---
name: "MPI_Win_shared_query.openmpi"
section: "3"
platform: "linux"
package: "openmpi-doc"
version: "5.0.7-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Win_shared_query.openmpi"
---

# MPI\_Win\_shared\_query.openmpi(3)

*MPI\_Win\_shared\_query* — Query a shared memory window

## SYNTAX

### C Syntax

```
#include <mpi.h>
int MPI_Win_shared_query (MPI_Win win, int rank, MPI_Aint *size,
                          int *disp_unit, void *baseptr)
```

### Fortran Syntax

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_WIN_SHARED_QUERY(WIN, RANK, SIZE, DISP_UNIT, BASEPTR, IERROR)
        INTEGER WIN, RANK, DISP_UNIT, IERROR
        INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR
```

### Fortran 2008 Syntax

```
USE mpi_f08
MPI_Win_shared_query(win, rank, size, disp_unit, baseptr, ierror)
     USE, INTRINSIC :: ISO_C_BINDING, ONLY : C_PTR
     TYPE(MPI_Win), INTENT(IN) :: win
     INTEGER, INTENT(IN) :: rank
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: size
     INTEGER, INTENT(OUT) :: disp_unit
     TYPE(C_PTR), INTENT(OUT) :: baseptr
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

## INPUT PARAMETERS

- •

  **win**: Shared memory window object (handle).

- •

  **rank**: Rank in the group of window *win* (non-negative integer) or **MPI\_PROC\_NULL**.

## OUTPUT PARAMETERS

- •

  **size**: Size of the window segment (non-negative integer).

- •

  **disp\_unit**: Local unit size for displacements, in bytes (positive integer).

- •

  **baseptr**: Address for load/store access to window segment (choice).

- •

  **ierror**: Fortran only: Error status (integer).

## DESCRIPTION

*MPI\_Win\_shared\_query* queries the process-local address for remote memory segments created with *MPI\_Win\_allocate\_shared*. This function can return different process-local addresses for the same physical memory on different processes. The returned memory can be used for load/store accesses subject to the constraints defined in MPI-3.1 section 11.7. This function can only be called with windows of flavor MPI\_WIN\_FLAVOR\_SHARED. If the passed window is not of flavor MPI\_WIN\_FLAVOR\_SHARED, the error MPI\_ERR\_RMA\_FLAVOR is raised. When rank is **MPI\_PROC\_NULL**, the *pointer*, *disp\_unit*, and *size* returned are the pointer, disp\_unit, and size of the memory segment belonging the lowest rank that specified *size* \> 0. If all processes in the group attached to the window specified *size* = 0, then the call returns *size* = 0 and a *baseptr* as if *MPI\_Alloc\_mem* was called with *size* = 0.

## 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 \*\***).

## 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*/*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.

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 by calling:

- •

  *MPI\_Comm\_create\_errhandler* then *MPI\_Comm\_set\_errhandler*

- •

  *MPI\_File\_create\_errhandler* then *MPI\_File\_set\_errhandler*

- •

  *MPI\_Session\_create\_errhandler* then *MPI\_Session\_set\_errhandler* or at *MPI\_Session\_init*

- •

  *MPI\_Win\_create\_errhandler* then *MPI\_Win\_set\_errhandler*

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-3.1 standard for more information.

**SEE ALSO:**

- •

  *MPI\_Alloc\_mem*

- •

  *MPI\_Win\_allocate\_shared*

## COPYRIGHT

2003-2025, The Open MPI Community