DLAQSY
November 2006
Purpose
DLAQSY equilibrates a symmetric matrix A using the scaling factors
in the vector S.
in the vector S.
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 order of the matrix A. N >= 0.
|
| A |
(input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the symmetric matrix A. If UPLO = 'U', the leading
n by n upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n by n lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if EQUED = 'Y', the equilibrated matrix: diag(S) * A * diag(S). |
| LDA |
(input) INTEGER
The leading dimension of the array A. LDA >= max(N,1).
|
| S |
(input) DOUBLE PRECISION array, dimension (N)
The scale factors for A.
|
| SCOND |
(input) DOUBLE PRECISION
Ratio of the smallest S(i) to the largest S(i).
|
| AMAX |
(input) DOUBLE PRECISION
Absolute value of largest matrix entry.
|
| EQUED |
(output) CHARACTER*1
Specifies whether or not equilibration was done.
= 'N': No equilibration. = 'Y': Equilibration was done, i.e., A has been replaced by diag(S) * A * diag(S). |
Internal Parameters
THRESH is a threshold value used to decide if scaling should be done
based on the ratio of the scaling factors. If SCOND < THRESH,
scaling is done.
LARGE and SMALL are threshold values used to decide if scaling should
be done based on the absolute size of the largest matrix element.
If AMAX > LARGE or AMAX < SMALL, scaling is done.
based on the ratio of the scaling factors. If SCOND < THRESH,
scaling is done.
LARGE and SMALL are threshold values used to decide if scaling should
be done based on the absolute size of the largest matrix element.
If AMAX > LARGE or AMAX < SMALL, scaling is done.