Line data    Source code

       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             :    Copyright (c) 2011-2023 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_SwitchingFunction_h
      23             : #define __PLUMED_tools_SwitchingFunction_h
      24             : 
      25             : #include <string>
      26             : #include <vector>
      27             : #include <memory>
      28             : #include "lepton/Lepton.h"
      29             : 
      30             : namespace PLMD {
      31             : 
      32             : class Log;
      33             : class Keywords;
      34             : namespace switchContainers {
      35             : /// container for the actual switching function used by PLMD::SwitchingFunction
      36             : class baseSwitch {
      37             : protected:
      38             :   /// Minimum distance (before this, function is one)
      39             :   double d0=0.0;
      40             :   /// Maximum distance (after this, function is zero)
      41             :   double dmax=0.0;
      42             :   /// Square of dmax, useful in calculateSqr()
      43             :   double dmax_2=0.0;
      44             :   /// We store the inverse to avoid a division
      45             :   double invr0=0.0;
      46             :   /// Square of invr0, useful in calculateSqr()
      47             :   double invr0_2=0.0;
      48             :   /// Parameters for stretching the function to zero at d_max
      49             :   double stretch=1.0;
      50             :   double shift=0.0;
      51             :   std::string mytype;
      52             :   virtual std::string specificDescription() const;
      53             :   //
      54             :   virtual double function(double rdist, double& dfunc) const=0;
      55             : public:
      56             :   baseSwitch(double D0,double DMAX, double R0, std::string_view name);
      57             :   virtual ~baseSwitch();
      58             :   ///the driver for the function (prepares rdist or returns 1 or 0 automatically)
      59             :   virtual double calculate(double distance, double& dfunc) const;
      60             :   virtual double calculateSqr(double distance2, double& dfunc) const;
      61             :   void setupStretch();
      62             :   void removeStretch();
      63             :   std::string description() const;
      64             :   double get_d0() const;
      65             :   double get_r0() const;
      66             :   double get_dmax() const;
      67             :   double get_dmax2() const;
      68             : };
      69             : } // namespace switchContainers
      70             : 
      71             : /// \ingroup TOOLBOX
      72             : /// Small class to compute switching functions.
      73             : /// Switching functions are created using set() and
      74             : /// then can be used with function calculate() or calculateSqr().
      75             : /// Since this is typically computed on a distance vector,
      76             : /// the second all (calculateSqr()) allows to skip the calculation
      77             : /// of a square root in some case, thus potentially increasing
      78             : /// performances.
      79        2687 : class SwitchingFunction {
      80             : /// This is to check that switching function has been initialized
      81             :   bool init=false;
      82             :   std::unique_ptr<switchContainers::baseSwitch> function;
      83             : public:
      84             :   static void registerKeywords( Keywords& keys );
      85             : /// Set a "rational" switching function.
      86             : /// Notice that a d_max is set automatically to a value such that
      87             : /// f(d_max)=0.00001.
      88             :   void set(int nn,int mm,double r_0,double d_0);
      89             : /// Set an arbitrary switching function.
      90             : /// Parse the string in definition and possibly returns errors
      91             : /// in the errormsg string
      92             :   void set(const std::string& definition, std::string& errormsg);
      93             : /// Returns a string with a description of the switching function
      94             :   std::string description() const ;
      95             : /// Compute the switching function.
      96             : /// Returns s(x). df will be set to the value of the derivative
      97             : /// of the switching function _divided_by_x
      98             :   double calculate(double x,double&df)const;
      99             : /// Compute the switching function.
     100             : /// Returns \f$ s(\sqrt{x})\f$ .
     101             : /// df will be set to the \f$ \frac{1}{\sqrt{x}}\frac{ds}{d\sqrt{x}}= 2 \frac{ds}{dx}\f$
     102             : /// (same as calculate()).
     103             : /// The advantage is that in some case the expensive square root can be avoided
     104             : /// (namely for rational functions, if nn and mm are even and d0 is zero)
     105             :   double calculateSqr(double distance2,double&dfunc)const;
     106             : /// Returns d0
     107             :   double get_d0() const;
     108             : /// Returns r0
     109             :   double get_r0() const;
     110             : /// Return dmax
     111             :   double get_dmax() const;
     112             : /// Return dmax squared
     113             :   double get_dmax2() const;
     114             : };
     115             : 
     116             : } //namespace PLMD
     117             : 
     118             : #endif