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MPI_Win_lock(3OpenMPI)                                                                MPI_Win_lock(3OpenMPI)



NAME
       MPI_Win_lock - Starts an RMA access epoch locking access to a particular rank.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Win_lock(int lock_type, int rank, int assert, MPI_Win win)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_WIN_LOCK(LOCK_TYPE, RANK, ASSERT, WIN, IERROR)
            INTEGER LOCK_TYPE, RANK, ASSERT, WIN, IERROR


C++ Syntax
       #include <mpi.h>
       void MPI::Win::Lock(int lock_type, int rank, int assert) const


INPUT PARAMETERS
       lock_type Either MPI_LOCK_EXCLUSIVE or MPI_LOCK_SHARED (state).

       rank      Rank of locked window (nonnegative integer).

       assert    Program assertion (integer).

       win       Window object (handle).


OUTPUT PARAMETER
       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       Starts  an  RMA access epoch. Locks ensure that only the windows created by specific processes can be
       accessed by those processes (and by no other processes) during that epoch.

       Locks are used to protect accesses to the locked target window effected by RMA calls  issued  between
       the  lock and unlock call, and to protect local load/store accesses to a locked local window executed
       between the lock and unlock call.  Accesses that are protected by an exclusive lock will not be  con-current concurrent
       current  at  the window site with other accesses to the same window that are lock protected. Accesses
       that are protected by a shared lock will not be concurrent at the window site with accesses protected
       by an exclusive lock to the same window.

       The  assert  argument  is  used to provide assertions on the context of the call that may be used for
       various optimizations. (See Section 6.4.4 of the MPI-2 Standard.) A value of assert  =  0  is  always
       valid.


NOTES
       In a client/server environment in which clients connect to a server and create windows that span both
       the client and the server, if a client or server that has obtained a lock on such a window  and  then
       terminates abnormally, the server or other clients may hang in a MPI_Win_lock call, failing to notice
       that the peer MPI job has terminated.


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++ functions 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_Win_unlock




Open MPI 1.2                                     March 2007                           MPI_Win_lock(3OpenMPI)