sgtt02.f - Man Page

subroutine sgtt02 (trans, n, nrhs, dl, d, du, x, ldx, b, ldb, resid)
SGTT02

SGTT02

Purpose:

 SGTT02 computes the residual for the solution to a tridiagonal
 system of equations:
    RESID = norm(B - op(A)*X) / (norm(op(A)) * norm(X) * EPS),
 where EPS is the machine epsilon.
 The norm used is the 1-norm.

Parameters

TRANS

          TRANS is CHARACTER
          Specifies the form of the residual.
          = 'N':  B - A    * X  (No transpose)
          = 'T':  B - A**T * X  (Transpose)
          = 'C':  B - A**H * X  (Conjugate transpose = Transpose)

N

          N is INTEGER
          The order of the matrix A.  N >= 0.

NRHS

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

DL

          DL is REAL array, dimension (N-1)
          The (n-1) sub-diagonal elements of A.

D

          D is REAL array, dimension (N)
          The diagonal elements of A.

DU

          DU is REAL array, dimension (N-1)
          The (n-1) super-diagonal elements of A.

X

          X is REAL array, dimension (LDX,NRHS)
          The computed solution vectors X.

LDX

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

B

          B is REAL array, dimension (LDB,NRHS)
          On entry, the right hand side vectors for the system of
          linear equations.
          On exit, B is overwritten with the difference B - op(A)*X.

LDB

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

RESID

          RESID is REAL
          norm(B - op(A)*X) / (norm(op(A)) * norm(X) * EPS)

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 123 of file sgtt02.f.