ScanBuilder.java

package org.freehep.math.minuit;

import java.util.ArrayList;
import java.util.List;

/** Performs a minimization using the simplex method of Nelder and Mead
 * (ref. Comp. J. 7, 308 (1965)).
 * @version $Id: ScanBuilder.java 8584 2006-08-10 23:06:37Z duns $
 */
class ScanBuilder implements MinimumBuilder
{
   public FunctionMinimum minimum(MnFcn mfcn, GradientCalculator gc,  MinimumSeed seed,  MnStrategy stra,  int maxfcn, double toler)
   {
      MnAlgebraicVector x = seed.parameters().vec().clone();
      MnUserParameterState upst = new MnUserParameterState(seed.state(), mfcn.errorDef(), seed.trafo());
      MnParameterScan scan = new MnParameterScan(mfcn.fcn(), upst.parameters(), seed.fval());
      double amin = scan.fval();
      int n = seed.trafo().variableParameters();
      MnAlgebraicVector dirin = new MnAlgebraicVector(n);
      for(int i = 0; i < n; i++)
      {
         int ext = seed.trafo().extOfInt(i);
         scan.scan(ext);
         if(scan.fval() < amin)
         {
            amin = scan.fval();
            x.set(i,seed.trafo().ext2int(ext, scan.parameters().value(ext)));
         }
         dirin.set(i, Math.sqrt(2.*mfcn.errorDef()*seed.error().invHessian().get(i,i)));
      }
      
      MinimumParameters mp = new MinimumParameters(x, dirin, amin);
      MinimumState st = new MinimumState(mp, 0., mfcn.numOfCalls());
      
      List<MinimumState> states = new ArrayList<MinimumState>(1);
      states.add(st);
      return new FunctionMinimum(seed, states, mfcn.errorDef());
   }
   
}