.TH MPI_Win_allocate 3 "11/12/2019" " " "MPI"

.SH NAME

MPI_Win_allocate \-  Create and allocate an MPI Window object for one-sided communication. 

.SH SYNOPSIS

.nf

int MPI_Win_allocate(MPI_Aint size, int disp_unit, MPI_Info info,

MPI_Comm comm, void *baseptr, MPI_Win * win)

.fi

This is a collective call executed by all processes in the group of comm. On

each process, it allocates memory of at least size bytes, returns a pointer to

it, and returns a window object that can be used by all processes in comm to

perform RMA operations. The returned memory consists of size bytes local to

each process, starting at address baseptr and is associated with the window as

if the user called 

.I MPI_Win_create

on existing memory. The size argument may be

different at each process and size = 0 is valid; however, a library might

allocate and expose more memory in order to create a fast, globally symmetric

allocation.

.SH INPUT PARAMETERS

.PD 0

.TP

.B size 

- size of window in bytes (nonnegative integer)

.PD 1

.PD 0

.TP

.B disp_unit 

- local unit size for displacements, in bytes (positive integer)

.PD 1

.PD 0

.TP

.B info 

- info argument (handle)

.PD 1

.PD 0

.TP

.B comm 

- communicator (handle)

.PD 1

.SH OUTPUT PARAMETERS

.PD 0

.TP

.B baseptr 

- base address of the window in local memory

.PD 1

.PD 0

.TP

.B win 

- window object returned by the call (handle)

.PD 1

.SH 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 

.I malloc

or other non-MPICH runtime routines that are themselves not interrupt-safe.

.SH NOTES FOR FORTRAN

All MPI routines in Fortran (except for 

.I MPI_WTIME

and 

.I MPI_WTICK

) have

an additional argument 

.I ierr

at the end of the argument list.  

.I 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

.I call

statement.

All MPI objects (e.g., 

.I MPI_Datatype

, 

.I MPI_Comm

) are of type 

.I INTEGER

in Fortran.

.SH ERRORS

All MPI routines (except 

.I MPI_Wtime

and 

.I 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 

.I MPI_Comm_set_errhandler

(for communicators),

.I MPI_File_set_errhandler

(for files), and 

.I MPI_Win_set_errhandler

(for

RMA windows).  The MPI-1 routine 

.I MPI_Errhandler_set

may be used but

its use is deprecated.  The predefined error handler

.I MPI_ERRORS_RETURN

may be used to cause error values to be returned.

Note that MPI does 

.B not

guarentee that an MPI program can continue past

an error; however, MPI implementations will attempt to continue whenever

possible.

.PD 0

.TP

.B MPI_SUCCESS 

- No error; MPI routine completed successfully.

.PD 1

.PD 0

.TP

.B MPI_ERR_ARG 

- Invalid argument.  Some argument is invalid and is not

identified by a specific error class (e.g., 

.I MPI_ERR_RANK

).

.PD 1

.PD 0

.TP

.B MPI_ERR_COMM 

- Invalid communicator.  A common error is to use a null

communicator in a call (not even allowed in 

.I MPI_Comm_rank

).

.PD 1

.PD 0

.TP

.B MPI_ERR_INFO 

- Invalid Info 

.PD 1

.PD 0

.TP

.B MPI_ERR_OTHER 

- Other error; use 

.I MPI_Error_string

to get more information

about this error code. 

.PD 1

.PD 0

.TP

.B MPI_ERR_SIZE 

- 

.PD 1

.SH SEE ALSO

MPI_Win_allocate_shared MPI_Win_create MPI_Win_create_dynamic MPI_Win_free

.br