Allocate memory for message passing and RMA


int MPI_Alloc_mem(MPI_Aint size, MPI_Info info, void *baseptr)

Input Parameters

size of memory segment in bytes (nonnegative integer)
info argument (handle)

Output Parameters

pointer to beginning of memory segment allocated


Using this routine from Fortran requires that the Fortran compiler accept a common pointer extension. See Section 4.11 (Memory Allocation) in the MPI-2 standard for more information and examples.

Also note that while baseptr is a void * type, this is simply to allow easy use of any pointer object for this parameter. In fact, this argument is really a void ** type, that is, a pointer to a pointer.

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 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.


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.

No error; MPI routine completed successfully.
Invalid Info
Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).
Insufficient memory available for allocation by MPI_Alloc_mem