40a2bfa238
This merges the branch containing the revamped build system based around converting autogen from a bash script to a Perl program. Jeff has provided emails explaining the features contained in the change. Please note that configure requirements on components HAVE CHANGED. For example. a configure.params file is no longer required in each component directory. See Jeff's emails for an explanation. This commit was SVN r23764.
186 строки
5.0 KiB
Plaintext
186 строки
5.0 KiB
Plaintext
. -*- nroff -*-
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.\"Copyright 2006-2008 Sun Microsystems, Inc.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.\" Copyright (c) 2010 Cisco Systems, Inc. All rights reserved.
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.TH MPI_Init_thread 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.
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.SH NAME
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\fBMPI_Init_thread\fP \- Initializes the MPI execution environment
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.
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.SH SYNTAX
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.ft R
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.
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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_Init_thread(int *\fIargc\fP, char ***\fIargv\fP,
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int \fIrequired\fP, int *\fIprovided\fP)
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_INIT(\fIREQUIRED, PROVIDED, IERROR\fP)
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INTEGER \fIREQUIRED, PROVIDED, IERROR\fP
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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::Init_thread(int& \fIargc\fP, char**& \fIargv\fP, int \fIrequired\fP)
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int MPI::Init_thread(int \fIrequired\fP)
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.SH INPUT PARAMETERS
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.ft R
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.TP 1i
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argc
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C/C++ only: Pointer to the number of arguments.
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.TP 1i
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argv
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C/C++ only: Argument vector.
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.TP 1i
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required
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Desired level of thread support (integer).
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.
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.
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.SH OUTPUT PARAMETERS
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.ft R
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.TP 1i
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provided
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Available level of thread support (integer).
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.TP 1i
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IERROR
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Fortran only: Error status (integer).
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.
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.
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.SH DESCRIPTION
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.ft R
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This routine, or MPI_Init, must be called before any other MPI routine
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(apart from MPI_Initialized) is called. MPI can be initialized at most
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once; subsequent calls to MPI_Init or MPI_Init_thread are erroneous.
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.sp
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MPI_Init_thread, as compared to MPI_Init, has a provision to request a
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certain level of thread support in \fIrequired\fP:
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.TP 2.4i
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MPI_THREAD_SINGLE
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Only one thread will execute.
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.TP 2.4i
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MPI_THREAD_FUNNELED
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If the process is multithreaded, only the thread that called
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MPI_Init_thread will make MPI calls.
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.TP 2.4i
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MPI_THREAD_SERIALIZED
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If the process is multithreaded, only one thread will make MPI library
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calls at one time.
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.TP 2.4i
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MPI_THREAD_MULTIPLE
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If the process is multithreaded, multiple threads may call MPI at once
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with no restrictions.
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.
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.PP
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The level of thread support available to the program is set in
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\fIprovided\fP, except in C++, where it is the return value of the
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function. In Open MPI, the value is dependent on how the library was configured and built. Note that there is no guarantee that \fIprovided\fP will be greater than or equal to
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\fIrequired\fP.
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.sp
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All MPI programs must contain a call to MPI_Init or
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MPI_Init_thread. Open MPI accepts the C/C++ \fIargc\fP and \fIargv\fP
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arguments to main, but neither modifies, interprets, nor distributes
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them:
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.sp
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.nf
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{
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/* declare variables */
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MPI_Init_thread(&argc, &argv, req, &prov);
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/* parse arguments */
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/* main program */
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MPI_Finalize();
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}
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.fi
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.
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.SH NOTES
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.ft R
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The Fortran version does not have provisions for \fIargc\fP and
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\fIargv\fP and takes only IERROR.
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.sp
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It is the caller's responsibility to check the value of \fIprovided\fP,
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as it may be less than what was requested in \fIrequired\fP.
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.sp
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The MPI Standard does not say what a program can do before an
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MPI_Init_thread or after an MPI_Finalize. In the Open MPI
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implementation, it should do as little as possible. In particular,
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avoid anything that changes the external state of the program, such as
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opening files, reading standard input, or writing to standard output.
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.
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.
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.SH MPI_THREAD_MULTIPLE Support
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.
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MPI_THREAD_MULTIPLE support is included if Open MPI was configured
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with the --enable-thread-multiple configure switch. You can check the
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output of
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.BR ompi_info (1)
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to see if Open MPI has MPI_THREAD_MULTIPLE support:
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.
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.PP
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.nf
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shell$ ompi_info | grep -i thread
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Thread support: posix (mpi: yes, progress: no)
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shell$
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.fi
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.
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.PP
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The "mpi: yes" portion of the above output indicates that Open MPI was
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compiled with MPI_THREAD_MULTIPLE support.
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.
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.PP
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Note that MPI_THREAD_MULTIPLE support is only lightly tested. It
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likely does not work for thread-intensive applications. Also note
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that
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.I only
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the MPI point-to-point communication functions for the BTL's listed
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below are considered thread safe. Other support functions (e.g., MPI
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attributes) have not been certified as safe when simultaneously used
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by multiple threads.
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.
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.PP
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.nf
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tcp
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sm
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mx
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elan
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self
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.fi
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.
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.PP
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Note that Open MPI's thread support is in a fairly early stage; the
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above devices are likely to
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.IR work ,
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but the latency is likely to be fairly high. Specifically, efforts so
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far have concentrated on
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.IR correctness ,
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not
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.I performance
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(yet).
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.
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.
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.SH ERRORS
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.ft R
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Almost all MPI routines return an error value; C routines as
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the value of the function and Fortran routines in the last argument. C++
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functions do not return errors. If the default error handler is set to
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MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
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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
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I/O function errors. The error handler may be changed with
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MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
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may be used to cause error values to be returned. Note that MPI does not
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guarantee that an MPI program can continue past an error.
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.
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.SH SEE ALSO
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.ft R
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.nf
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MPI_Init
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MPI_Initialized
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MPI_Finalize
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