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'.

JOBT

          JOBT is CHARACTER*1


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


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

N

          N is INTEGER


          The order of the matrix. N > 0.

VL

          VL is REAL


          The lower bound for the eigenvalues.

VU

          VU is REAL


          The upper bound for the eigenvalues.

D

          D is REAL 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

          E is REAL 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 REAL


          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

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

June 2016

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