# dtpcon.f man page

dtpcon.f —

## Synopsis

### Functions/Subroutines

subroutinedtpcon(NORM, UPLO, DIAG, N, AP, RCOND, WORK, IWORK, INFO)DTPCON

## Function/Subroutine Documentation

### subroutine dtpcon (characterNORM, characterUPLO, characterDIAG, integerN, double precision, dimension( * )AP, double precisionRCOND, double precision, dimension( * )WORK, integer, dimension( * )IWORK, integerINFO)

**DTPCON**

**Purpose:**

```
DTPCON estimates the reciprocal of the condition number of a packed
triangular matrix A, in either the 1-norm or the infinity-norm.
The norm of A is computed and an estimate is obtained for
norm(inv(A)), then 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.
```

*UPLO*

```
UPLO is CHARACTER*1
= 'U': A is upper triangular;
= 'L': A is lower triangular.
```

*DIAG*

```
DIAG is CHARACTER*1
= 'N': A is non-unit triangular;
= 'U': A is unit triangular.
```

*N*

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

*AP*

```
AP is DOUBLE PRECISION array, dimension (N*(N+1)/2)
The upper or lower triangular matrix A, packed columnwise in
a linear array. The j-th column of A is stored in the array
AP as follows:
if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
If DIAG = 'U', the diagonal elements of A are not referenced
and are assumed to be 1.
```

*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 (3*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 130 of file dtpcon.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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