DLAQSP
November 2006
Purpose
DLAQSP 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.
|
| AP |
(input/output) DOUBLE PRECISION array, dimension (N*(N+1)/2)
On entry, the upper or lower triangle of the symmetric 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(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. On exit, the equilibrated matrix: diag(S) * A * diag(S), in the same storage format as A. |
| 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 = 'Y': Equilibration was done, i.e., A has been replaced by diag(S) * A * diag(S).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.