# larrr - Man Page

larrr: step in stemr, test to do expensive tridiag eig algorithm

## Synopsis

### Functions

subroutine dlarrr (n, d, e, info)
DLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.
subroutine slarrr (n, d, e, info)
SLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

## Function Documentation

### subroutine dlarrr (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, integer info)

DLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

Purpose:

``` Perform tests to decide whether the symmetric tridiagonal matrix T
warrants expensive computations which guarantee high relative accuracy
in the eigenvalues.```
Parameters

N

```          N is INTEGER
The order of the matrix. N > 0.```

D

```          D is DOUBLE PRECISION array, dimension (N)
The N diagonal elements of the tridiagonal matrix T.```

E

```          E is DOUBLE PRECISION array, dimension (N)
On entry, the first (N-1) entries contain the subdiagonal
elements of the tridiagonal matrix T; E(N) is set to ZERO.```

INFO

```          INFO is INTEGER
INFO = 0(default) : the matrix warrants computations preserving
relative accuracy.
INFO = 1          : the matrix warrants computations guaranteeing
only absolute accuracy.```
Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

Beresford Parlett, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA

Definition at line 93 of file dlarrr.f.

### subroutine slarrr (integer n, real, dimension( * ) d, real, dimension( * ) e, integer info)

SLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

Purpose:

``` Perform tests to decide whether the symmetric tridiagonal matrix T
warrants expensive computations which guarantee high relative accuracy
in the eigenvalues.```
Parameters

N

```          N is INTEGER
The order of the matrix. N > 0.```

D

```          D is REAL array, dimension (N)
The N diagonal elements of the tridiagonal matrix T.```

E

```          E is REAL array, dimension (N)
On entry, the first (N-1) entries contain the subdiagonal
elements of the tridiagonal matrix T; E(N) is set to ZERO.```

INFO

```          INFO is INTEGER
INFO = 0(default) : the matrix warrants computations preserving
relative accuracy.
INFO = 1          : the matrix warrants computations guaranteeing
only absolute accuracy.```
Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

Beresford Parlett, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA

Definition at line 93 of file slarrr.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Info

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK