DPTT02
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
November 2006
Purpose
DPTT02 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.
tridiagonal system of equations:
RESID = norm(B - A*X) / (norm(A) * norm(X) * EPS),
where EPS is the machine epsilon.
Arguments
| N |
(input) INTEGTER
The order of the matrix A.
|
| NRHS |
(input) INTEGER
The number of right hand sides, i.e., the number of columns
of the matrices B and X. NRHS >= 0. |
| D |
(input) DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the tridiagonal matrix A.
|
| E |
(input) DOUBLE PRECISION array, dimension (N-1)
The (n-1) subdiagonal elements of the tridiagonal matrix A.
|
| X |
(input) DOUBLE PRECISION array, dimension (LDX,NRHS)
The n by nrhs matrix of solution vectors X.
|
| LDX |
(input) INTEGER
The leading dimension of the array X. LDX >= max(1,N).
|
| B |
(input/output) DOUBLE PRECISION 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 |
(input) INTEGER
The leading dimension of the array B. LDB >= max(1,N).
|
| RESID |
(output) DOUBLE PRECISION
norm(B - A*X) / (norm(A) * norm(X) * EPS)
|