DLARRC(3)      LAPACK routine of NEC Numeric Library Collection      DLARRC(3)



NAME
       DLARRC

SYNOPSIS
       SUBROUTINE DLARRC (JOBT, N, VL, VU, D, E, PIVMIN, EIGCNT, LCNT, RCNT,
           INFO)



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'.




ARGUMENTS
           JOBT      (input)
                     JOBT is CHARACTER*1
                     = 'T':  Compute Sturm count for matrix T.
                     = 'L':  Compute Sturm count for matrix L D L^T.

           N         (input)
                     N is INTEGER
                     The order of the matrix. N > 0.

           VL        (input)
                     VL is DOUBLE PRECISION

           VU        (input)
                     VU is DOUBLE PRECISION
                     The lower and upper bounds for the eigenvalues.

           D         (input)
                     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         (input)
                     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    (input)
                     PIVMIN is DOUBLE PRECISION
                     The minimum pivot in the Sturm sequence for T.

           EIGCNT    (output)
                     EIGCNT is INTEGER
                     The number of eigenvalues of the symmetric tridiagonal matrix T
                     that are in the interval (VL,VU]

           LCNT      (output)
                     LCNT is INTEGER

           RCNT      (output)
                     RCNT is INTEGER
                     The left and right negcounts of the interval.

           INFO      (output)
                     INFO is INTEGER



LAPACK routine                  31 October 2017                      DLARRC(3)