zptt02.f - Man Page

subroutine zptt02 (uplo, n, nrhs, d, e, x, ldx, b, ldb, resid)
ZPTT02

ZPTT02

Purpose:

 ZPTT02 computes the residual for the solution to a symmetric
 tridiagonal system of equations:
    RESID = norm(B - A*X) / (norm(A) * norm(X) * EPS),
 where EPS is the machine epsilon.

Parameters

UPLO

          UPLO is CHARACTER*1
          Specifies whether the superdiagonal or the subdiagonal of the
          tridiagonal matrix A is stored.
          = 'U':  E is the superdiagonal of A
          = 'L':  E is the subdiagonal of A

N

          N is INTEGER
          The order of the matrix A.

NRHS

          NRHS is INTEGER
          The number of right hand sides, i.e., the number of columns
          of the matrices B and X.  NRHS >= 0.

D

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

E

          E is COMPLEX*16 array, dimension (N-1)
          The (n-1) subdiagonal elements of the tridiagonal matrix A.

X

          X is COMPLEX*16 array, dimension (LDX,NRHS)
          The n by nrhs matrix of solution vectors X.

LDX

          LDX is INTEGER
          The leading dimension of the array X.  LDX >= max(1,N).

B

          B is COMPLEX*16 array, dimension (LDB,NRHS)
          On entry, the n by nrhs matrix of right hand side vectors B.
          On exit, B is overwritten with the difference B - A*X.

LDB

          LDB is INTEGER
          The leading dimension of the array B.  LDB >= max(1,N).

RESID

          RESID is DOUBLE PRECISION
          norm(B - A*X) / (norm(A) * norm(X) * EPS)

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 114 of file zptt02.f.