SPBT02
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
November 2006
Purpose
SPBT02 computes the residual for a solution of a symmetric banded
system of equations A*x = b:
RESID = norm( B - A*X ) / ( norm(A) * norm(X) * EPS)
where EPS is the machine precision.
system of equations A*x = b:
RESID = norm( B - A*X ) / ( norm(A) * norm(X) * EPS)
where EPS is the machine precision.
Arguments
| UPLO |
(input) CHARACTER*1
Specifies whether the upper or lower triangular part of the
symmetric matrix A is stored: = 'U': Upper triangular = 'L': Lower triangular |
| N |
(input) INTEGER
The number of rows and columns of the matrix A. N >= 0.
|
| KD |
(input) INTEGER
The number of super-diagonals of the matrix A if UPLO = 'U',
or the number of sub-diagonals if UPLO = 'L'. KD >= 0. |
| A |
(input) REAL array, dimension (LDA,N)
The original symmetric band matrix A. If UPLO = 'U', the
upper triangular part of A is stored as a band matrix; if UPLO = 'L', the lower triangular part of A is stored. The columns of the appropriate triangle are stored in the columns of A and the diagonals of the triangle are stored in the rows of A. See SPBTRF for further details. |
| LDA |
(input) INTEGER.
The leading dimension of the array A. LDA >= max(1,KD+1).
|
| X |
(input) REAL array, dimension (LDX,NRHS)
The computed solution vectors for the system of linear
equations. |
| LDX |
(input) INTEGER
The leading dimension of the array X. LDX >= max(1,N).
|
| B |
(input/output) 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 - A*X. |
| LDB |
(input) INTEGER
The leading dimension of the array B. LDB >= max(1,N).
|
| RWORK |
(workspace) REAL array, dimension (N)
|
| RESID |
(output) REAL
The maximum over the number of right hand sides of
norm(B - A*X) / ( norm(A) * norm(X) * EPS ). |