SVDComputeError#

Computes the error (based on the residual norm) associated with the i-th singular triplet.

Synopsis#

#include "slepcsvd.h" 
PetscErrorCode SVDComputeError(SVD svd,PetscInt i,SVDErrorType type,PetscReal *error)

Collective

Input Parameters#

  • svd - the singular value solver context

  • i - the solution index

  • type - the type of error to compute

Output Parameter#

  • error - the error

Notes#

The error can be computed in various ways, all of them based on the residual norm obtained as sqrt(n1^2+n2^2) with n1 = ||Av-sigmau||_2 and n2 = ||A^Tu-sigmav||_2, where sigma is the singular value, u is the left singular vector and v is the right singular vector.

In the case of the GSVD, the two components of the residual norm are n1 = ||s^2A’u-cB’Bx||_2 and n2 = ||c^2B’v-sA’Ax||_2, where [u;v] are the left singular vectors and x is the right singular vector, with sigma=c/s.

See Also#

SVDErrorType, SVDSolve()

Level#

beginner

Location#

src/svd/interface/svdsolve.c

Examples#

src/svd/tutorials/ex15f.F90
src/svd/tutorials/ex45.c
src/svd/tutorials/ex15.c

Index of all SVD routines Table of Contents for all manual pages Index of all manual pages