?larrc

Computes the number of eigenvalues of the symmetric tridiagonal matrix.

Syntax

call slarrc( jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt, info )

call dlarrc( jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt, info )

Include Files

The FORTRAN 77 interfaces are specified in the mkl_lapack.fi include file (to be used in Fortran programs) and in the mkl_lapack.h include file (to be used in C programs).

Description

The routine finds the number of eigenvalues of the symmetric tridiagonal matrix T or of its factorization L*D*L^T in the specified interval.

Input Parameters

jobt

CHARACTER*1.

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

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

n

INTEGER.

The order of the matrix. (n > 1).

vl,vu

REAL for slarrc

DOUBLE PRECISION for dlarrc

The lower and upper bounds for the eigenvalues.

d

REAL for slarrc

DOUBLE PRECISION for dlarrc

Array, DIMENSION (n).

If jobt= 'T': contains the n diagonal elements of the tridiagonal matrix T.

If jobt= 'L': contains the n diagonal elements of the diagonal matrix D.

e

REAL for slarrc

DOUBLE PRECISION for dlarrc

Array, DIMENSION (n).

If jobt= 'T': contains the (n-1)offdiagonal elements of the matrix T.

If jobt= 'L': contains the (n-1)offdiagonal elements of the matrix L.

pivmin

REAL for slarrc

DOUBLE PRECISION for dlarrc

The minimum pivot in the Sturm sequence for the matrix T.

Output Parameters

eigcnt

INTEGER.

The number of eigenvalues of the symmetric tridiagonal matrix T that are in the half-open interval (vl,vu].

lcnt,rcnt

INTEGER.

The left and right negcounts of the interval.

info

INTEGER.

Now it is not used and always is set to 0.