SVDSetDimensions#

Sets the number of singular values to compute and the dimension of the subspace.

Synopsis#

#include "slepcsvd.h" 
PetscErrorCode SVDSetDimensions(SVD svd,PetscInt nsv,PetscInt ncv,PetscInt mpd)

Logically Collective

Input Parameters#

  • svd - the singular value solver context

  • nsv - number of singular values to compute

  • ncv - the maximum dimension of the subspace to be used by the solver

  • mpd - the maximum dimension allowed for the projected problem

Options Database Keys#

  • -svd_nsv <nsv> - sets the number of singular values

  • -svd_ncv <ncv> - sets the dimension of the subspace

  • -svd_mpd <mpd> - sets the maximum projected dimension

Notes#

Use PETSC_DETERMINE for ncv and mpd to assign a reasonably good value, which is dependent on the solution method and the number of singular values required. For any of the arguments, use PETSC_CURRENT to preserve the current value.

The parameters ncv and mpd are intimately related, so that the user is advised to set one of them at most. Normal usage is:

  1. In cases where nsv is small, the user sets ncv (a reasonable default is 2*nsv).

  2. In cases where nsv is large, the user sets mpd.

The value of ncv should always be between nsv and (nsv+mpd), typically ncv=nsv+mpd. If nsv is not too large, mpd=nsv is a reasonable choice, otherwise a smaller value should be used.

See Also#

SVD: Singular Value Decomposition, SVDGetDimensions()

Level#

intermediate

Location#

src/svd/interface/svdopts.c

Examples#

src/svd/tutorials/ex51.c
src/svd/tutorials/ex8.c

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