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".
PetscErrorCode KSPInitialResidual(KSP ksp,Vec vsoln,Vec vt1,Vec vt2,Vec vres,Vec vb)
Collective on ksp
|vsoln ||- solution to use in computing residual
|vt1, vt2 ||- temporary work vectors
|vb ||- right-hand-side vector
vres -calculated residual
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
is returned in the vt2 temporary.
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages