zptcon.f File Reference

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Functions/Subroutines
subroutine	ZPTCON (N, D, E, ANORM, RCOND, RWORK, INFO)
	ZPTCON

---

Function/Subroutine Documentation

subroutine ZPTCON	(	INTEGER	N,
		DOUBLE PRECISION, dimension( * )	D,
		COMPLEX*16, dimension( * )	E,
		DOUBLE PRECISION	ANORM,
		DOUBLE PRECISION	RCOND,
		DOUBLE PRECISION, dimension( * )	RWORK,
		INTEGER	INFO
	)

ZPTCON

Download ZPTCON + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 ZPTCON computes the reciprocal of the condition number (in the
 1-norm) 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 as
                  RCOND = 1 / (ANORM * norm(inv(A))).
 

Parameters:

[in]	N	N is INTEGER The order of the matrix A. N >= 0.
[in]	D	D is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization of A, as computed by ZPTTRF.
[in]	E	E is COMPLEX*16 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 ZPTTRF.
[in]	ANORM	ANORM is DOUBLE PRECISION The 1-norm of the original matrix A.
[out]	RCOND	RCOND is DOUBLE PRECISION 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.
[out]	RWORK	RWORK is DOUBLE PRECISION array, dimension (N)
[out]	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

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 120 of file zptcon.f.

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