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             : #include "core/ActionShortcut.h"
      23             : #include "core/ActionRegister.h"
      24             : 
      25             : //+PLUMEDOC ANALYSIS LOGSUMEXP
      26             : /*
      27             : This action takes the exponential of a vector of logarithms and divides each element of the vector by the sum of the exponentials.
      28             : 
      29             : The log-exp-sum trick is used here
      30             : 
      31             : \par Examples
      32             : 
      33             : */
      34             : //+ENDPLUMEDOC
      35             : 
      36             : namespace PLMD {
      37             : namespace landmarks {
      38             : 
      39             : class LogSumExp : public ActionShortcut {
      40             : private:
      41             :   std::string fixArgumentName( const std::string& argin );
      42             : public:
      43             :   static void registerKeywords( Keywords& keys );
      44             :   explicit LogSumExp( const ActionOptions& ao );
      45             : };
      46             : 
      47             : PLUMED_REGISTER_ACTION(LogSumExp,"LOGSUMEXP")
      48             : 
      49          20 : void LogSumExp::registerKeywords( Keywords& keys ) {
      50          20 :   ActionShortcut::registerKeywords( keys );
      51          40 :   keys.add("compulsory","ARG","the vector of logweights that you would like to normalise using the logsumexp trick");
      52          20 :   keys.setValueDescription("the logarithms of the input weights logweights that are computed with the log-sum weights formula");
      53          60 :   keys.needsAction("HIGHEST"); keys.needsAction("CUSTOM"); keys.needsAction("SUM");
      54          20 : }
      55             : 
      56             : 
      57           9 : LogSumExp::LogSumExp( const ActionOptions& ao ):
      58             :   Action(ao),
      59           9 :   ActionShortcut(ao)
      60             : {
      61             :   // Find the argument name
      62           9 :   std::string argn; parse("ARG",argn);
      63             :   // Find the maximum weight
      64          18 :   readInputLine( getShortcutLabel() + "_maxlogweight: HIGHEST ARG=" + argn );
      65          18 :   readInputLine( getShortcutLabel() + "_maxweight: CUSTOM ARG=" + getShortcutLabel() + "_maxlogweight FUNC=exp(x) PERIODIC=NO");
      66             :   // Calculate the maximum
      67          18 :   readInputLine( getShortcutLabel() + "_shiftw: CUSTOM ARG=" + argn + "," + getShortcutLabel() + "_maxlogweight FUNC=exp(x-y) PERIODIC=NO");
      68             :   // compute the sum of all the exponentials
      69          18 :   readInputLine( getShortcutLabel() + "_sumw: SUM ARG=" + getShortcutLabel() + "_shiftw PERIODIC=NO");
      70             :   // and the logsum
      71          18 :   readInputLine( getShortcutLabel() + "_logsum: CUSTOM ARG=" + getShortcutLabel() + "_sumw," + getShortcutLabel() + "_maxlogweight FUNC=y+log(x) PERIODIC=NO");
      72             :   // And the final weights
      73          18 :   readInputLine( getShortcutLabel() + ": CUSTOM ARG=" + argn + "," +  getShortcutLabel() + "_logsum FUNC=exp(x-y) PERIODIC=NO");
      74           9 : }
      75             : 
      76             : }
      77             : }