MPI_Win_create - Specifies an window accessible by remote processes
#include <mpi.h> int MPI_Win_create(void *base, MPI_Aint size, int disp_unit,
MPI_Info info, MPI_Comm comm, MPI_Win *newwin)
Common choices for disp_unit are 1 (no scaling), and (in C syntax) sizeof(type), for a window that consists of an array of elements of type type. The later choice will allow one to use array indices in RMA calls, and have those scaled correctly to byte displacements, even in a heterogeneous environment. ( End of advice to users.) The info argument provides optimization hints to the runtime about the expected usage pattern of the window.
The various processes in the group of comm may specify completely different target windows, in location, size, displacement units and info arguments. As long as all the get, put and accumulate accesses to a particular process fit their specific target window this should pose no problem. The same area in memory may appear in multiple windows, each associated with a different window object. However, concurrent communications to distinct, overlapping windows may lead to erroneous results.
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.
USAGE WITH IMPI EXTENSIONS¶
The IMPI standard only supports MPI-1 functions. Hence, this function is currently not designed to operate within an IMPI job.
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.
- - No error; MPI routine completed successfully.
- - Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank ).
- - 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.
- - Other error; use MPI_Error_string to get more information about this error code.
- - An internal error has been detected. This is fatal. Please send a bug report to the LAM mailing list (see http://www.lam-mpi.org/contact.php ).
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).