|void||sgsequ (SuperMatrix *A, float *r, float *c, float *rowcnd, float *colcnd, float *amax, int *info)|
|Driver related. |
-- SuperLU routine (version 2.0) -- Univ. of California Berkeley, Xerox Palo Alto Research Center, and Lawrence Berkeley National Lab. November 15, 1997
Modified from LAPACK routine SGEEQU
|void sgsequ||(||SuperMatrix *||A,|
SGSEQU computes row and column scalings intended to equilibrate an M-by-N sparse matrix A and reduce its condition number. R returns the row scale factors and C the column scale factors, chosen to try to make the largest element in each row and column of the matrix B with elements B(i,j)=R(i)*A(i,j)*C(j) have absolute value 1.
R(i) and C(j) are restricted to be between SMLNUM = smallest safe number and BIGNUM = largest safe number. Use of these scaling factors is not guaranteed to reduce the condition number of A but works well in practice.
See supermatrix.h for the definition of 'SuperMatrix' structure.
A (input) SuperMatrix* The matrix of dimension (A->nrow, A->ncol) whose equilibration factors are to be computed. The type of A can be: Stype = SLU_NC; Dtype = SLU_S; Mtype = SLU_GE.
R (output) float*, size A->nrow If INFO = 0 or INFO > M, R contains the row scale factors for A.
C (output) float*, size A->ncol If INFO = 0, C contains the column scale factors for A.
ROWCND (output) float* If INFO = 0 or INFO > M, ROWCND contains the ratio of the smallest R(i) to the largest R(i). If ROWCND >= 0.1 and AMAX is neither too large nor too small, it is not worth scaling by R.
COLCND (output) float* If INFO = 0, COLCND contains the ratio of the smallest C(i) to the largest C(i). If COLCND >= 0.1, it is not worth scaling by C.
AMAX (output) float* Absolute value of largest matrix element. If AMAX is very close to overflow or very close to underflow, the matrix should be scaled.
INFO (output) int* = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, and i is <= A->nrow: the i-th row of A is exactly zero > A->ncol: the (i-M)-th column of A is exactly zero