154 lines
4.3 KiB
Groff
154 lines
4.3 KiB
Groff
.TH MPI_Grequest_start 3 "6/5/2019" " " "MPI"
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.SH NAME
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MPI_Grequest_start \- Create and return a user-defined request
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.SH SYNOPSIS
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.nf
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int MPI_Grequest_start(MPI_Grequest_query_function * query_fn,
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MPI_Grequest_free_function * free_fn,
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MPI_Grequest_cancel_function * cancel_fn,
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void *extra_state, MPI_Request * request)
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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 query_fn
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- callback function invoked when request status is queried (function)
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.PD 1
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.PD 0
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.TP
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.B free_fn
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- callback function invoked when request is freed (function)
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.PD 1
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.PD 0
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.TP
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.B cancel_fn
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- callback function invoked when request is cancelled (function)
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.PD 1
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.PD 0
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.TP
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.B extra_state
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- Extra state passed to the above functions.
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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 request
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- Generalized request (handle)
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.PD 1
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.SH NOTES ON THE CALLBACK FUNCTIONS
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The return values from the callback functions must be a valid MPI error code
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or class. This value may either be the return value from any MPI routine
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(with one exception noted below) or any of the MPI error classes.
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For portable programs,
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.I MPI_ERR_OTHER
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may be used; to provide more
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specific information, create a new MPI error class or code with
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.I MPI_Add_error_class
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or
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.I MPI_Add_error_code
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and return that value.
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The MPI standard is not clear on the return values from the callback routines.
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However, there are notes in the standard that imply that these are MPI error
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codes. For example, pages 169 line 46 through page 170, line 1 require that
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the
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.I free_fn
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return an MPI error code that may be used in the MPI completion
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functions when they return
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.I MPI_ERR_IN_STATUS
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\&.
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The one special case is the error value returned by
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.I MPI_Comm_dup
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when
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the attribute callback routine returns a failure. The MPI standard is not
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clear on what values may be used to indicate an error return. Further,
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the Intel MPI test suite made use of non-zero values to indicate failure,
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and expected these values to be returned by the
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.I MPI_Comm_dup
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when the
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attribute routines encountered an error. Such error values may not be valid
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MPI error codes or classes. Because of this, it is the user's responsibility
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to either use valid MPI error codes in return from the attribute callbacks,
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if those error codes are to be returned by a generalized request callback,
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or to detect and convert those error codes to valid MPI error codes (recall
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that MPI error classes are valid error codes).
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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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.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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