PCShellSetApplyRichardson

Sets routine to use as preconditioner in Richardson iteration.

#include "petscpc.h" 
int PCShellSetApplyRichardson(PC pc,int (*apply)(void*,Vec,Vec,Vec,PetscReal,PetscReal,PetscReal,int),void *ptr)

Collective on PC

	pc	- the preconditioner context
	apply	- the application-provided preconditioning routine
	ptr	- pointer to data needed by this routine

   int apply (void *ptr,Vec b,Vec x,Vec r,PetscReal rtol,PetscReal atol,PetscReal dtol,int maxits)

	ptr	- the application context
	b	- right-hand-side
	x	- current iterate
	r	- work space
	rtol	- relative tolerance of residual norm to stop at
	atol	- absolute tolerance of residual norm to stop at
	dtol	- if residual norm increases by this factor than return
	maxits	- number of iterations to run

PC, shell, set, apply, Richardson, user-provided