Line data    Source code

       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             :    Copyright (c) 2015-2023 The plumed team
       3             :    (see the PEOPLE file at the root of the distribution for a list of names)
       4             : 
       5             :    See http://www.plumed.org for more information.
       6             : 
       7             :    This file is part of plumed, version 2.
       8             : 
       9             :    plumed is free software: you can redistribute it and/or modify
      10             :    it under the terms of the GNU Lesser General Public License as published by
      11             :    the Free Software Foundation, either version 3 of the License, or
      12             :    (at your option) any later version.
      13             : 
      14             :    plumed is distributed in the hope that it will be useful,
      15             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
      16             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      17             :    GNU Lesser General Public License for more details.
      18             : 
      19             :    You should have received a copy of the GNU Lesser General Public License
      20             :    along with plumed.  If not, see <http://www.gnu.org/licenses/>.
      21             : +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
      22             : #ifndef __PLUMED_tools_ConjugateGradient_h
      23             : #define __PLUMED_tools_ConjugateGradient_h
      24             : 
      25             : #include "MinimiseBase.h"
      26             : 
      27             : namespace PLMD {
      28             : 
      29             : template <class FCLASS>
      30             : class ConjugateGradient : public MinimiseBase<FCLASS> {
      31             : private:
      32             : /// This is the pointer to the member function in the energy
      33             : /// calculating class that calculates the energy
      34             :   typedef double(FCLASS::*engf_pointer)( const std::vector<double>& p, std::vector<double>& der );
      35             :   const unsigned ITMAX;
      36             :   const double EPS;
      37             : public:
      38         505 :   explicit ConjugateGradient( FCLASS* funcc ) : MinimiseBase<FCLASS>(funcc), ITMAX(200), EPS(1E-10) {}
      39             :   void minimise( const double& ftol, std::vector<double>& p, engf_pointer myfunc );
      40             : };
      41             : 
      42             : template <class FCLASS>
      43         526 : void ConjugateGradient<FCLASS>::minimise( const double& ftol, std::vector<double>& p, engf_pointer myfunc ) {
      44         526 :   std::vector<double> xi( p.size() ), g( p.size() ), h( p.size() );
      45         526 :   double fp = this->calcDerivatives( p, xi, myfunc );
      46        6826 :   for(unsigned j=0; j<p.size(); ++j) { g[j] = -xi[j]; xi[j]=h[j]=g[j]; }
      47             : 
      48         897 :   for(unsigned its=0; its<ITMAX; ++its) {
      49         897 :     double fret=this->linemin( xi, p, myfunc );
      50             :     // The exit condition
      51         897 :     if( 2.0*std::fabs(fret-fp) <= ftol*(std::fabs(fret)+std::fabs(fp)+EPS)) { return; }
      52         371 :     fp = fret; this->calcDerivatives( p, xi, myfunc );
      53             :     double ddg=0., gg=0.;
      54       12899 :     for(unsigned j=0; j<p.size(); ++j) { gg += g[j]*g[j]; ddg += (xi[j]+g[j])*xi[j]; }
      55             : 
      56         371 :     if( gg==0.0 ) return;
      57             : 
      58         371 :     double gam=ddg/gg;
      59       12899 :     for(unsigned j=0; j<p.size(); ++j) { g[j] = -xi[j]; xi[j]=h[j]=g[j]+gam*h[j]; }
      60             :   }
      61           0 :   plumed_merror("Too many interactions in conjugate gradient");
      62             : }
      63             : 
      64             : }
      65             : 
      66             : #endif