petsc-3.11.4 2019-09-28
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KSPLSQRGetNorms

 Get norm estimates that LSQR computes internally during KSPSolve().

Synopsis

#include "petscksp.h" 
PetscErrorCode  KSPLSQRGetNorms(KSP ksp,PetscReal *arnorm, PetscReal *anorm)
Not Collective

Input Parameters

ksp -iterative context

Output Parameters

arnorm - good estimate of norm((A*inv(Pmat))'*r), where r = A*x - b, used in specific stopping criterion
anorm - poor estimate of norm(A*inv(Pmat),'fro') used in specific stopping criterion

Notes

Output parameters are meaningful only after KSPSolve(). These are the same quantities as normar and norma in MATLAB's lsqr(), whose output lsvec is a vector of normar / norma for all iterations. If -ksp_lsqr_exact_mat_norm is set or KSPLSQRSetExactMatNorm(ksp, PETSC_TRUE) called, then anorm is exact Frobenius norm.

Keywords

KSP, KSPLSQR

See Also

KSPSolve(), KSPLSQR, KSPLSQRSetExactMatNorm()

Level

intermediate

Location

src/ksp/ksp/impls/lsqr/lsqr.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages