DTPT01
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
November 2006
Purpose
DTPT01 computes the residual for a triangular matrix A times its
inverse when A is stored in packed format:
RESID = norm(A*AINV - I) / ( N * norm(A) * norm(AINV) * EPS ),
where EPS is the machine epsilon.
inverse when A is stored in packed format:
RESID = norm(A*AINV - I) / ( N * norm(A) * norm(AINV) * EPS ),
where EPS is the machine epsilon.
Arguments
| UPLO |
(input) CHARACTER*1
Specifies whether the matrix A is upper or lower triangular.
= 'U': Upper triangular = 'L': Lower triangular |
| DIAG |
(input) CHARACTER*1
Specifies whether or not the matrix A is unit triangular.
= 'N': Non-unit triangular = 'U': Unit triangular |
| N |
(input) INTEGER
The order of the matrix A. N >= 0.
|
| AP |
(input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
The original upper or lower triangular matrix A, packed
columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP((j-1)*j/2 + i) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP((j-1)*(n-j) + j*(j+1)/2 + i-j) = A(i,j) for j<=i<=n. |
| AINVP |
(input/output) DOUBLE PRECISION array, dimension (N*(N+1)/2)
On entry, the (triangular) inverse of the matrix A, packed
columnwise in a linear array as in AP. On exit, the contents of AINVP are destroyed. |
| RCOND |
(output) DOUBLE PRECISION
The reciprocal condition number of A, computed as
1/(norm(A) * norm(AINV)). |
| WORK |
(workspace) DOUBLE PRECISION array, dimension (N)
|
| RESID |
(output) DOUBLE PRECISION
norm(A*AINV - I) / ( N * norm(A) * norm(AINV) * EPS )
|