MPI-2 windows

All one-sided communications take place in a region of memory defined by an MPI_Window object.

Window object is collectively defined with respect to a base address by:

MPI_Win_create(baseaddr,size,disp_unit,info,comm,win)

MPI_Get/Put/Accumulate operate on window.

MPI_Win_fence(assertion,window) synchronizes RMA ops on window.