# ssvdct.f - Man Page

TESTING/EIG/ssvdct.f

## Synopsis

### Functions/Subroutines

subroutine **ssvdct** (n, s, e, shift, num)**SSVDCT**

## Function/Subroutine Documentation

### subroutine ssvdct (integer n, real, dimension( * ) s, real, dimension( * ) e, real shift, integer num)

**SSVDCT**

**Purpose:**

SSVDCT counts the number NUM of eigenvalues of a 2*N by 2*N tridiagonal matrix T which are less than or equal to SHIFT. T is formed by putting zeros on the diagonal and making the off-diagonals equal to S(1), E(1), S(2), E(2), ... , E(N-1), S(N). If SHIFT is positive, NUM is equal to N plus the number of singular values of a bidiagonal matrix B less than or equal to SHIFT. Here B has diagonal entries S(1), ..., S(N) and superdiagonal entries E(1), ... E(N-1). If SHIFT is negative, NUM is equal to the number of singular values of B greater than or equal to -SHIFT. 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 bidiagonal matrix B.

*S*S is REAL array, dimension (N) The diagonal entries of the bidiagonal matrix B.

*E*E is REAL array of dimension (N-1) The superdiagonal entries of the bidiagonal matrix B.

*SHIFT*SHIFT is REAL 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 **86** of file **ssvdct.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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

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