petsc3.13.6 20200929
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
Input Parameters
 vsoln   solution to use in computing residual

 vt1, vt2   temporary work vectors

 vb   righthandside vector

Output Parameters
vres calculated residual
Notes
This routine assumes that an iterative method, designed for
A x = b
will be used with a preconditioner, C, such that the actual problem is either
AC u = b (right preconditioning) or
CA x = Cb (left preconditioning).
This means that the calculated residual will be scaled and/or preconditioned;
the true residual
bAx
is returned in the vt2 temporary.
See Also
KSPMonitor()
Level
developer
Location
src/ksp/ksp/interface/itres.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages