ga/evaluator.tcc

/**
 *  \file
 *  \remark This file is part of VITA.
 *
 *  \copyright Copyright (C) 2014-2017 EOS di Manlio Morini.
 *
 *  \license
 *  This Source Code Form is subject to the terms of the Mozilla Public
 *  License, v. 2.0. If a copy of the MPL was not distributed with this file,
 *  You can obtain one at http://mozilla.org/MPL/2.0/
 */
 
#if !defined(VITA_GA_EVALUATOR_H)
#  error "Don't include this file directly, include the specific .h instead"
#endif
 
#if !defined(VITA_GA_EVALUATOR_TCC)
#define      VITA_GA_EVALUATOR_TCC
 
///
/// GP-evaluators use datasets, GA-evaluators need functions to be maximized.
///
/// \param[in] f an objective function
///
template<class T, class F>
ga_evaluator<T, F>::ga_evaluator(F f) : f_(f)
{
  // The assertion `assert(f)` works with function pointers and non capturing
  // lambdas (which are implicitly convertible to function pointers) but
  // fails with capturing lambdas
  // (e.g. <http://stackoverflow.com/q/7852101/3235496>).
}
 
///
/// \param[in] f objective function
/// \return      an evaluator based on `f`
///
/// This is the so called object generator idiom. Here it's used because C++11
/// standard doesn't allow for template argument deduction from the parameters
/// passed to the constructor.
///
/// Any reasonable compiler will optimize away the temporary object and this
/// is usually faster than a solution based on `std::function`.
///
/// \see
/// * <http://stackoverflow.com/q/984394/3235496>
/// * <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3602.html>
///
template<class T, class F>
ga_evaluator<T, F> make_ga_evaluator(F f)
{
  return ga_evaluator<T, F>(f);
}
 
///
/// \return the fitness of the individual
///
template<class T, class F>
fitness_t ga_evaluator<T, F>::operator()(const T &ind)
{
  const auto f_v(f_(ind));
 
  using std::isfinite;
  if (isfinite(f_v))
    return {f_v};
 
  return {};
}
#endif  // include guard