dlaqgs.c File Reference

Equlibrates a general sprase matrix. More...

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

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Macros
#define	THRESH   (0.1)

Functions
void	dlaqgs (SuperMatrix *A, double *r, double *c, double rowcnd, double colcnd, double amax, char *equed)

Detailed Description

Copyright (c) 2003, The Regents of the University of California, through Lawrence Berkeley National Laboratory (subject to receipt of any required approvals from U.S. Dept. of Energy)

All rights reserved.

The source code is distributed under BSD license, see the file License.txt at the top-level directory.

– 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 DLAQGE

Macro Definition Documentation

#define THRESH   (0.1)

Function Documentation

void dlaqgs	(	SuperMatrix *	A,
		double *	r,
		double *	c,
		double	rowcnd,
		double	colcnd,
		double	amax,
		char *	equed
	)

Purpose   

  DLAQGS equilibrates a general sparse M by N matrix A using the row and   
  scaling factors in the vectors R and C.

  See supermatrix.h for the definition of 'SuperMatrix' structure.

Arguments   

  A       (input/output) SuperMatrix*
          On exit, the equilibrated matrix.  See EQUED for the form of 
          the equilibrated matrix. The type of A can be:
         Stype = NC; Dtype = SLU_D; Mtype = GE.

  R       (input) double*, dimension (A->nrow)
          The row scale factors for A.

  C       (input) double*, dimension (A->ncol)
          The column scale factors for A.

  ROWCND  (input) double
          Ratio of the smallest R(i) to the largest R(i).

  COLCND  (input) double
          Ratio of the smallest C(i) to the largest C(i).

  AMAX    (input) double
          Absolute value of largest matrix entry.

  EQUED   (output) char*
          Specifies the form of equilibration that was done.   
          = 'N':  No equilibration   
          = 'R':  Row equilibration, i.e., A has been premultiplied by  
                  diag(R).   
          = 'C':  Column equilibration, i.e., A has been postmultiplied  
                  by diag(C).   
          = 'B':  Both row and column equilibration, i.e., A has been
                  replaced by diag(R) * A * diag(C).

Internal Parameters   

  THRESH is a threshold value used to decide if row or column scaling   
  should be done based on the ratio of the row or column scaling   
  factors.  If ROWCND < THRESH, row scaling is done, and if   
  COLCND < THRESH, column scaling is done.

  LARGE and SMALL are threshold values used to decide if row scaling   
  should be done based on the absolute size of the largest matrix   
  element.  If AMAX > LARGE or AMAX < SMALL, row scaling is done.   

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