VecScatterCreate

Creates a vector scatter context.

Synopsis

#include "petscvec.h" 
int VecScatterCreate(Vec xin,IS ix,Vec yin,IS iy,VecScatter *newctx)

Collective on Vec

Input Parameters

	xin	- a vector that defines the shape (parallel data layout of the vector) of vectors from which we scatter
	yin	- a vector that defines the shape (parallel data layout of the vector) of vectors to which we scatter
	ix	- the indices of xin to scatter
	iy	- the indices of yin to hold results

Output Parameter

newctx -location to store the new scatter context

Options Database Keys

	-vecscatter_merge	- Merges scatter send and receive (may offer better performance with some MPIs)
	-vecscatter_ssend	- Uses MPI_Ssend_init() instead of MPI_Send_init() (may offer better performance with some MPIs)
	-vecscatter_sendfirst	- Posts sends before receives (may offer better performance with some MPIs)
	-vecscatter_rr	- use ready receiver mode for MPI sends in scatters (rarely used)
	-vecscatter_packtogether	- Pack all messages before sending, receive all messages before unpacking

Notes

In calls to VecScatter() you can use different vectors than the xin and yin you used above; BUT they must have the same parallel data layout, for example, they could be obtained from VecDuplicate(). A VecScatter context CANNOT be used in two or more simultaneous scatters; that is you cannot call a second VecScatterBegin() with the same scatter context until the VecScatterEnd() has been called on the first VecScatterBegin(). In this case a separate VecScatter is needed for each concurrent scatter.

Examples

src/dm/ao/examples/tutorials/ex2.c.html