sgtt01()

subroutine sgtt01	(	integer	N,
		real, dimension( * )	DL,
		real, dimension( * )	D,
		real, dimension( * )	DU,
		real, dimension( * )	DLF,
		real, dimension( * )	DF,
		real, dimension( * )	DUF,
		real, dimension( * )	DU2,
		integer, dimension( * )	IPIV,
		real, dimension( ldwork, * )	WORK,
		integer	LDWORK,
		real, dimension( * )	RWORK,
		real	RESID
	)

SGTT01

Purpose:

 SGTT01 reconstructs a tridiagonal matrix A from its LU factorization
 and computes the residual
    norm(L*U - A) / ( norm(A) * EPS ),
 where EPS is the machine epsilon.

Parameters

[in]	N	N is INTEGTER The order of the matrix A. N >= 0.
[in]	DL	DL is REAL array, dimension (N-1) The (n-1) sub-diagonal elements of A.
[in]	D	D is REAL array, dimension (N) The diagonal elements of A.
[in]	DU	DU is REAL array, dimension (N-1) The (n-1) super-diagonal elements of A.
[in]	DLF	DLF is REAL array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A.
[in]	DF	DF is REAL array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A.
[in]	DUF	DUF is REAL array, dimension (N-1) The (n-1) elements of the first super-diagonal of U.
[in]	DU2	DU2 is REAL array, dimension (N-2) The (n-2) elements of the second super-diagonal of U.
[in]	IPIV	IPIV is INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.
[out]	WORK	WORK is REAL array, dimension (LDWORK,N)
[in]	LDWORK	LDWORK is INTEGER The leading dimension of the array WORK. LDWORK >= max(1,N).
[out]	RWORK	RWORK is REAL array, dimension (N)
[out]	RESID	RESID is REAL The scaled residual: norm(L*U - A) / (norm(A) * EPS)

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.