SPTCON (3) Linux Manual Page

sptcon.f –

Synopsis

Functions/Subroutines

subroutine sptcon (N, D, E, ANORM, RCOND, WORK, INFO)
SPTCON

Function/Subroutine Documentation

subroutine sptcon (integerN, real, dimension( * )D, real, dimension( * )E, realANORM, realRCOND, real, dimension( * )WORK, integerINFO)

SPTCON

Purpose:

 SPTCON computes the reciprocal of the condition number (in the
 1-norm) of a real symmetric positive definite tridiagonal matrix
 using the factorization A = L*D*L**T or A = U**T*D*U computed by
 SPTTRF.
 Norm(inv(A)) is computed by a direct method, and the reciprocal of
 the condition number is computed as
 RCOND = 1 / (ANORM * norm(inv(A))).

 

Parameters:

N

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

D

 D is REAL array, dimension (N)
 The n diagonal elements of the diagonal matrix D from the
 factorization of A, as computed by SPTTRF.

E

 E is REAL array, dimension (N-1)
 The (n-1) off-diagonal elements of the unit bidiagonal factor
 U or L from the factorization of A, as computed by SPTTRF.

ANORM

 ANORM is REAL
 The 1-norm of the original matrix A.

RCOND

 RCOND is REAL
 The reciprocal of the condition number of the matrix A,
 computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is the
 1-norm of inv(A) computed in this routine.

WORK

 WORK is REAL 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:

September 2012

Further Details:

 The method used is described in Nicholas J. Higham, "Efficient
 Algorithms for Computing the Condition Number of a Tridiagonal
 Matrix", SIAM J. Sci. Stat. Comput., Vol. 7, No. 1, January 1986.

 

Definition at line 119 of file sptcon.f.

Author

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