# dstect.f - Man Page

TESTING/EIG/dstect.f

## Synopsis

### Functions/Subroutines

subroutine **dstect** (n, a, b, shift, num)**DSTECT**

## Function/Subroutine Documentation

### subroutine dstect (integer n, double precision, dimension( * ) a, double precision, dimension( * ) b, double precision shift, integer num)

**DSTECT**

**Purpose:**

DSTECT counts the number NUM of eigenvalues of a tridiagonal matrix T which are less than or equal to SHIFT. T has diagonal entries A(1), ... , A(N), and offdiagonal entries B(1), ..., B(N-1). See W. Kahan 'Accurate Eigenvalues of a Symmetric Tridiagonal Matrix', Report CS41, Computer Science Dept., Stanford University, July 21, 1966

**Parameters***N*N is INTEGER The dimension of the tridiagonal matrix T.

*A*A is DOUBLE PRECISION array, dimension (N) The diagonal entries of the tridiagonal matrix T.

*B*B is DOUBLE PRECISION array, dimension (N-1) The offdiagonal entries of the tridiagonal matrix T.

*SHIFT*SHIFT is DOUBLE PRECISION The shift, used as described under Purpose.

*NUM*NUM is INTEGER The number of eigenvalues of T less than or equal to SHIFT.

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **81** of file **dstect.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dstect(3) is an alias of dstect.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK