c4c69b4ddf
Add support for MPI_Count type and MPI_COUNT datatype and add the required MPI-3 functions MPI_Get_elements_x, MPI_Status_set_elements_x, MPI_Type_get_extent_x, MPI_Type_get_true_extent_x, and MPI_Type_size_x. This commit adds only the C bindings. Fortran bindins will be added in another commit. For now the MPI_Count type is define to have the same size as MPI_Offset. The type is required to be at least as large as MPI_Offset and MPI_Aint. The type was initially intended to be a ssize_t (if it was the same size as a long long) but there were issues compiling romio with that definition (despite the inclusion of stddef.h). I updated the datatype engine to use size_t instead of uint32_t to support large datatypes. This will require some review to make sure that 1) the changes are beneficial, 2) nothing was broken by the change (I doubt anything was), and 3) there are no performance regressions due to this change. Increase the maximum number of predifined datatypes to support MPI_Count Put common get_elements code to ompi/datatype/ompi_datatype_get_elements.c Update MPI_Get_count to reflect changes in MPI-3 (return MPI_UNDEFINED when the count is too large for an int) This commit was SVN r28932.
105 строки
4.4 KiB
Plaintext
105 строки
4.4 KiB
Plaintext
.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
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.\" Copyright 2010 Cisco Systems, Inc. All rights reserved.
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.\" Copyright 2006-2008 Sun Microsystems, Inc.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.TH MPI_Get_elements 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fBMPI_Get_elements, MPI_Get_elements_x\fP \- Returns the number of basic elements in a data type.
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.SH SYNTAX
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.ft R
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.SH C Syntax
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.nf
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#include <mpi.h>
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int MPI_Get_elements(MPI_Status *\fIstatus\fP, MPI_Datatype\fI datatype\fP,
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int\fI *count\fP)
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int MPI_Get_elements_x(MPI_Status *\fIstatus\fP, MPI_Datatype\fI datatype\fP,
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MPI_Count\fI *count\fP)
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.fi
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_GET_ELEMENTS(\fISTATUS, DATATYPE, COUNT, IERROR\fP)
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INTEGER \fISTATUS(MPI_STATUS_SIZE), DATATYPE, COUNT, IERROR\fP
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MPI_GET_ELEMENTS_X(\fISTATUS, DATATYPE, COUNT, IERROR\fP)
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INTEGER \fISTATUS(MPI_STATUS_SIZE), DATATYPE\fP
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INTEGER(KIND=MPI_COUNT_KIND) \fICOUNT\fP
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INTEGER \fIIERROR\fP
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.fi
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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int Status::Get_elements(const Datatype& \fIdatatype\fP) const
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.fi
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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status
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Return status of receive operation (status).
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.TP 1i
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datatype
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Datatype used by receive operation (handle).
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.SH OUTPUT PARAMETERS
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.ft R
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count Number of received basic elements (integer).
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.ft R
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.TP 1i
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IERROR
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Fortran only: Error status (integer).
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.SH DESCRIPTION
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.ft R
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MPI_Get_elements and MPI_Get_elements_x behave different from MPI_Get_count, which returns the number of "top-level entries" received, i.e., the number of "copies" of type datatype. MPI_Get_count may return any integer value k, where 0 =< k =< count. If MPI_Get_count returns k, then the number of basic elements received (and the value returned by MPI_Get_elements and MPI_Get_elements_x) is n * k, where n is the number of basic elements in the type map of datatype. If the number of basic elements received is not a multiple of n, that is, if the receive operation has not received an integral number of datatype "copies," then MPI_Get_count returns the value MPI_UNDEFINED. For both functions, if the \fIcount\fP parameter cannot express the value to be returned (e.g., if the parameter is too small to hold the output value), it is set to MPI_UNDEFINED.
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.sp
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\fBExample:\fP Usage of MPI_Get_count and MPI_Get_element:
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.sp
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.nf
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\&...
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CALL MPI_TYPE_CONTIGUOUS(2, MPI_REAL, Type2, ierr)
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CALL MPI_TYPE_COMMIT(Type2, ierr)
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\&...
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CALL MPI_COMM_RANK(comm, rank, ierr)
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IF(rank.EQ.0) THEN
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CALL MPI_SEND(a, 2, MPI_REAL, 1, 0, comm, ierr)
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CALL MPI_SEND(a, 3, MPI_REAL, 1, 0, comm, ierr)
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ELSE
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CALL MPI_RECV(a, 2, Type2, 0, 0, comm, stat, ierr)
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CALL MPI_GET_COUNT(stat, Type2, i, ierr) ! returns i=1
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CALL MPI_GET_ELEMENTS(stat, Type2, i, ierr) ! returns i=2
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CALL MPI_RECV(a, 2, Type2, 0, 0, comm, stat, ierr)
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CALL MPI_GET_COUNT(stat, Type2, i, ierr) ! returns i=MPI_UNDEFINED
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CALL MPI_GET_ELEMENTS(stat, Type2, i, ierr) ! returns i=3
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END IF
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.fi
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.sp
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The function MPI_Get_elements can also be used after a probe to find the number of elements in the probed message. Note that the two functions MPI_Get_count and MPI_Get_elements return the same values when they are used with primitive data types.
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.SH ERRORS
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Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions 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.
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.sp
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Before the error value is returned, the current MPI error handler is
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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.
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.SH FORTRAN 77 NOTES
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.ft R
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The MPI standard prescribes portable Fortran syntax for
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the \fICOUNT\fP argument of MPI_Get_elements_x only for
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Fortran 90. FORTRAN 77 users may use the non-portable syntax
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.sp
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.nf
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INTEGER*MPI_COUNT_KIND \fICOUNT\fP
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.fi
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.sp
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where MPI_COUNT_KIND is a constant defined in mpif.h
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and gives the length of the declared integer in bytes.
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.SH SEE ALSO
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.ft R
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.sp
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MPI_Get_count
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