DTPCON (3) Linux Manual Page

dtpcon.f –

Synopsis

Functions/Subroutines

subroutine dtpcon (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

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