/* @(#)mrqmin.c	17.1.1.1 (ES0-DMD) 01/25/02 17:27:00 */
/*===========================================================================
  Copyright (C) 1995 European Southern Observatory (ESO)
 
  This program is free software; you can redistribute it and/or 
  modify it under the terms of the GNU General Public License as 
  published by the Free Software Foundation; either version 2 of 
  the License, or (at your option) any later version.
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public 
  License along with this program; if not, write to the Free 
  Software Foundation, Inc., 675 Massachusetss Ave, Cambridge, 
  MA 02139, USA.
 
  Corresponding concerning ESO-MIDAS should be addressed as follows:
	Internet e-mail: midas@eso.org
	Postal address: European Southern Observatory
			Data Management Division 
			Karl-Schwarzschild-Strasse 2
			D 85748 Garching bei Muenchen 
			GERMANY
===========================================================================*/

/* @(#)mrqmin.c	17.1.1.1  (ESO)  01/25/02  17:27:00 */

void mrqmin(x,y,sig,ndata,a,ma,lista,mfit,covar,alpha,chisq,funcs,alamda)
float x[],y[];
double sig[],a[],**covar,**alpha,*chisq,*alamda;
int ndata,ma,lista[],mfit;
void (*funcs)();
{
	int k,kk,j,ihit;
	static double *da,*atry,**oneda,*beta,ochisq;
	double *dvector(),**dmatrix();
	void mrqcof(),gaussj(),covsrt(),nrerror(),free_dmatrix(),free_dvector();
	if (*alamda < 0.0) {
		oneda=dmatrix(1,mfit,1,1);
		atry=dvector(1,ma);
		da=dvector(1,ma);
		beta=dvector(1,ma);
		kk=mfit+1;
		for (j=1;j<=ma;j++) {
			ihit=0;
			for (k=1;k<=mfit;k++)
				if (lista[k] == j) ihit++;
			if (ihit == 0)
				lista[kk++]=j;
			else if (ihit > 1) nrerror("Bad LISTA permutation in MRQMIN-1");
		}
		if (kk != ma+1) nrerror("Bad LISTA permutation in MRQMIN-2");
		*alamda=0.001;
		mrqcof(x,y,sig,ndata,a,ma,lista,mfit,alpha,beta,chisq,funcs);
		ochisq=(*chisq);
	}
	for (j=1;j<=mfit;j++) {
		for (k=1;k<=mfit;k++) covar[j][k]=alpha[j][k];
		covar[j][j]=alpha[j][j]*(1.0+(*alamda));
		oneda[j][1]=beta[j];
	}
	gaussj(covar,mfit,oneda,1);
	for (j=1;j<=mfit;j++)
		da[j]=oneda[j][1];
	if (*alamda == 0.0) {
		covsrt(covar,ma,lista,mfit);
		free_dvector(beta,1,ma);
		free_dvector(da,1,ma);
		free_dvector(atry,1,ma);
		free_dmatrix(oneda,1,mfit,1,1);
		return;
	}
	for (j=1;j<=ma;j++) atry[j]=a[j];
	for (j=1;j<=mfit;j++)
		atry[lista[j]] = a[lista[j]]+da[j];
	mrqcof(x,y,sig,ndata,atry,ma,lista,mfit,covar,da,chisq,funcs);
	if (*chisq < ochisq) {
		*alamda *= 0.1;
		ochisq=(*chisq);
		for (j=1;j<=mfit;j++) {
			for (k=1;k<=mfit;k++) alpha[j][k]=covar[j][k];
			beta[j]=da[j];
			a[lista[j]]=atry[lista[j]];
		}
	} else {
		*alamda *= 10.0;
		*chisq=ochisq;
	}
	return;
}