---
name: "MPI_Win_create_c"
section: "3"
platform: "linux"
package: "mpich-doc"
version: "4.0.2-3"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Win_create_c"
---

# MPI\_Win\_create\_c(3)

Create an MPI Window object for one-sided communication

## NAME

MPI\_Win\_create\_c -  Create an MPI Window object for one-sided communication

## SYNOPSIS

```
int MPI_Win_create_c(void *base, MPI_Aint size, MPI_Aint disp_unit, MPI_Info info, MPI_Comm comm,
MPI_Win *win)
```

## INPUT PARAMETERS

- **base**

  \- initial address of window (choice) (choice)

- **size**

  \- size of window in bytes (non-negative integer) (non-negative integer)

- **disp\_unit**

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

- **info**

  \- info argument (handle) (handle)

- **comm**

  \- intra-communicator (handle) (handle)

## OUTPUT PARAMETERS

- **win**

  \- window object (handle) (handle)

## NOTES

The displacement unit argument is provided to facilitate address arithmetic in RMA operations: the target displacement argument of an RMA operation is scaled by the factor disp\_unit specified by the target process, at window creation.

The info argument provides optimization hints to the runtime about the expected usage pattern of the window. The following info keys are predefined.

- **no\_locks**

  \- If set to true, then the implementation may assume that passive target synchronization (i.e.,  *MPI\_Win\_lock* ,  *MPI\_Win\_lock\_all* ) will not be used on the given window. This implies that this window is not used for 3-party communication, and RMA can be implemented with no (less) asynchronous agent activity at this process.

- **accumulate\_ordering**

  \- Controls the ordering of accumulate operations at the target.  The argument string should contain a comma-separated list of the following read/write ordering rules, where e.g. "raw" means read-after-write: "rar,raw,war,waw".

- **accumulate\_ops**

  \- If set to same\_op, the implementation will assume that all concurrent accumulate calls to the same target address will use the same operation. If set to same\_op\_no\_op, then the implementation will assume that all concurrent accumulate calls to the same target address will use the same operation or  *MPI\_NO\_OP* . This can eliminate the need to protect access for certain operation types where the hardware can guarantee atomicity. The default is same\_op\_no\_op.

## 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** guarantee 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\_ARG**

  \- Invalid argument.  Some argument is invalid and is not identified by a specific error class (e.g.,  *MPI\_ERR\_RANK* ).

- **MPI\_ERR\_COMM**

  \- Invalid communicator.  A common error is to use a null communicator in a call (not even allowed in  *MPI\_Comm\_rank* ).

- **MPI\_ERR\_DISP**

  \-

- **MPI\_ERR\_INFO**

  \- Invalid Info

- **MPI\_ERR\_SIZE**

  \-

- **MPI\_ERR\_OTHER**

  \- Other error; use  *MPI\_Error\_string* to get more information about this error code.

## SEE ALSO

MPI\_Win\_allocate MPI\_Win\_allocate\_shared MPI\_Win\_create\_dynamic MPI\_Win\_free\