NAME

       MPI_Init_thread -  Initialize the MPI execution environment

SYNOPSIS

       #include <mpi.h>
       int
       MPI_Init_thread(int *pargc, char ***pargv, int requested, int *pprovided)

INPUT PARAMETERS

       pargc  - Pointer to the number of arguments
       pargv  - Pointer to the argument vector
       requested
              - Desired level of thread support
       pprovided
              - Given level of thread support

NOTES

       LAM currently supports MPI_THREAD_SINGLE , MPI_THREAD_SERIALIZED , and MPI_THREAD_FUNNELED
       .  MPI_THREAD_MULTIPLE is not yet supported.  The use of  MPI_INIT_THREAD  is  recommended
       instead  of  MPI_INIT  if  an  MPI  program  is  going to be multi-threaded.  However, the
       LAM_MPI_THREAD_LEVEL environment variable can be used to the same effect.  See MPI_Init(3)
       for more details.

       There  is currently no distinction between MPI_THREAD_SINGLE and MPI_THREAD_FUNNELED .  An
       application using MPI_THREAD_FUNNELED promises to never call MPI from a  different  thread
       than  the one that invoked MPI_INIT (or MPI_INIT_THREAD ).  LAM does no checking to ensure
       that this is true.  As such, no locks are placed around MPI calls to ensure that only  one
       thread  is  making  MPI  calls at a time (since the application has promised that only one
       thread will be making MPI calls).

       Using MPI_THREAD_SERIALIZED will cause LAM to place locks around all MPI calls  such  that
       only  one  thread will be able to enter the MPI library at a time; beware of this fact for
       portability with other MPI implementations.  Even with multiple threads, deadlock is still
       possible  when  using MPI_THREAD_SERIALIZED -- applications still need to be aware of this
       and code appropriately.

       Other  than  this  restriction,  this  function  behaves  identically  to  MPI_INIT   (see
       MPI_Init(3)).

       Note  that  both  MPI_INIT and MPI_INIT_THREAD are allowed to changed the requested thread
       level based on lower-level device and SSI module initializations.  For example, if a  user
       application  invokes MPI_Init , some SSI modules may require threads and therefore upgrade
       the thread support level to something higher than MPI_THREAD_SINGLE .

ERRORS

       If an error occurs in an MPI function, the current MPI error handler is called  to  handle
       it.   By default, this error handler aborts the MPI job.  The error handler may be changed
       with MPI_Errhandler_set ; the predefined error handler MPI_ERRORS_RETURN may  be  used  to
       cause  error values to be returned (in C and Fortran; this error handler is less useful in
       with the C++ MPI bindings.   The  predefined  error  handler  MPI::ERRORS_THROW_EXCEPTIONS
       should  be  used in C++ if the error value needs to be recovered).  Note that MPI does not
       guarantee that an MPI program can continue past an error.

       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.  The C++ bindings for
       MPI do not return error  values;  instead,  error  values  are  communicated  by  throwing
       exceptions of type MPI::Exception (but not by default).  Exceptions are only thrown if the
       error value is not MPI::SUCCESS .

       Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return
       upon an error, there will be no way to recover what the actual error value was.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_ARG
              -  Invalid  argument.  Some argument is invalid and is not identified by a specific
              error class.  This is typically a NULL pointer or other such error.
       MPI_ERR_OTHER
              - This error class is associated with an error code that indicates that an  attempt
              was  made  to  call  MPI_INIT a second time.  MPI_INIT may only be called once in a
              program.
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

SEE ALSO

       MPI_Init, MPI_Finalize, lamboot, mpirun, lamhalt, lamssi

MORE INFORMATION

       For more information, please see the official MPI Forum web site, which contains the  text
       of both the MPI-1 and MPI-2 standards.  These documents contain detailed information about
       each MPI function (most of which is not duplicated in these man pages).

       http://www.mpi-forum.org/

ACKNOWLEDGEMENTS

       The LAM Team would like the thank the MPICH Team for the handy  program  to  generate  man
       pages   ("doctext"  from  ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz  ),  the  initial
       formatting, and some initial text for most of the MPI-1 man pages.

LOCATION

       initthr.c