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.TH "MPI_T_INIT_THREAD" "3" "Jul 22, 2024" "" "Open MPI"
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\fI\%MPI_T_init_thread\fP — Initializes the MPI Tool information interface
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#include <mpi.h>

int MPI_T_init_thread(int required, int *provided)
.ft P
.fi
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.SH INPUT PARAMETERS
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.IP \(bu 2
\fBrequired\fP: Desired level of thread support (integer).
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.SH OUTPUT PARAMETERS
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.IP \(bu 2
\fBprovided\fP: Available level of thread support (integer).
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.SH DESCRIPTION
.sp
MPI_T_init_thread() initializes the MPI tool information interface.
Calls to MPI tool functions are allowed at any point in execution
(including before MPI_Init() and after MPI_Finalize()) as long
as MPI_T_init_thread() has been called at least once and the number
of calls to MPI_T_init_thread() is greater than the number of calls
to MPI_T_finalize(). If at any point in execution the number of
calls to MPI_T_finalize() equals the number of calls to
MPI_T_init_thread() the MPI tool interface will no longer be
available until another call to MPI_T_init_thread().
.sp
MPI_T_init_thread(), like MPI_Init_thread(), has a provision to
request a certain level of thread support in \fBrequired\fP:
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.IP \(bu 2
\fBMPI_THREAD_SINGLE\fP: Only one thread will execute.
.IP \(bu 2
\fBMPI_THREAD_FUNNELED\fP: If the process is multithreaded, only the
thread that called \fI\%MPI_Init_thread\fP will make MPI calls.
.IP \(bu 2
\fBMPI_THREAD_SERIALIZED\fP: If the process is multithreaded, only one
thread will make MPI library calls at one time.
.IP \(bu 2
\fBMPI_THREAD_MULTIPLE\fP: If the process is multithreaded, multiple
threads may call MPI at once with no restrictions.
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.sp
The level of thread support available to the program is set in
\fBprovided\fP\&. In Open MPI, the value is dependent on how the library was
configured and built. Note that there is no guarantee that \fBprovided\fP
will be greater than or equal to \fBrequired\fP\&.
.SH NOTES
.sp
It is the caller’s responsibility to check the value of \fBprovided\fP, as
it may be less than what was requested in \fBrequired\fP\&.
.SH ERRORS
.sp
\fI\%MPI_T_init_thread\fP will fail if:
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.IP \(bu 2
\fBMPI_T_ERR_MEMORY\fP: Out of memory
.IP \(bu 2
\fBMPI_T_ERR_CANNOT_INIT\fP: Interface not in the state to be
initialized
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.sp
\fBSEE ALSO:\fP
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.INDENT 3.5
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.IP \(bu 2
\fI\%MPI_T\fP
.IP \(bu 2
\fI\%MPI_Init\fP
.IP \(bu 2
\fI\%MPI_Init_thread\fP
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.SH COPYRIGHT
2003-2024, The Open MPI Community
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