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All MPI routines in Fortran (except for
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.I MPI_WTIME
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and
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.I MPI_WTICK
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) have
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an additional argument
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.I ierr
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at the end of the argument list.
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.I ierr
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is an integer and has the same meaning as the return value of the routine
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in C. In Fortran, MPI routines are subroutines, and are invoked with the
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.I call
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statement.
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All MPI objects (e.g.,
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.I MPI_Datatype
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,
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.I MPI_Comm
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) are of type
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.I INTEGER
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in Fortran.
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.SH ERRORS
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All MPI routines (except
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.I MPI_Wtime
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and
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.I MPI_Wtick
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) return an error value;
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C routines as the value of the function and Fortran routines in the last
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argument. Before the value is returned, the current MPI error handler is
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called. By default, this error handler aborts the MPI job. The error handler
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may be changed with
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.I MPI_Comm_set_errhandler
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(for communicators),
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.I MPI_File_set_errhandler
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(for files), and
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.I MPI_Win_set_errhandler
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(for
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RMA windows). The MPI-1 routine
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.I MPI_Errhandler_set
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may be used but
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its use is deprecated. The predefined error handler
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.I MPI_ERRORS_RETURN
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may be used to cause error values to be returned.
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Note that MPI does
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.B not
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guarentee that an MPI program can continue past
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an error; however, MPI implementations will attempt to continue whenever
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possible.
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.PD 0
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.TP
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.B MPI_SUCCESS
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- No error; MPI routine completed successfully.
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.PD 1
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.PD 0
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.TP
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.B MPI_ERR_ARG
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- Invalid argument. Some argument is invalid and is not
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identified by a specific error class (e.g.,
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.I MPI_ERR_RANK
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).
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.PD 1
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