# MPI_Alloc_mem

Allocate memory for message passing and RMA

## Synopsis

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

## Input Parameters

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

## Output Parameters

baseptr
  pointer to beginning of memory segment allocated

## Notes

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.

## 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_INFO
  Invalid Info

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_NO_MEM
  Insufficient memory available for allocation by `MPI_Alloc_mem`