dstt22.f - Man Page

TESTING/EIG/dstt22.f

Synopsis

Functions/Subroutines

subroutine dstt22 (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork, result)
DSTT22

Function/Subroutine Documentation

subroutine dstt22 (integer n, integer m, integer kband, double precision, dimension( * ) ad, double precision, dimension( * ) ae, double precision, dimension( * ) sd, double precision, dimension( * ) se, double precision, dimension( ldu, * ) u, integer ldu, double precision, dimension( ldwork, * ) work, integer ldwork, double precision, dimension( 2 ) result)

DSTT22

Purpose:

``` DSTT22  checks a set of M eigenvalues and eigenvectors,

A U = U S

where A is symmetric tridiagonal, the columns of U are orthogonal,
and S is diagonal (if KBAND=0) or symmetric tridiagonal (if KBAND=1).
Two tests are performed:

RESULT(1) = | U' A U - S | / ( |A| m ulp )

RESULT(2) = | I - U'U | / ( m ulp )```
Parameters

N

```          N is INTEGER
The size of the matrix.  If it is zero, DSTT22 does nothing.
It must be at least zero.```

M

```          M is INTEGER
The number of eigenpairs to check.  If it is zero, DSTT22
does nothing.  It must be at least zero.```

KBAND

```          KBAND is INTEGER
The bandwidth of the matrix S.  It may only be zero or one.
If zero, then S is diagonal, and SE is not referenced.  If
one, then S is symmetric tri-diagonal.```

```          AD is DOUBLE PRECISION array, dimension (N)
The diagonal of the original (unfactored) matrix A.  A is
assumed to be symmetric tridiagonal.```

AE

```          AE is DOUBLE PRECISION array, dimension (N)
The off-diagonal of the original (unfactored) matrix A.  A
is assumed to be symmetric tridiagonal.  AE(1) is ignored,
AE(2) is the (1,2) and (2,1) element, etc.```

SD

```          SD is DOUBLE PRECISION array, dimension (N)
The diagonal of the (symmetric tri-) diagonal matrix S.```

SE

```          SE is DOUBLE PRECISION array, dimension (N)
The off-diagonal of the (symmetric tri-) diagonal matrix S.
Not referenced if KBSND=0.  If KBAND=1, then AE(1) is
ignored, SE(2) is the (1,2) and (2,1) element, etc.```

U

```          U is DOUBLE PRECISION array, dimension (LDU, N)
The orthogonal matrix in the decomposition.```

LDU

```          LDU is INTEGER
The leading dimension of U.  LDU must be at least N.```

WORK

`          WORK is DOUBLE PRECISION array, dimension (LDWORK, M+1)`

LDWORK

```          LDWORK is INTEGER
The leading dimension of WORK.  LDWORK must be at least
max(1,M).```

RESULT

```          RESULT is DOUBLE PRECISION array, dimension (2)
The values computed by the two tests described above.  The
values are currently limited to 1/ulp, to avoid overflow.```
Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 137 of file dstt22.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

The man page dstt22(3) is an alias of dstt22.f(3).

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