MPI_Win_start(3) MPI MPI_Win_start(3) NAME MPI_Win_start - Start an RMA access epoch for MPI SYNOPSIS int MPI_Win_start(MPI_Group group, int assert, MPI_Win win) INPUT PARAMETERS group - group of target processes (handle) assert - program assertion (integer) win - window object (handle) NOTES The assert argument is used to indicate special conditions for the fence that an implementation may use to optimize the MPI_Win_start operation. The value zero is always correct. Other assertion values may be or'ed to- gether. Assertions that are valid for MPI_Win_start are: MPI_MODE_NOCHECK - the matching calls to MPI_WIN_POST have already completed on all target processes when the call to MPI_WIN_START is made. The nocheck option can be specified in a start call if and only if it is specified in each matching post call. This is similar to the opti- mization of ready-send that may save a handshake when the handshake is implicit in the code. (However, ready-send is matched by a regu- lar receive, whereas both start and post must specify the nocheck option.) THREAD AND INTERRUPT SAFETY This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. NOTES FOR FORTRAN All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the end of the argument list. ierr is an inte- ger and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call state- ment. All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran. 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 ar- gument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error han- dler 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 guarantee 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_GROUP - Null or invalid group passed to function. MPI_ERR_WIN - Invalid MPI window object MPI_ERR_OTHER - Other error; use MPI_Error_string to get more information about this error code. 4/10/2026 MPI_Win_start(3)
NAME | SYNOPSIS | INPUT PARAMETERS | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS
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