---
name: "dtpcon.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/dtpcon.f"
---

# dtpcon.f(3)

## NAME

SRC/dtpcon.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dtpcon** (norm, uplo, diag, n, ap, rcond, work, iwork, info)\
 **DTPCON**

## Function/Subroutine Documentation

### subroutine dtpcon (character norm, character uplo, character diag, integer n, double precision, dimension( \* ) ap, double precision rcond, double precision, dimension( \* ) work, integer, dimension( \* ) iwork, integer info)

**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.

Definition at line **128** of file **dtpcon.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.