SPTCON (3)  Linux Man Pages
NAME
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 1norm) 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.
DD is REAL array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization of A, as computed by SPTTRF.
EE is REAL array, dimension (N1) The (n1) offdiagonal elements of the unit bidiagonal factor U or L from the factorization of A, as computed by SPTTRF.
ANORMANORM is REAL The 1norm of the original matrix A.
RCONDRCOND is REAL The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is the 1norm of inv(A) computed in this routine.
WORKWORK is REAL array, dimension (N)
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith 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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