Line data    Source code

       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             :    Copyright (c) 2014-2023 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/ActionRegister.h"
      23             : #include "core/ActionShortcut.h"
      24             : #include "core/ActionWithArguments.h"
      25             : #include "core/PlumedMain.h"
      26             : #include "FunctionSetup.h"
      27             : #include "FunctionOfScalar.h"
      28             : #include "FunctionWithSingleArgument.h"
      29             : 
      30             : //+PLUMEDOC FUNCTION PRODUCT
      31             : /*
      32             : Calculate the product of the input quantities
      33             : 
      34             : This shortcut can be used to calculate the product of a collection of scalar inputs as illustrated by the following
      35             : simple example.
      36             : 
      37             : ```plumed
      38             : d1: DISTANCE ATOMS=1,2
      39             : d2: DISTANCE ATOMS=3,4
      40             : p: PRODUCT ARG=d1,d2
      41             : ```
      42             : 
      43             : You can also calculate the product of all the elements of a vector:
      44             : 
      45             : ```plumed
      46             : d: DISTANCE ATOMS1=1,2 ATOMS2=3,4 ATOMS3=5,6
      47             : p: PRODUCT ARG=d
      48             : ```
      49             : 
      50             : The product is computed directly, so the input values can be negative or zero. The derivative with respect to
      51             : each input is the product of all the other inputs.
      52             : 
      53             : This action is used in the [DETERMINANT](DETERMINANT.md) shortcut. In that
      54             : action the determinant of the input square matrix is found by finding the eigenvalues of the
      55             : input matrix using [DIAGONALIZE](DIAGONALIZE.md). The determinant is then found by evaluating
      56             : the product of these eigenvalues.
      57             : 
      58             : */
      59             : //+ENDPLUMEDOC
      60             : 
      61             : namespace PLMD {
      62             : namespace function {
      63             : 
      64             : class ProductFunction {
      65             : public:
      66             :   static void registerKeywords( Keywords& keys );
      67             :   static void read( ProductFunction& func, ActionWithArguments* action, FunctionOptions& options );
      68             :   static void calc( const ProductFunction& func, bool noderiv, View<const double> args, FunctionOutput& funcout );
      69             : };
      70             : 
      71             : typedef FunctionOfScalar<ProductFunction> ScalarProduct;
      72             : PLUMED_REGISTER_ACTION(ScalarProduct,"PRODUCT_SCALAR")
      73             : typedef FunctionWithSingleArgument<ProductFunction> OneargProduct;
      74             : PLUMED_REGISTER_ACTION(OneargProduct,"PRODUCT_ONEARG")
      75             : 
      76          32 : void ProductFunction::registerKeywords( Keywords& keys ) {
      77          64 :   keys.setValueDescription("scalar","the product of the input values");
      78          32 : }
      79             : 
      80          12 : void ProductFunction::read( ProductFunction& func, ActionWithArguments* action, FunctionOptions& options ) {
      81          29 :   for(unsigned i=0; i<action->getNumberOfArguments(); ++i) {
      82          17 :     if( action->getPntrToArgument(i)->getRank()>1 ) {
      83           0 :       action->error("the product of the elements of a matrix is not implemented");
      84             :     }
      85             :   }
      86          12 : }
      87             : 
      88          24 : void ProductFunction::calc( const ProductFunction& func, bool noderiv, const View<const double> args, FunctionOutput& funcout ) {
      89             :   const std::size_t n=args.size();
      90             :   double prod=1.0;
      91          90 :   for(std::size_t i=0; i<n; ++i) {
      92          66 :     prod *= args[i];
      93             :   }
      94          24 :   funcout.values[0]=prod;
      95          24 :   if( noderiv ) {
      96             :     return;
      97             :   }
      98             :   // d prod / d x_i is the product of all the other inputs: it is computed
      99             :   // with a forward and a backward pass, without dividing by x_i, so zeros are fine
     100             :   double left=1.0;
     101          65 :   for(std::size_t i=0; i<n; ++i) {
     102          50 :     funcout.derivs[0][i]=left;
     103          50 :     left *= args[i];
     104             :   }
     105             :   double right=1.0;
     106          65 :   for(std::size_t i=n; i>0; --i) {
     107          50 :     funcout.derivs[0][i-1] *= right;
     108          50 :     right *= args[i-1];
     109             :   }
     110             : }
     111             : 
     112             : class Product : public ActionShortcut {
     113             : public:
     114             :   static void registerKeywords( Keywords& keys );
     115             :   explicit Product(const ActionOptions&ao);
     116             : };
     117             : 
     118             : PLUMED_REGISTER_ACTION(Product,"PRODUCT")
     119             : 
     120          26 : void Product::registerKeywords( Keywords& keys ) {
     121          26 :   ActionShortcut::registerKeywords(keys);
     122          52 :   keys.addInputKeyword("compulsory","ARG","scalar/vector","the scalars (or the vector) whose elements you would like to multiply together");
     123          52 :   keys.setValueDescription("scalar","the product of all the input values");
     124          26 :   keys.addActionNameSuffix("_SCALAR");
     125          26 :   keys.addActionNameSuffix("_ONEARG");
     126          26 :   keys.needsAction("CONCATENATE");
     127          26 : }
     128             : 
     129          12 : Product::Product( const ActionOptions& ao):
     130             :   Action(ao),
     131          12 :   ActionShortcut(ao) {
     132          12 :   std::vector<std::string> args;
     133          24 :   parseVector("ARG",args);
     134          12 :   if( args.empty() ) {
     135           0 :     error("no arguments specified");
     136             :   }
     137          12 :   std::vector<Value*> vals;
     138          12 :   ActionWithArguments::interpretArgumentList( args, plumed.getActionSet(), this, vals );
     139          12 :   if( vals.empty() ) {
     140           0 :     error("found no input arguments to product");
     141             :   }
     142          12 :   std::string allargs=args[0];
     143          14 :   for(unsigned i=1; i<args.size(); ++i) {
     144           4 :     allargs += "," + args[i];
     145             :   }
     146             :   bool allscalars=true;
     147          29 :   for(const auto & v : vals) {
     148          17 :     if( v->getRank()>1 || (v->getRank()>0 && v->hasDerivatives()) ) {
     149           0 :       error("PRODUCT only accepts scalars and vectors in input");
     150             :     }
     151          17 :     if( v->getRank()!=0 ) {
     152             :       allscalars=false;
     153             :     }
     154             :   }
     155          12 :   if( allscalars ) {
     156           8 :     readInputLine( getShortcutLabel() + ": PRODUCT_SCALAR ARG=" + allargs );
     157           8 :   } else if( vals.size()==1 ) {
     158          16 :     readInputLine( getShortcutLabel() + ": PRODUCT_ONEARG ARG=" + allargs );
     159             :   } else {
     160           0 :     readInputLine( getShortcutLabel() + "_vec: CONCATENATE ARG=" + allargs );
     161           0 :     readInputLine( getShortcutLabel() + ": PRODUCT_ONEARG ARG=" + getShortcutLabel() + "_vec" );
     162             :   }
     163          12 : }
     164             : 
     165             : }
     166             : }