# dgecon.f man page

dgecon.f —

## Synopsis

### Functions/Subroutines

subroutinedgecon(NORM, N, A, LDA, ANORM, RCOND, WORK, IWORK, INFO)DGECON

## Function/Subroutine Documentation

### subroutine dgecon (characterNORM, integerN, double precision, dimension( lda, * )A, integerLDA, double precisionANORM, double precisionRCOND, double precision, dimension( * )WORK, integer, dimension( * )IWORK, integerINFO)

**DGECON**

**Purpose:**

```
DGECON estimates the reciprocal of the condition number of a general
real matrix A, in either the 1-norm or the infinity-norm, using
the LU factorization computed by DGETRF.
An estimate is obtained for norm(inv(A)), and the reciprocal of the
condition number is computed as
RCOND = 1 / ( norm(A) * norm(inv(A)) ).
```

**Parameters:**

*NORM*

```
NORM is CHARACTER*1
Specifies whether the 1-norm condition number or the
infinity-norm condition number is required:
= '1' or 'O': 1-norm;
= 'I': Infinity-norm.
```

*N*

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

*A*

```
A is DOUBLE PRECISION array, dimension (LDA,N)
The factors L and U from the factorization A = P*L*U
as computed by DGETRF.
```

*LDA*

```
LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,N).
```

*ANORM*

```
ANORM is DOUBLE PRECISION
If NORM = '1' or 'O', the 1-norm of the original matrix A.
If NORM = 'I', the infinity-norm of the original matrix A.
```

*RCOND*

```
RCOND is DOUBLE PRECISION
The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(norm(A) * norm(inv(A))).
```

*WORK*

`WORK is DOUBLE PRECISION array, dimension (4*N)`

*IWORK*

`IWORK is INTEGER array, dimension (N)`

*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.

**Date:**

November 2011

Definition at line 124 of file dgecon.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dgecon(3) is an alias of dgecon.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK