# 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