HP MLIB User's Guide Vol. 2 7th Ed.

1030 HP MLIB User’s Guide
DSEVES Eigenextraction
Name DSEVES
Eigenextraction
Purpose This subprogram computes selected eigenvalues and eigenvectors of a sparse
symmetric matrix A or of a sparse symmetric matrix pencil (A,B). The matrix or
matrices have already been processed through the structure input, reordering,
and value input phases. This is the standard interface; subroutine DSEVEX
provides additional control parameters.
Usage VECLIB:
CHARACTER*1 which, pbtype
INTEGER*4 neigvl, nfound, ndiscd, ier, warnng
LOGICAL*4 lfinit, rfinit
REAL*8 lftend, rhtend, center, global(150)
CALL DSEVES(neigvl, which, pbtype, lfinit, lftend, rfinit, rhtend, center,
nfound, ndiscd, global, ier, warnng)
VECLIB8:
CHARACTER*1 which, pbtype
INTEGER*8 neigvl, nfound, ndiscd, ier, warnng
LOGICAL*4 lfinit, rfinit
REAL*8 lftend, rhtend, center, global(150)
CALL DSEVES(neigvl, which, pbtype, lfinit, lftend, rfinit, rhtend, center,
nfound, ndiscd, global, ier, warnng)
Input neigvl Number of eigenvalues to be found, neigvl > 0.
which Character string indicating which eigenvalues are to be
computed.
’L’ or ’l’ The lowest (smallest magnitude)
eigenvalues.
’H’ or ’h’ The highest (greatest magnitude)
eigenvalues.
’C’ or ’c’ or
’N’ or ’n’ The eigenvalues nearest center.
’A’ or ’a’ All eigenvalues in the specified
interval.
pbtype Character string indicating type of problem.
’V’ or ’v’ Generalized symmetric (vibration)
problem Kx = λMx, with M positive
semi-definite.