LAPACK

NAME¶

larrc - larrc: step in stemr

SYNOPSIS¶

Functions¶

subroutine dlarrc (jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt, info)
DLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix. subroutine slarrc (jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt, info)
SLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix.

Detailed Description¶

Function Documentation¶

subroutine dlarrc (character jobt, integer n, double precision vl, double precision vu, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision pivmin, integer eigcnt, integer lcnt, integer rcnt, integer info)¶

DLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix.

Purpose:



 Find the number of eigenvalues of the symmetric tridiagonal matrix T


 that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T


 if JOBT = 'L'.

Parameters

JOBT



          JOBT is CHARACTER*1


          = 'T':  Compute Sturm count for matrix T.


          = 'L':  Compute Sturm count for matrix L D L^T.



          N is INTEGER


          The order of the matrix. N > 0.



          VL is DOUBLE PRECISION


          The lower bound for the eigenvalues.



          VU is DOUBLE PRECISION


          The upper bound for the eigenvalues.



          D is DOUBLE PRECISION array, dimension (N)


          JOBT = 'T': The N diagonal elements of the tridiagonal matrix T.


          JOBT = 'L': The N diagonal elements of the diagonal matrix D.



          E is DOUBLE PRECISION array, dimension (N)


          JOBT = 'T': The N-1 offdiagonal elements of the matrix T.


          JOBT = 'L': The N-1 offdiagonal elements of the matrix L.

PIVMIN



          PIVMIN is DOUBLE PRECISION


          The minimum pivot in the Sturm sequence for T.

EIGCNT



          EIGCNT is INTEGER


          The number of eigenvalues of the symmetric tridiagonal matrix T


          that are in the interval (VL,VU]

LCNT



          LCNT is INTEGER

RCNT



          RCNT is INTEGER


          The left and right negcounts of the interval.

INFO



          INFO is INTEGER

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

Beresford Parlett, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA

subroutine slarrc (character jobt, integer n, real vl, real vu, real, dimension( * ) d, real, dimension( * ) e, real pivmin, integer eigcnt, integer lcnt, integer rcnt, integer info)¶

SLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix.