SLAGSY
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
November 2006
Purpose
SLAGSY generates a real symmetric matrix A, by pre- and post-
multiplying a real diagonal matrix D with a random orthogonal matrix:
A = U*D*U'. The semi-bandwidth may then be reduced to k by additional
orthogonal transformations.
multiplying a real diagonal matrix D with a random orthogonal matrix:
A = U*D*U'. The semi-bandwidth may then be reduced to k by additional
orthogonal transformations.
Arguments
| N |
(input) INTEGER
The order of the matrix A. N >= 0.
|
| K |
(input) INTEGER
The number of nonzero subdiagonals within the band of A.
0 <= K <= N-1. |
| D |
(input) REAL array, dimension (N)
The diagonal elements of the diagonal matrix D.
|
| A |
(output) REAL array, dimension (LDA,N)
The generated n by n symmetric matrix A (the full matrix is
stored). |
| LDA |
(input) INTEGER
The leading dimension of the array A. LDA >= N.
|
| ISEED |
(input/output) INTEGER array, dimension (4)
On entry, the seed of the random number generator; the array
elements must be between 0 and 4095, and ISEED(4) must be odd. On exit, the seed is updated. |
| WORK |
(workspace) REAL array, dimension (2*N)
|
| INFO |
(output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value |