zptcon (l)  Linux Man Pages
zptcon: computes the reciprocal of the condition number (in the 1norm) of a complex Hermitian positive definite tridiagonal matrix using the factorization A = L*D*L**H or A = U**H*D*U computed by ZPTTRF
NAME
ZPTCON  computes the reciprocal of the condition number (in the 1norm) of a complex Hermitian positive definite tridiagonal matrix using the factorization A = L*D*L**H or A = U**H*D*U computed by ZPTTRFSYNOPSIS
 SUBROUTINE ZPTCON(
 N, D, E, ANORM, RCOND, RWORK, INFO )
 INTEGER INFO, N
 DOUBLE PRECISION ANORM, RCOND
 DOUBLE PRECISION D( * ), RWORK( * )
 COMPLEX*16 E( * )
PURPOSE
ZPTCON computes the reciprocal of the condition number (in the 1norm) of a complex Hermitian positive definite tridiagonal matrix using the factorization A = L*D*L**H or A = U**H*D*U computed by ZPTTRF. Norm(inv(A)) is computed by a direct method, and the reciprocal of the condition number is computed asARGUMENTS
 N (input) INTEGER
 The order of the matrix A. N >= 0.
 D (input) DOUBLE PRECISION array, dimension (N)
 The n diagonal elements of the diagonal matrix D from the factorization of A, as computed by ZPTTRF.
 E (input) COMPLEX*16 array, dimension (N1)
 The (n1) offdiagonal elements of the unit bidiagonal factor U or L from the factorization of A, as computed by ZPTTRF.
 ANORM (input) DOUBLE PRECISION
 The 1norm of the original matrix A.
 RCOND (output) DOUBLE PRECISION
 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.
 RWORK (workspace) DOUBLE PRECISION array, dimension (N)
 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
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.