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eo/src/eoParetoFitness.h

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+// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-
+
+//-----------------------------------------------------------------------------
+// eoParetoFitness.h
+// (c) Maarten Keijzer and Marc Schoenauer, 2001
+/*
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+    Contact: mak@dhi.dk
+             Marc.Schoenauer@polytechnique.fr
+ */
+//-----------------------------------------------------------------------------
+
+#ifndef _eoParetoFitness_h
+#define _eoParetoFitness_h
+
+#include <vector>
+
+/**
+  eoFitnessTraits: a traits class to specify the number of objectives and which one are maximizing
+  or not. See eoParetoFitness for its use. If you define your own, make sure you make the functions
+  static!
+*/
+class eoParetoFitnessTraits
+{
+  public :
+
+  static unsigned nObjectives()          { return 2; }
+  static double tol()               { return 1e-6; }
+  static bool maximizing(int which) { return true; } // by default: all are maximizing
+};
+
+/**
+  eoParetoFitness class: vector of doubles with overloaded comparison operators. Comparison is done
+  on pareto dominance. The template argument FitnessTraits defaults to eoParetoFitnessTraits, which
+  can be replaces at will by any other class that implements the static functions defined therein.
+
+  Note that the comparison defines a partial order, so that
+    !(a < b) && !(b <a) does not neccessarily imply that (a==b)
+  The other way around does hold.
+*/
+template <class FitnessTraits = eoParetoFitnessTraits>
+class eoParetoFitness : public std::vector<double>
+{
+public :
+
+  eoParetoFitness(void) : std::vector<double>(FitnessTraits::nObjectives(),0.0) {}
+
+  /// Partial order based on Pareto-dominance
+  bool operator<(const eoParetoFitness<FitnessTraits>& _other) const
+  {
+    bool smaller = false;
+    double tol = FitnessTraits::tol();
+    const vector<double>& performance = *this;
+    const vector<double>& otherperformance = _other;
+
+    for (unsigned i = 0; i < FitnessTraits::nObjectives(); ++i)
+    {
+      bool maxim = FitnessTraits::maximizing(i);
+      double aval = maxim? performance[i] : -performance[i];
+      double bval = maxim? otherperformance[i] : otherperformance[i];
+
+      if (fabs(aval - bval) > tol)
+      {
+        if (aval > bval)
+        {
+          return false; // cannot dominate
+        }
+        // else aval < bval
+        smaller = true; // goto next objective
+      }
+      //else they're equal in this objective, goto next
+    }
+
+    return smaller;
+  }
+
+  bool operator>(const eoParetoFitness<FitnessTraits>& _other) const
+  {
+    return _other < *this;
+  }
+
+  bool operator<=(const eoParetoFitness<FitnessTraits>& _other) const
+  {
+    return operator==(_other) || operator<(_other);
+  }
+
+  bool operator>=(const eoParetoFitness<FitnessTraits>& _other) const
+  {
+    return _other <= *this;
+  }
+
+  bool operator==(const eoParetoFitness<FitnessTraits>& _other) const
+  { // check if they're all within tolerance
+    for (unsigned i = 0; i < size(); ++i)
+    {
+      if (fabs(operator[](i) - _other[i]) > FitnessTraits::tol())
+      {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  bool operator!=(const eoParetoFitness<FitnessTraits>& _other) const
+  { return ! operator==(_other); }
+
+};
+
+template <class FitnessTraits>
+std::ostream& operator<<(std::ostream& os, const eoParetoFitness<FitnessTraits>& fitness)
+{
+  for (unsigned i = 0; i < fitness.size(); ++i)
+  {
+    os << fitness[i] << ' ';
+  }
+  return os;
+}
+
+template <class FitnessTraits>
+std::istream& operator>>(std::istream& is, eoParetoFitness<FitnessTraits>& fitness)
+{
+  fitness = eoParetoFitness<FitnessTraits>();
+  for (unsigned i = 0; i < fitness.size(); ++i)
+  {
+    is >> fitness[i];
+  }
+  return is;
+}
+
+#endif