NAME

       MPI_Compare_and_swap -  Perform one-sided atomic compare-and-swap.

SYNOPSIS

       int MPI_Compare_and_swap(const void *origin_addr, const void *compare_addr,
               void *result_addr, MPI_Datatype datatype, int target_rank,
               MPI_Aint target_disp, MPI_Win win)

       This function compares one element of type datatype in the compare buffer compare_addr with the buffer at
       offset target_disp in the target window specified by target_rank and win and replaces the  value  at  the
       target  with  the  value in the origin buffer origin_addr if the compare buffer and the target buffer are
       identical. The original value at the target is returned in the buffer result_addr.

INPUT PARAMETERS

       origin_addr
              - initial address of buffer (choice)
       compare_addr
              - initial address of compare buffer (choice)
       result_addr
              - initial address of result buffer (choice)
       datatype
              - datatype of the entry in origin, result, and target buffers (handle)
       target_rank
              - rank of target (nonnegative integer)
       target_disp
              - displacement from start of window to beginning of target buffer (non-negative integer)
       win    - window object (handle)

NOTES

       This operation is atomic with respect to other "accumulate" operations.

       The parameter datatype must belong to one of the following categories of predefined datatypes: C integer,
       Fortran  integer,  Logical,  Multi-language types, or Byte as specified in Section 5.9.2 on page 176. The
       origin and result buffers (origin_addr and result_addr) must be disjoint.

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 integer 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 statement.

       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 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_ARG
              -  Invalid  argument.   Some  argument  is invalid and is not identified by a specific error class
              (e.g., MPI_ERR_RANK ).
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is often valid.
       MPI_ERR_OP
              - Invalid operation.  MPI operations (objects  of  type  MPI_Op  )  must  either  be  one  of  the
              predefined operations (e.g., MPI_SUM ) or created with MPI_Op_create .

       MPI_ERR_RANK
              - Invalid source or destination rank.  Ranks must be between zero and the size of the communicator
              minus one; ranks in a receive  (  MPI_Recv  ,  MPI_Irecv  ,  MPI_Sendrecv  ,  etc.)  may  also  be
              MPI_ANY_SOURCE .

       MPI_ERR_TYPE
              -  Invalid  datatype  argument.  Additionally, this error can occur if an uncommitted MPI_Datatype
              (see MPI_Type_commit ) is used in a communication call.
       MPI_ERR_WIN
              - Invalid MPI window object

                                                   11/12/2016                            MPI_Compare_and_swap(3)