17.2.13. MPI_Alloc_mem

MPI_Alloc_mem - Allocates a specified memory segment.

17.2.13.1. SYNTAX

17.2.13.1.1. C Syntax

#include <mpi.h>

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

17.2.13.1.2. Fortran Syntax (see FORTRAN NOTES)

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_ALLOC_MEM(SIZE, INFO, BASEPTR, IERROR)
     INTEGER INFO, IERROR
     INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR

17.2.13.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Alloc_mem(size, info, baseptr, ierror)
     USE, INTRINSIC :: ISO_C_BINDING, ONLY
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: size
     TYPE(MPI_Info), INTENT(IN) :: info
     TYPE(C_PTR), INTENT(OUT) :: baseptr
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.13.2. INPUT PARAMETERS

  • size: Size of memory segment in bytes (nonnegative integer).

  • info: Info argument (handle).

17.2.13.3. OUTPUT PARAMETERS

  • baseptr: Pointer to beginning of memory segment allocated.

  • IERROR: Fortran only: Error status (integer).

17.2.13.4. DESCRIPTION

MPI_Alloc_mem allocates size bytes of memory. The starting address of this memory is returned in the variable baseptr.

17.2.13.5. C NOTES

The parameter baseptr is of type void * to allow passing any pointer object for this parameter. The provided argument should be a pointer to a pointer of arbitrary type (e.g., void **).

17.2.13.6. FORTRAN NOTES

There is no portable FORTRAN 77 syntax for using MPI_Alloc_mem. There is no portable Fortran syntax for using pointers returned from MPI_Alloc_mem. However, MPI_Alloc_mem can be used with Sun Fortran compilers.

From FORTRAN 77, you can use the following non-standard declarations for the SIZE and BASEPTR arguments:

INCLUDE "mpif.h"
INTEGER*MPI_ADDRESS_KIND SIZE, BASEPTR

From either FORTRAN 77 or Fortran 90, you can use “Cray pointers” for the BASEPTR argument. Cray pointers are described further in the Fortran User’s Guide and are supported by many Fortran compilers. For example,

INCLUDE "mpif.h"
REAL*4 A(100,100)
POINTER (BASEPTR, A)
INTEGER*MPI_ADDRESS_KIND SIZE

SIZE = 4 * 100 * 100
CALL MPI_ALLOC_MEM(SIZE,MPI_INFO_NULL,BASEPTR,IERR)

! use A

CALL MPI_FREE_MEM(A, IERR)

17.2.13.7. ERRORS

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_INIT / MPI_INIT_THREAD, after MPI_FINALIZE, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_COMM_SET_ERRHANDLER on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_COMM_SPAWN[_MULTIPLE]. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

In the sessions model, the error handler can be set during MPI_Session_init.

Open MPI includes three predefined error handlers that can be used:

MPI_ERRORS_ARE_FATAL: Causes the program to abort all connected MPI processes.
MPI_ERRORS_ABORT:     An error handler that can be invoked on a communicator,
                      window, file, or session. When called on a communicator, it
                      acts as if MPI_ABORT was called on that communicator. If
                      called on a window or file, acts as if MPI_ABORT was called
                      on a communicator containing the group of processes in the
                      corresponding window or file. If called on a session,
                      aborts only the local process.
MPI_ERRORS_RETURN:    Returns an error code to the application.

MPI applications can also implement their own error handlers.

Custom MPI error handlers can be created by calling: MPI_Comm_create_errhandler(3) MPI_File_create_errhandler(3) MPI_Session_create_errhandler(3) MPI_Win_create_errhandler(3)

Predefined and custom error handlers can be set by calling: MPI_Comm_set_errhandler(3) MPI_File_set_errhandler(3) MPI_Session_set_errhandler(3) MPI_Win_set_errhandler(3)

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3 standard for more information.

See also

MPI_Free_mem