# dtpcon.f man page

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.

**Date:**December 2016

Definition at line 132 of file dtpcon.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dtpcon(3) is an alias of dtpcon.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK