KSPInitialResidual#

Computes the residual. Either b - ACu = b - Ax with right preconditioning or C(b - A*x) with left preconditioning; the latter 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

Input Parameters#

  • vsoln - solution to use in computing residual

  • vt1, vt2 - temporary work vectors

  • vb - right-hand-side vector

Output Parameter#

  • vres - calculated residual

Note#

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

b-Ax

is returned in the vt2 temporary.

See Also#

KSP: Linear System Solvers, KSP, KSPSolve(), KSPMonitor()

Level#

developer

Location#

src/ksp/ksp/interface/itres.c

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Index of all KSP routines
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Index of all manual pages