Gabriele Cosmo
218 lines
6.1 KiB
Plaintext
218 lines
6.1 KiB
Plaintext
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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// * By copying, distributing or modifying the Program (or any work *
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// * based on the Program) you indicate your acceptance of this *
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// * statement, and all its terms. *
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// ********************************************************************
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//
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//
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// $Id: G4PolynomialSolver.icc,v 1.6 2001/07/11 10:00:40 gunter Exp $
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// GEANT4 tag $Name: geant4-05-00 $
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//
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// class G4PolynomialSolver
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//
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// 19.12.00 E.Medernach, First implementation
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//
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#define POLEPSILON 1e-12
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#define POLINFINITY 9.0E99
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#define ITERATION 12 // 20 But 8 is really enough for Newton with a good guess
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template <class T, class F>
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G4PolynomialSolver<T,F>::G4PolynomialSolver (T* typeF, F func, F deriv,
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G4double precision)
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{
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Precision = precision ;
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FunctionClass = typeF ;
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Function = func ;
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Derivative = deriv ;
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}
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template <class T, class F>
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G4PolynomialSolver<T,F>::~G4PolynomialSolver ()
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{
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}
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template <class T, class F>
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G4double G4PolynomialSolver<T,F>::solve(G4double IntervalMin,
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G4double IntervalMax)
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{
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return Newton(IntervalMin,IntervalMax);
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}
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/* If we want to be general this could work for any
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polynomial of order more that 4 if we find the (ORDER + 1)
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control points
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*/
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#define NBBEZIER 5
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template <class T, class F>
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G4int
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G4PolynomialSolver<T,F>::BezierClipping(/*T* typeF,F func,F deriv,*/
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G4double *IntervalMin,
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G4double *IntervalMax)
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{
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/** BezierClipping is a clipping interval Newton method **/
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/** It works by clipping the area where the polynomial is **/
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G4double P[NBBEZIER][2],D[2];
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G4double NewMin,NewMax;
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G4int IntervalIsVoid = 1;
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/*** Calculating Control Points ***/
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/* We see the polynomial as a Bezier curve for some control points to find */
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/*
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For 5 control points (polynomial of degree 4) this is:
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0 p0 = F((*IntervalMin))
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1/4 p1 = F((*IntervalMin)) + ((*IntervalMax) - (*IntervalMin))/4
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* F'((*IntervalMin))
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2/4 p2 = 1/6 * (16*F(((*IntervalMax) + (*IntervalMin))/2)
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- (p0 + 4*p1 + 4*p3 + p4))
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3/4 p3 = F((*IntervalMax)) - ((*IntervalMax) - (*IntervalMin))/4
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* F'((*IntervalMax))
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1 p4 = F((*IntervalMax))
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*/
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/* x,y,z,dx,dy,dz are constant during searching */
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D[0] = (FunctionClass->*Derivative)(*IntervalMin);
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P[0][0] = (*IntervalMin);
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P[0][1] = (FunctionClass->*Function)(*IntervalMin);
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if (fabs(P[0][1]) < Precision) {
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return 1;
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}
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if (((*IntervalMax) - (*IntervalMin)) < POLEPSILON) {
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return 1;
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}
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P[1][0] = (*IntervalMin) + ((*IntervalMax) - (*IntervalMin))/4;
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P[1][1] = P[0][1] + (((*IntervalMax) - (*IntervalMin))/4.0) * D[0];
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D[1] = (FunctionClass->*Derivative)(*IntervalMax);
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P[4][0] = (*IntervalMax);
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P[4][1] = (FunctionClass->*Function)(*IntervalMax);
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P[3][0] = (*IntervalMax) - ((*IntervalMax) - (*IntervalMin))/4;
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P[3][1] = P[4][1] - ((*IntervalMax) - (*IntervalMin))/4 * D[1];
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P[2][0] = ((*IntervalMax) + (*IntervalMin))/2;
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P[2][1] = (16*(FunctionClass->*Function)(((*IntervalMax)+(*IntervalMin))/2)
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- (P[0][1] + 4*P[1][1] + 4*P[3][1] + P[4][1]))/6 ;
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{
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G4double Intersection ;
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G4int i,j;
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NewMin = (*IntervalMax) ;
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NewMax = (*IntervalMin) ;
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for (i=0;i<5;i++)
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for (j=i+1;j<5;j++)
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{
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/* there is an intersection only if each have different signs */
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if (((P[j][1] > -Precision) && (P[i][1] < Precision)) ||
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((P[j][1] < Precision) && (P[i][1] > -Precision))) {
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IntervalIsVoid = 0;
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Intersection = P[j][0] - P[j][1]*((P[i][0] - P[j][0])/
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(P[i][1] - P[j][1]));
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if (Intersection < NewMin) {
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NewMin = Intersection;
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}
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if (Intersection > NewMax) {
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NewMax = Intersection;
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}
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}
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}
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if (IntervalIsVoid != 1) {
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(*IntervalMax) = NewMax;
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(*IntervalMin) = NewMin;
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}
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}
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if (IntervalIsVoid == 1) {
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return -1;
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}
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return 0;
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}
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template <class T, class F>
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G4double G4PolynomialSolver<T,F>::Newton (G4double IntervalMin,
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G4double IntervalMax)
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{
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/* So now we have a good guess and an interval where
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if there are an intersection the root must be */
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G4double Value = 0;
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G4double Gradient = 0;
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G4double Lambda ;
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G4int i=0;
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G4int j=0;
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/* Reduce interval before applying Newton Method */
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{
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G4int NewtonIsSafe ;
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while ((NewtonIsSafe = BezierClipping(&IntervalMin,&IntervalMax)) == 0) ;
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if (NewtonIsSafe == -1) {
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return POLINFINITY;
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}
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}
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Lambda = IntervalMin;
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Value = (FunctionClass->*Function)(Lambda);
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// while ((fabs(Value) > Precision)) {
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while (j != -1) {
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Value = (FunctionClass->*Function)(Lambda);
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Gradient = (FunctionClass->*Derivative)(Lambda);
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Lambda = Lambda - Value/Gradient ;
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if (fabs(Value) <= Precision) {
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j ++;
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if (j == 2) {
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j = -1;
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}
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} else {
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i ++;
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if (i > ITERATION)
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return POLINFINITY;
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}
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}
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return Lambda ;
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}
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