dptt01()

subroutine dptt01	(	integer	N,
		double precision, dimension( * )	D,
		double precision, dimension( * )	E,
		double precision, dimension( * )	DF,
		double precision, dimension( * )	EF,
		double precision, dimension( * )	WORK,
		double precision	RESID
	)

DPTT01

Purpose:

 DPTT01 reconstructs a tridiagonal matrix A from its L*D*L'
 factorization and computes the residual
    norm(L*D*L' - A) / ( n * norm(A) * EPS ),
 where EPS is the machine epsilon.

Parameters

[in]	N	N is INTEGTER The order of the matrix A.
[in]	D	D is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the tridiagonal matrix A.
[in]	E	E is DOUBLE PRECISION array, dimension (N-1) The (n-1) subdiagonal elements of the tridiagonal matrix A.
[in]	DF	DF is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the factor L from the L*D*L' factorization of A.
[in]	EF	EF is DOUBLE PRECISION array, dimension (N-1) The (n-1) subdiagonal elements of the factor L from the L*D*L' factorization of A.
[out]	WORK	WORK is DOUBLE PRECISION array, dimension (2*N)
[out]	RESID	RESID is DOUBLE PRECISION norm(L*D*L' - A) / (n * norm(A) * EPS)

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.