SimplexSeedGenerator.cxx

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// @(#)root/minuit2:$Id$
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei   2003-2005
 
/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/
 
#include "Minuit2/SimplexSeedGenerator.h"
#include "Minuit2/MnUserParameterState.h"
#include "Minuit2/MnFcn.h"
#include "Minuit2/MinimumSeed.h"
#include "Minuit2/MnStrategy.h"
#include "Minuit2/InitialGradientCalculator.h"
#include "Minuit2/VariableMetricEDMEstimator.h"
 
namespace ROOT {
 
namespace Minuit2 {
 
MinimumSeed SimplexSeedGenerator::
operator()(const MnFcn &fcn, const GradientCalculator &, const MnUserParameterState &st, const MnStrategy &) const
{
   // create starting state for Simplex, which corresponds to the initial parameter values
   // using the simple Initial gradient calculator (does not use any FCN function calls)
   unsigned int n = st.VariableParameters();
   const MnMachinePrecision &prec = st.Precision();
 
   // initial starting values
   MnAlgebraicVector x(st.IntParameters());
   double fcnmin = MnFcnCaller{fcn}(x);
   MinimumParameters pa(x, fcnmin);
   FunctionGradient dgrad = calculateInitialGradient(pa, st.Trafo(), fcn.ErrorDef());
   MnAlgebraicSymMatrix mat(n);
   double dcovar = 1.;
   for (unsigned int i = 0; i < n; i++)
      mat(i, i) = (std::fabs(dgrad.G2()(i)) > prec.Eps2() ? 1. / dgrad.G2()(i) : 1.);
   MinimumError err(mat, dcovar);
   double edm = VariableMetricEDMEstimator().Estimate(dgrad, err);
   MinimumState state(pa, err, dgrad, edm, fcn.NumOfCalls());
 
   return MinimumSeed(state, st.Trafo());
}
 
} // namespace Minuit2
 
} // namespace ROOT