zero_list.C

/*
 * Function zero_list 
 * Locates approximatively all the zeros of a function in a given interval
 * 
 * (see file utilitaires.h for documentation)
 *
 */


/*
 *   Copyright (c) 2003 Eric Gourgoulhon
 *
 *   This file is part of LORENE.
 *
 *   LORENE 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.
 *
 *   LORENE 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 LORENE; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

char zero_list_C[] = "$Header: /cvsroot/Lorene/C++/Source/Non_class_members/Utilities/zero_list.C,v 1.1 2003/09/08 20:22:02 e_gourgoulhon Exp $" ;


/*
 * $Id: zero_list.C,v 1.1 2003/09/08 20:22:02 e_gourgoulhon Exp $
 * $Log: zero_list.C,v $
 * Revision 1.1  2003/09/08 20:22:02  e_gourgoulhon
 * First version
 *
 *
 * $Header: /cvsroot/Lorene/C++/Source/Non_class_members/Utilities/zero_list.C,v 1.1 2003/09/08 20:22:02 e_gourgoulhon Exp $
 *
 */


// Headers Lorene 
#include "param.h"
#include "tbl.h"

//****************************************************************************

void zero_list( double (*f)(double, const Param&), const Param& par,
        double xmin, double xmax, int nsub, 
        Tbl*& az, Tbl*& bz ) {
        
    int nzero = 0 ; 
    
    double dx = (xmax-xmin) / double(nsub) ;     
    double f1 = f(xmin, par) ;
    double x1 = xmin ; 
    double x2 = xmin + dx ; 
    
    double* borne_inf = new double[nsub] ;   // At maximum nsub zeros
    double* borne_sup = new double[nsub] ;      
    
    for (int i=0; i<nsub; i++) {
    double f2 = f(x2, par) ;
    if (f1*f2 < 0.) {       // A zero has been found
        borne_inf[nzero] = x1 ; 
        borne_sup[nzero] = x2 ; 
        nzero += 1 ;    
    } 
    // Next sub-interval :
    x1 = x2 ; 
    f1 = f2 ;  
    x2 += dx ;
    } 

    // Result:

    az = new Tbl(nzero) ; 
    bz = new Tbl(nzero) ; 
    
    if (nzero > 0) {

    az->set_etat_qcq() ; 
    bz->set_etat_qcq() ; 

    for (int i=0; i<nzero; i++) {
        az->set(i) = borne_inf[i] ;
        bz->set(i) = borne_sup[i] ;
    }
    }
    
    delete [] borne_inf ; 
    delete [] borne_sup ; 
    
}  

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