SVDTRLanczosSetScale#

Sets the scale parameter for the GSVD.

Synopsis#

#include "slepcsvd.h" 
PetscErrorCode SVDTRLanczosSetScale(SVD svd,PetscReal scale)

Logically Collective

Input Parameters#

  • svd - the singular value solver context

  • scale - scale parameter

Options Database Key#

  • -svd_trlanczos_scale <scale> - scale factor/threshold

Notes#

This parameter is relevant for the GSVD case only. If the parameter is positive, it indicates the scale factor to multiply \(B\) in the stacked matrix \(Z=[A^*,B^*]^*\). If negative, its absolute value is the threshold for automatic scaling. In automatic scaling, whenever the largest approximate generalized singular value (or the inverse of the smallest value, if SVD_SMALLEST is used) exceeds the threshold, the computation is restarted with matrix \(B\) scaled by that value.

See Also#

SVD: Singular Value Decomposition, SVDTRLANCZOS, SVDTRLanczosGetScale()

Level#

advanced

Location#

src/svd/impls/trlanczos/trlanczos.c

Examples#

src/svd/tutorials/ex51.c

Implementations#

SVDTRLanczosSetScale_TRLanczos() in src/svd/impls/trlanczos/trlanczos.c

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