# MPI_Win_create_dynamic

Create an MPI Window object for one-sided communication. This window allows memory to be dynamically exposed and un-exposed for RMA operations.

## Synopsis

    int MPI_Win_create_dynamic(MPI_Info info, MPI_Comm comm, MPI_Win * win)

This is a collective call executed by all processes in the group of comm. It returns a window win without memory attached. Existing process memory can be attached as described below. This routine returns a window object that can be used by these processes to perform RMA operations on attached memory. Because this window has special properties, it will sometimes be referred to as a dynamic window. The info argument can be used to specify hints similar to the info argument for `MPI_Win_create`.

In the case of a window created with `MPI_Win_create_dynamic`, the target_disp for all RMA functions is the address at the target; i.e., the effective window_base is `MPI_BOTTOM` and the disp_unit is one. For dynamic windows, the target_disp argument to RMA communication operations is not restricted to non-negative values. Users should use `MPI_Get_address` at the target process to determine the address of a target memory location and communicate this address to the origin process.

## Input Parameters

info
  info argument (handle)
comm
  communicator (handle)

## Output Parameters

win
  window object returned by the call (handle)

## Notes

Users are cautioned that displacement arithmetic can overflow in variables of type `MPI_Aint` and result in unexpected values on some platforms. This issue may be addressed in a future version of MPI.

Memory in this window may not be used as the target of one-sided accesses in this window until it is attached using the function `MPI_Win_attach`. That is, in addition to using `MPI_Win_create_dynamic` to create an MPI window, the user must use `MPI_Win_attach` before any local memory may be the target of an MPI RMA operation. Only memory that is currently accessible may be attached.

## 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_INFO
  Invalid Info

MPI_ERR_OTHER
  Other error; use `MPI_Error_string` to get more information about this error code.

MPI_ERR_SIZE

## See Also

MPI_Win_attach MPI_Win_detach MPI_Win_allocate MPI_Win_allocate_shared MPI_Win_create MPI_Win_free