---
name: "slarrr"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/slarrr.f"
---

# slarrr(3)

Part of [slarrr.f(3)](/slarrr.f/3.md).

## NAME

SRC/slarrr.f

## SYNOPSIS

### Functions/Subroutines

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/Subroutine Documentation

### 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.