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MPI_Init_thread(3): update refs about MPI_THREAD_MULTIPLE #8399

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Jan 20, 2021
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MPI_Init_thread(3): update refs about MPI_THREAD_MULTIPLE #8399

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45 changes: 10 additions & 35 deletions ompi/mpi/man/man3/MPI_Init_thread.3in
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
.\" -*- nroff -*-
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" Copyright (c) 2010-2015 Cisco Systems, Inc. All rights reserved.
.\" Copyright (c) 2010-2020 Cisco Systems, Inc. All rights reserved.
.\" Copyright (c) 2020 Google, LLC. All rights reserved.
.\" $COPYRIGHT$
.TH MPI_Init_thread 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
Expand Down Expand Up @@ -128,52 +128,27 @@ opening files, reading standard input, or writing to standard output.
.
.SH MPI_THREAD_MULTIPLE Support
.
MPI_THREAD_MULTIPLE support is included if Open MPI was configured
with the --enable-mpi-thread-multiple configure switch. You can check the
MPI_THREAD_MULTIPLE support is included if the environment in which
Open MPI was built supports threading. You can check the
output of
.BR ompi_info (1)
to see if Open MPI has MPI_THREAD_MULTIPLE support:
.
.PP
.nf
shell$ ompi_info | grep -i thread
Thread support: posix (mpi: yes, progress: no)
shell$ ompi_info | grep "Thread support"
Thread support: posix (MPI_THREAD_MULTIPLE: yes, OPAL support: yes, OMPI progress: no, Event lib: yes)
shell$
.fi
.
.PP
The "mpi: yes" portion of the above output indicates that Open MPI was
compiled with MPI_THREAD_MULTIPLE support.
The "MPI_THREAD_MULTIPLE: yes" portion of the above output indicates
that Open MPI was compiled with MPI_THREAD_MULTIPLE support.
.
.PP
Note that MPI_THREAD_MULTIPLE support is only lightly tested. It
likely does not work for thread-intensive applications. Also note
that
.I only
the MPI point-to-point communication functions for the BTL's listed
below are considered thread safe. Other support functions (e.g., MPI
attributes) have not been certified as safe when simultaneously used
by multiple threads.
.
.PP
.nf
tcp
sm
mx
elan
self
.fi
.
.PP
Note that Open MPI's thread support is in a fairly early stage; the
above devices are likely to
.IR work ,
but the latency is likely to be fairly high. Specifically, efforts so
far have concentrated on
.IR correctness ,
not
.I performance
(yet).
Note that there is a small performance penalty for using
MPI_THREAD_MULTIPLE support; latencies for short messages will be
higher as compared to when using MPI_THREAD_SINGLE, for example.
.
.
.SH ERRORS
Expand Down