Line data    Source code

       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             :    Copyright (c) 2016-2021 The VES code team
       3             :    (see the PEOPLE-VES file at the root of this folder for a list of names)
       4             : 
       5             :    See http://www.ves-code.org for more information.
       6             : 
       7             :    This file is part of VES code module.
       8             : 
       9             :    The VES code module 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             :    The VES code module 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 the VES code module.  If not, see <http://www.gnu.org/licenses/>.
      21             : +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
      22             : 
      23             : #include "TargetDistribution.h"
      24             : 
      25             : #include "core/ActionRegister.h"
      26             : 
      27             : 
      28             : namespace PLMD {
      29             : namespace ves {
      30             : 
      31             : //+PLUMEDOC VES_TARGETDIST TD_EXPONENTIAL
      32             : /*
      33             : Exponential distribution (static).
      34             : 
      35             : Employ a target distribution given by an
      36             : [exponential distribution](https://en.wikipedia.org/wiki/Exponential_distribution)
      37             : that is defined as
      38             : \f[
      39             : p(s) =
      40             : \lambda e^{-\lambda(s-a)}
      41             : \f]
      42             : where \f$a\f$ is the minimum of the distribution that is defined on the interval \f$[a,\infty)\f$,
      43             : and \f$\lambda>0\f$ is the so-called rate parameter.
      44             : 
      45             : The minimum \f$a\f$ is given using the MINIMUM keyword, and the rate parameter \f$\lambda\f$ is given
      46             : using the LAMBDA keyword.
      47             : 
      48             : This target distribution action is only defined for one dimension, for multiple dimensions
      49             : it should be used in combination with \ref TD_PRODUCT_DISTRIBUTION action.
      50             : 
      51             : \par Examples
      52             : 
      53             : Exponential distribution with \f$a=10.0\f$ and \f$\lambda=0.5\f$
      54             : \plumedfile
      55             : td: TD_EXPONENTIAL  MINIMUM=-10.0  LAMBDA=0.5
      56             : \endplumedfile
      57             : 
      58             : The exponential distribution is only defined for one dimension so for multiple
      59             : dimensions we have to use it in combination with the \ref TD_PRODUCT_DISTRIBUTION action as shown in
      60             : the following example where we have a uniform distribution for argument 1 and
      61             : and an exponential distribution for argument 2
      62             : \plumedfile
      63             : td_uni: TD_UNIFORM
      64             : 
      65             : td_exp: TD_EXPONENTIAL  MINIMUM=-10.0  LAMBDA=0.5
      66             : 
      67             : td_pd: TD_PRODUCT_DISTRIBUTION DISTRIBUTIONS=td_uni,td_exp
      68             : \endplumedfile
      69             : 
      70             : 
      71             : */
      72             : //+ENDPLUMEDOC
      73             : 
      74             : class TD_Exponential: public TargetDistribution {
      75             :   std::vector<double> minima_;
      76             :   std::vector<double> lambda_;
      77             : public:
      78             :   static void registerKeywords(Keywords&);
      79             :   explicit TD_Exponential(const ActionOptions& ao);
      80             :   double getValue(const std::vector<double>&) const override;
      81             : };
      82             : 
      83             : 
      84             : PLUMED_REGISTER_ACTION(TD_Exponential,"TD_EXPONENTIAL")
      85             : 
      86             : 
      87          10 : void TD_Exponential::registerKeywords(Keywords& keys) {
      88          10 :   TargetDistribution::registerKeywords(keys);
      89          20 :   keys.add("compulsory","MINIMUM","The minimum of the exponential distribution.");
      90          20 :   keys.add("compulsory","LAMBDA","The lambda parameter of the exponential distribution given as positive number.");
      91          10 :   keys.use("WELLTEMPERED_FACTOR");
      92          10 :   keys.use("SHIFT_TO_ZERO");
      93          10 :   keys.use("NORMALIZE");
      94          10 : }
      95             : 
      96             : 
      97           8 : TD_Exponential::TD_Exponential(const ActionOptions& ao):
      98             :   PLUMED_VES_TARGETDISTRIBUTION_INIT(ao),
      99          16 :   minima_(0),
     100           8 :   lambda_(0)
     101             : {
     102           8 :   parseVector("MINIMUM",minima_);
     103           8 :   parseVector("LAMBDA",lambda_);
     104          16 :   for(unsigned int k=0; k<lambda_.size(); k++) {
     105           8 :     if(lambda_[k] < 0.0) {plumed_merror(getName()+": the value given in LAMBDA should be positive.");}
     106             :   }
     107             : 
     108             : 
     109           8 :   setDimension(minima_.size());
     110           8 :   if(getDimension()>1) {plumed_merror(getName()+": only defined for one dimension, for multiple dimensions it should be used in combination with the TD_PRODUCT_DISTRIBUTION action.");}
     111           8 :   if(lambda_.size()!=getDimension()) {plumed_merror(getName()+": the LAMBDA keyword does not match the given dimension in MINIMUM");}
     112           8 :   checkRead();
     113           8 : }
     114             : 
     115             : 
     116        1308 : double TD_Exponential::getValue(const std::vector<double>& argument) const {
     117             :   double value = 1.0;
     118        2616 :   for(unsigned int k=0; k<argument.size(); k++) {
     119        1308 :     double arg = (argument[k]-minima_[k])*lambda_[k];
     120        1308 :     if(arg<0.0) {plumed_merror(getName()+": the exponential distribution is not defined for values less that ones given in MINIMUM");}
     121        1308 :     value *= lambda_[k]*exp(-arg);
     122             :   }
     123        1308 :   return value;
     124             : }
     125             : 
     126             : 
     127             : 
     128             : }
     129             : }