/*! \file
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 3.0) --
 * Lawrence Berkeley National Lab, Univ. of California Berkeley,
 * and Xerox Palo Alto Research Center.
 * September 10, 2007
 *
 */
/*
 * File name:	slaqgs.c
 * History:     Modified from LAPACK routine SLAQGE
 */
#include <math.h>
#include "slu_mt_sdefs.h"


void
slaqgs(SuperMatrix *A, float *r, float *c, 
	float rowcnd, float colcnd, float amax, equed_t *equed)
{
/*
    Purpose   
    =======   

    slaqgs() 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 = SLU_NC; Dtype = SLU_S; Mtype = SLU_GE.
	    
    R       (input) float*, dimension (A->nrow)
            The row scale factors for A.
	    
    C       (input) float*, dimension (A->ncol)
            The column scale factors for A.
	    
    ROWCND  (input) float
            Ratio of the smallest R(i) to the largest R(i).
	    
    COLCND  (input) float
            Ratio of the smallest C(i) to the largest C(i).
	    
    AMAX    (input) float
            Absolute value of largest matrix entry.
	    
    EQUED   (output) equed_t*
            Specifies the form of equilibration that was done.   
            = NOEQUIL: No equilibration
            = ROW:  Row equilibration, i.e., A has been premultiplied by
                    diag(R).   
            = COL:  Column equilibration, i.e., A has been postmultiplied
                    by diag(C).   
            = BOTH: Both row and column equilibration, i.e., A has been
                    replaced by diag(R) * A * diag(C).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.   

    ===================================================================== 
*/

#define THRESH    (0.1)
    
    /* Local variables */
    NCformat *Astore;
    float   *Aval;
    int_t i, j, irow;
    float large, small, cj;
    extern double slamch_(char *);


    /* Quick return if possible */
    if (A->nrow <= 0 || A->ncol <= 0) {
	*equed = NOEQUIL;
	return;
    }

    Astore = A->Store;
    Aval = Astore->nzval;
    
    /* Initialize LARGE and SMALL. */
    small = slamch_("Safe minimum") / slamch_("Precision");
    large = 1. / small;

    if (rowcnd >= THRESH && amax >= small && amax <= large) {
	if (colcnd >= THRESH)
	    *equed = NOEQUIL;
	else {
	    /* Column scaling */
	    for (j = 0; j < A->ncol; ++j) {
		cj = c[j];
		for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; ++i) {
		    Aval[i] *= cj;
                }
	    }
	    *equed = COL;
	}
    } else if (colcnd >= THRESH) {
	/* Row scaling, no column scaling */
	for (j = 0; j < A->ncol; ++j)
	    for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; ++i) {
		irow = Astore->rowind[i];
		Aval[i] *= r[irow];
	    }
	*equed = ROW;
    } else {
	/* Row and column scaling */
	for (j = 0; j < A->ncol; ++j) {
	    cj = c[j];
	    for (i = Astore->colptr[j]; i < Astore->colptr[j+1]; ++i) {
		irow = Astore->rowind[i];
		Aval[i] *= cj * r[irow];
	    }
	}
	*equed = BOTH;
    }

    return;

} /* slaqgs */

