slepc-3.21.1 2024-04-26
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Compute vectors associated to the dense system such as eigenvectors.


#include "slepcds.h" 
PetscErrorCode DSVectors(DS ds,DSMatType mat,PetscInt *j,PetscReal *rnorm)
Logically Collective

Input Parameters

ds  - the direct solver context
mat  - the matrix, used to indicate which vectors are required

Input/Output Parameter

j  - (optional) index of vector to be computed

Output Parameter

rnorm  - (optional) computed residual norm


Allowed values for mat are DS_MAT_X, DS_MAT_Y, DS_MAT_U and DS_MAT_V, to compute right or left eigenvectors, or left or right singular vectors, respectively.

If NULL is passed in argument j then all vectors are computed, otherwise j indicates which vector must be computed. In real non-symmetric problems, on exit the index j will be incremented when a complex conjugate pair is found.

This function can be invoked after the dense problem has been solved, to get the residual norm estimate of the associated Ritz pair. In that case, the relevant information is returned in rnorm.

For computing eigenvectors, LAPACK's _trevc is used so the matrix must be in (quasi-)triangular form, or call DSSolve() first.

See Also






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