dptt01.f - Man Page

subroutine dptt01 (n, d, e, df, ef, work, resid)
DPTT01

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

N

          N is INTEGER
          The order of the matrix A.

D

          D is DOUBLE PRECISION array, dimension (N)
          The n diagonal elements of the tridiagonal matrix A.

E

          E is DOUBLE PRECISION array, dimension (N-1)
          The (n-1) subdiagonal elements of the tridiagonal matrix A.

DF

          DF is DOUBLE PRECISION array, dimension (N)
          The n diagonal elements of the factor L from the L*D*L'
          factorization of A.

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.

WORK

          WORK is DOUBLE PRECISION array, dimension (2*N)

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.

Definition at line 90 of file dptt01.f.