MPIWincreate

MPIWincreate, more commonly referred to as MPI_Win_create, is a collective routine in the MPI standard that creates an MPI window object for one-sided communication. It associates a memory region on each process of a given communicator with a window that can be accessed by other processes using RMA operations such as MPI_Put, MPI_Get, and MPI_Accumulate. The created window enables different synchronization models, including active-target and passive-target approaches, depending on subsequent synchronization calls.

The function signature (in C) is typically int MPI_Win_create(void *base, MPI_Aint size, int disp_unit, const MPI_Info info, MPI_Comm comm, MPI_Win *win). In Fortran, it is called with the corresponding arguments. The parameters are: base, a pointer to the memory region to expose; size, the size of that region in bytes; disp_unit, the unit for displacements in RMA operations; info, an info object (MPI_INFO_NULL is common); comm, a communicator that groups the processes participating in the window; and win, the output window object. All processes in the communicator must call MPI_Win_create with the same size and disp_unit, though the actual memory at base may differ per process. If size is zero, an empty window is created; base may be MPI_BOTTOM on processes that do not contribute memory.

The resulting window object is used in subsequent RMA operations and in synchronization routines. When finished, MPI_Win_free releases the resources associated with the window. MPI_Win_create is a foundational routine for one-sided communication in MPI.