MPIInitthread(3OpenMPI) MPIInitthread(3OpenMPI)

NAME
       MMPPIIIInniitttthhrreeaadd - Initializes the MPI execution environment


SSYYNNTTAAXX
CC SSyynnttaaxx
       #include 
       int MPIInitthread(int *argc, char ***argv,
            int required, int *provided)


FFoorrttrraann SSyynnttaaxx
       INCLUDE 'mpif.h'
       MPIINIT(REQUIRED, PROVIDED, IERROR)
            INTEGER   REQUIRED, PROVIDED, IERROR


CC++++ SSyynnttaaxx
       #include 
       int MPI::Initthread(int& argc, char**& argv, int required)
       int MPI::Initthread(int required)


IINNPPUUTT PPAARRAAMMEETTEERRSS
       argc      C/C++ only: Pointer to the number of arguments.

       argv      C/C++ only: Argument vector.

       required  Desired level of thread support (integer).


OOUUTTPPUUTT PPAARRAAMMEETTEERRSS
       provided  Available level of thread support (integer).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       This  routine, or MPIInit, must be called before any other MPI routine
       (apart from MPIInitialized) is called. MPI can be initialized at  most
       once; subsequent calls to MPIInit or MPIInitthread are erroneous.

       MPIInitthread,  as compared to MPIInit, has a provision to request a
       certain level of thread support in required:

       MPITHREADSINGLE       Only one thread will execute.

       MPITHREADFUNNELED     If  the  process  is  multithreaded,  only  the
                               thread  that  called  MPIInitthread will make
                               MPI calls.

       MPITHREADSERIALIZED   If  the  process  is  multithreaded,  only  one
                               thread will make MPI library calls at one time.

       MPITHREADMULTIPLE     If  the  process  is  multithreaded,   multiple
                               threads  may  call MPI at once with no restric-
                               tions.

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 configured
       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 MPIInit or MPIInitthread.
       Open MPI accepts the C/C++ argc and argv arguments to main, but neither
       modifies, interprets, nor distributes them:

            {
                 /* declare variables */
                 MPIInitthread(&argc, &argv, req, &prov);
                 /* parse arguments */
                 /* main program */
                 MPIFinalize();
            }


NNOOTTEESS
       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
       MPIInitthread or after an MPIFinalize. In the Open  MPI  implementa-
       tion, it should do as little as possible. In particular, avoid anything
       that changes the external state of the program, such as opening  files,
       reading standard input, or writing to standard output.


EERRRROORRSS
       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::ERRORSTHROWEXCEPTIONS, 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
       MPICommseterrhandler; the predefined error handler MPIERRORSRETURN
       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
       MPIInit
       MPIInitialized
       MPIFinalize




Open MPI 1.2                    September 2006       MPIInitthread(3OpenMPI)