dlarrc-f(3)

dlarrc.f –

Synopsis

Functions/Subroutines

subroutine dlarrc (JOBT, N, VL, VU, D, E, PIVMIN, EIGCNT, LCNT, RCNT, INFO)
DLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix.

Function/Subroutine Documentation

subroutine dlarrc (characterJOBT, integerN, double precisionVL, double precisionVU, double precision, dimension( * )D, double precision, dimension( * )E, double precisionPIVMIN, integerEIGCNT, integerLCNT, integerRCNT, integerINFO)

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

 VU is DOUBLE PRECISION
 The lower and upper bounds 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.

Date:

September 2012

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

Definition at line 136 of file dlarrc.f.

Author

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