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.TH "MPI_ALLOC_MEM" "3" "Feb 06, 2024" "" "Open MPI"
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\fI\%MPI_Alloc_mem\fP — Allocates a specified memory segment.
.SH SYNTAX
.SS C Syntax
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.INDENT 3.5
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.nf
.ft C
#include <mpi.h>

int MPI_Alloc_mem(MPI_Aint size, MPI_Info info, void *baseptr)
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.SS Fortran Syntax
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.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_ALLOC_MEM(SIZE, INFO, BASEPTR, IERROR)
     INTEGER INFO, IERROR
     INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR
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.SS Fortran 2008 Syntax
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.ft C
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
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.SH INPUT PARAMETERS
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.IP \(bu 2
\fBsize\fP: Size of memory segment in bytes (nonnegative integer).
.IP \(bu 2
\fBinfo\fP: Info argument (handle).
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.SH OUTPUT PARAMETERS
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.IP \(bu 2
\fBbaseptr\fP: Pointer to beginning of memory segment allocated.
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\fBierror\fP: Fortran only: Error status (integer).
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.SH DESCRIPTION
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\fI\%MPI_Alloc_mem\fP allocates \fIsize\fP bytes of memory. The starting address of
this memory is returned in the variable \fIbaseptr\fP\&.
.SH C NOTES
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The parameter \fIbaseptr\fP is of type \fBvoid *\fP to allow passing any
pointer object for this parameter. The provided argument should be a
pointer to a pointer of arbitrary type (e.g., \fBvoid **\fP).
.SH FORTRAN NOTES
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The \fI\%MPI_Alloc_mem\fP calls require the use of the \fBiso_c_binding\fP module
for due to the use of \fBTYPE(C_PTR)\fP\&.
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.ft C
use iso_c_binding

type(c_ptr) :: alloc_ptr
integer :: size, ierr
double precision, pointer :: array(:,:)

! A 2D array of 100 elements
size = 10 * 10
call MPI_Alloc_Mem(size * 8, MPI_INFO_NULL, alloc_ptr, ierr)

! Point to the array
call c_f_pointer(alloc_ptr, array, [10, 10])

! ... use the array ...

! Free the memory, no need for the alloc_ptr
call MPI_Free_mem(array, ierr)
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.SH ERRORS
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Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
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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
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
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.
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Open MPI includes three predefined error handlers that can be used:
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\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP 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.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
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MPI applications can also implement their own error handlers by calling:
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.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
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Note that MPI does not guarantee that an MPI program can continue past
an error.
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See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
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See the Error Handling section of the MPI\-3.1 standard for
more information.
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\fBSEE ALSO:\fP
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.IP \(bu 2
\fI\%MPI_Free_mem\fP
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.SH COPYRIGHT
2003-2024, The Open MPI Community
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