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MPI_Compare_and_swap - Perform RMA compare-and-swap
#include <mpi.h>
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)
INCLUDE ’mpif.h’
MPI_COMPARE_AND_SWAP(ORIGIN_ADDR, COMPARE_ADDR, RESULT_ADDR, DATATYPE,
TARGET_RANK,
TARGET_DISP, WIN, IERROR)
<type> ORIGIN_ADDR, COMPARE_ADDR, RESULT_ADDR(*)
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
INTEGER DATATYPE, TARGET_RANK, WIN, IERROR
- origin_addr
- Initial address of buffer (choice).
- compare_addr
- Initial address of compare buffer (choice).
- result_addr
- Initial address
of result buffer (choice).
- datatype
- Data type 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
(nonnegative integer).
- win
- Window object (handle).
- IERROR
- Fortran only: Error status (integer).
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.
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 MPI-3 § 5.9.2 on page 176.
The origin and result
buffers (origin_addr and result_addr) must be disjoint.
The
MPI standard prescribes portable Fortran syntax for the TARGET_DISP argument
only for Fortran 90. FORTRAN 77 users may use the non-portable syntax
INTEGER*MPI_ADDRESS_KIND TARGET_DISP
where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the length
of the declared integer in bytes.
It is the user’s responsibility to
guarantee that, when using the accumulate functions, the target displacement
argument is such that accesses to the window are properly aligned according
to the data type arguments in the call to the MPI_Compare_and_swap function.
Almost all MPI routines return an error value; C routines as the
value of the function and Fortran routines in the last argument.
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.
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