MPI_Init_thread(3) MPI MPI_Init_thread(3)NAME
MPI_Init_thread - Initialize the MPI execution environment
SYNOPSIS
int MPI_Init_thread( int *argc, char ***argv, int required, int *provided )
INPUT PARAMETERS
argc - Pointer to the number of arguments
argv - Pointer to the argument vector
required
- Level of desired thread support
OUTPUT PARAMETER
provided
- Level of provided thread support
COMMAND LINE ARGUMENTS
MPI specifies no command-line arguments but does allow an MPI implementation to make use of them. See MPI_INIT for a description of the
command line arguments supported by MPI_INIT and MPI_INIT_THREAD .
NOTES
The valid values for the level of thread support are:
MPI_THREAD_SINGLE
- Only one thread will execute.
MPI_THREAD_FUNNELED
- The process may be multi-threaded, but only the main thread will make MPI calls (all MPI calls are funneled to the main thread).
MPI_THREAD_SERIALIZED
- The process may be multi-threaded, and multiple threads may make MPI calls, but only one at a time: MPI calls are not made concur-
rently from two distinct threads (all MPI calls are serialized).
MPI_THREAD_MULTIPLE
- Multiple threads may call MPI, with no restrictions.
NOTES FOR FORTRAN
Note that the Fortran binding for this routine does not have the argc and argv arguments. ( MPI_INIT_THREAD(required, provided, ierror) )
ERRORS
All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the function and Fortran routines in
the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI
job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and
MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined
error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can
continue past an error; however, MPI implementations will attempt to continue whenever possible.
MPI_SUCCESS
- No error; MPI routine completed successfully.
MPI_ERR_OTHER
- Other error; use MPI_Error_string to get more information about this error code.
SEE ALSO
MPI_Init, MPI_Finalize
LOCATION
initthread.c
6/18/2011 MPI_Init_thread(3)
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MPI_Init_thread(3OpenMPI)MPI_Init_thread(3OpenMPI)NAME
MPI_Init_thread - Initializes the MPI execution environment
SYNTAX C Syntax
#include <mpi.h>
int MPI_Init_thread(int *argc, char ***argv,
int required, int *provided)
Fortran Syntax
INCLUDE 'mpif.h'
MPI_INIT(REQUIRED, PROVIDED, IERROR)
INTEGER REQUIRED, PROVIDED, IERROR
C++ Syntax
#include <mpi.h>
int MPI::Init_thread(int& argc, char**& argv, int required)
int MPI::Init_thread(int required)
INPUT PARAMETERS
argc C/C++ only: Pointer to the number of arguments.
argv C/C++ only: Argument vector.
required Desired level of thread support (integer).
OUTPUT PARAMETERS
provided Available level of thread support (integer).
IERROR Fortran only: Error status (integer).
DESCRIPTION
This routine, or MPI_Init, must be called before any other MPI routine (apart from MPI_Initialized) is called. MPI can be initialized at
most once; subsequent calls to MPI_Init or MPI_Init_thread are erroneous.
MPI_Init_thread, as compared to MPI_Init, has a provision to request a certain level of thread support in required:
MPI_THREAD_SINGLE Only one thread will execute.
MPI_THREAD_FUNNELED If the process is multithreaded, only the thread that called MPI_Init_thread will make MPI calls.
MPI_THREAD_SERIALIZED If the process is multithreaded, only one thread will make MPI library calls at one time.
MPI_THREAD_MULTIPLE If the process is multithreaded, multiple threads may call MPI at once with no restrictions.
The level of thread support available to the program is set in
provided, except in C++, where it is the return value of the function. In Open MPI, the value is dependent on how the library was config-
ured and built. Note that there is no guarantee that provided will be greater than or equal to required.
All MPI programs must contain a call to MPI_Init or MPI_Init_thread. Open MPI accepts the C/C++ argc and argv arguments to main, but nei-
ther modifies, interprets, nor distributes them:
{
/* declare variables */
MPI_Init_thread(&argc, &argv, req, &prov);
/* parse arguments */
/* main program */
MPI_Finalize();
}
NOTES
The Fortran version does not have provisions for argc and argv and takes only IERROR.
It is the caller's responsibility to check the value of provided, as it may be less than what was requested in required.
The MPI Standard does not say what a program can do before an MPI_Init_thread or after an MPI_Finalize. In the Open MPI implementation, it
should do as little as possible. In particular, avoid anything that changes the external state of the program, such as opening files, read-
ing standard input, or writing to standard output.
ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
tions 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.
Before the error value is returned, the current MPI error handler is 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.
SEE ALSO
MPI_Init
MPI_Initialized
MPI_Finalize
Open MPI 1.2 September 2006 MPI_Init_thread(3OpenMPI)