petsc-3.7.1 2016-05-15

KSPInitialResidual

Computes the residual. Either b - A*C*u = b - A*x with right preconditioning or C*(b - A*x) with left preconditioning; that later residual is often called the "preconditioned residual".

Synopsis

#include "petscksp.h" 
PetscErrorCode  KSPInitialResidual(KSP ksp,Vec vsoln,Vec vt1,Vec vt2,Vec vres,Vec vb)

Collective on KSP Many br

Input Parameters

	vsoln	- solution to use in computing residual Many br
	vt1, vt2	- temporary work vectors Many br
	vb	- right-hand-side vector Many br

Output Parameters

vres -calculated residual Many br

Notes

This routine assumes that an iterative method, designed for Many br

    A x = b

will be used with a preconditioner, C, such that the actual problem is either Many br

    AC u = b (right preconditioning) or

    CA x = Cb (left preconditioning).

This means that the calculated residual will be scaled and/or preconditioned; Many brthe true residual Many br

    b-Ax

is returned in the vt2 temporary. Many br

Many br

Keywords