---
name: "sdisna.f"
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/sdisna.f"
---

# sdisna.f(3)

## NAME

SRC/sdisna.f

## SYNOPSIS

### Functions/Subroutines

subroutine **sdisna** (job, m, n, d, sep, info)\
 **SDISNA**

## Function/Subroutine Documentation

### subroutine sdisna (character job, integer m, integer n, real, dimension( \* ) d, real, dimension( \* ) sep, integer info)

**SDISNA**

**Purpose:**

```
!>
!> SDISNA computes the reciprocal condition numbers for the eigenvectors
!> of a real symmetric or complex Hermitian matrix or for the left or
!> right singular vectors of a general m-by-n matrix. The reciprocal
!> condition number is the 'gap' between the corresponding eigenvalue or
!> singular value and the nearest other one.
!>
!> The bound on the error, measured by angle in radians, in the I-th
!> computed vector is given by
!>
!>        SLAMCH( 'E' ) * ( ANORM / SEP( I ) )
!>
!> where ANORM = 2-norm(A) = max( abs( D(j) ) ).  SEP(I) is not allowed
!> to be smaller than SLAMCH( 'E' )*ANORM in order to limit the size of
!> the error bound.
!>
!> SDISNA may also be used to compute error bounds for eigenvectors of
!> the generalized symmetric definite eigenproblem.
!>
```

**Parameters**

*JOB*

```
!>          JOB is CHARACTER*1
!>          Specifies for which problem the reciprocal condition numbers
!>          should be computed:
!>          = 'E':  the eigenvectors of a symmetric/Hermitian matrix;
!>          = 'L':  the left singular vectors of a general matrix;
!>          = 'R':  the right singular vectors of a general matrix.
!>
```

*M*

```
!>          M is INTEGER
!>          The number of rows of the matrix. M >= 0.
!>
```

*N*

```
!>          N is INTEGER
!>          If JOB = 'L' or 'R', the number of columns of the matrix,
!>          in which case N >= 0. Ignored if JOB = 'E'.
!>
```

*D*

```
!>          D is REAL array, dimension (M) if JOB = 'E'
!>                              dimension (min(M,N)) if JOB = 'L' or 'R'
!>          The eigenvalues (if JOB = 'E') or singular values (if JOB =
!>          'L' or 'R') of the matrix, in either increasing or decreasing
!>          order. If singular values, they must be non-negative.
!>
```

*SEP*

```
!>          SEP is REAL array, dimension (M) if JOB = 'E'
!>                               dimension (min(M,N)) if JOB = 'L' or 'R'
!>          The reciprocal condition numbers of the vectors.
!>
```

*INFO*

```
!>          INFO is INTEGER
!>          = 0:  successful exit.
!>          < 0:  if INFO = -i, the i-th argument had an illegal value.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **116** of file **sdisna.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.