lsd_mkb/lsd_mkb_superlu/superlu_seq/dgsequ.c File Reference

#include <math.h>
#include "slu_ddefs.h"

Include dependency graph for dgsequ.c:

Functions
void	dgsequ (SuperMatrix *A, double *r, double *c, double *rowcnd, double *colcnd, double *amax, int *info)
	Driver related.

---

Function Documentation

void dgsequ	(	SuperMatrix *	A,
		double *	r,
		double *	c,
		double *	rowcnd,
		double *	colcnd,
		double *	amax,
		int *	info
	)

Driver related.

 Purpose   
   =======

   DGSEQU 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.

   Arguments   
   =========

   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_D; Mtype = SLU_GE.

   R       (output) double*, size A->nrow
           If INFO = 0 or INFO > M, R contains the row scale factors   
           for A.

   C       (output) double*, size A->ncol
           If INFO = 0,  C contains the column scale factors for A.

   ROWCND  (output) double*
           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) double*
           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) double*
           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

   ===================================================================== 
 

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