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eo/src/utils/eoHowMany.h

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+// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-
+
+//-----------------------------------------------------------------------------
+// eoHowMany_h.h
+//   Base class for choosing a number of guys to apply something from a popsize
+// (c) Marc Schoenauer, 2000
+// (c) Thales group, 2010 (Johann Dréo <johann.dreo@thalesgroup.com>)
+
+/*
+   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: http://eodev.sourceforge.net
+
+*/
+//-----------------------------------------------------------------------------
+
+#ifndef eoHowMany_h
+#define eoHowMany_h
+
+#include <sstream>
+
+#include <utils/eoLogger.h>
+
+
+/** A helper class, to determine a number of individuals from another one
+ *  Typically, is used in selection / replacement procedures, e.g.
+ *             the number of offspring from the number of parents, or
+ *             the number of survivors for an eoReduce functor, ...
+ *
+ * Such construct is very useful because in some cases you might not know the
+ * population size that will enter the replacement. For instance, you
+ * cannot simply have a pre-computed (double) rate of 1/popSize
+ * if you want to select or kill just 1 guy. Using an eoHowMany
+ * allows one to modify the population size without touching anything else.
+ *
+ * There are 4 possible way to compute the return value from the argument:
+ *    - an absolute POSITIVE integer  --> return it (regardless of popsize)
+ *    - a POSITIVE rate               -->  return rate*popSize
+ *    - an absolute NEGATIVE integer  --> return popsize-rate (if positive)
+ *    - a NEGATIVE rate in [-1,0]     --> store and use 1-|rate| (positive)
+ * Note that a negative rate should be have been necessary because a rate is
+ * relative, but it is there for consistency reasons - and because it
+ * is needed in <a href="classeo_g3_replacement_h-source.html">eoG3Replacement</a>
+ *
+ * It has 2 private members, a double and an integer to cover all cases
+ *
+ * Example use: in <a href="class_eogeneralbreeder.html">eoGeneralBreeder.h</a>
+ * Example reading from parser: in
+ *         <a href="make_algo_scalar_h-source.html">do/make_algo_scalar.h line 141</a>
+
+ * MS 10/04/2002:
+ *    Added the possibility to have a negative number -
+ *        when treated as a number: returns then (size - count)
+ *    Should not modify anything when a positive number is passed in the ctor
+ *
+ * MS 20/06/2002:
+ *    Added the negative rate and the operator-() (for
+ *    eoG3Repalcement)
+ *
+ * It is an eoPersistent because we need to be able to use eoParamValue<eoHowMany>
+ *
+ * @ingroup Core
+ */
+class eoHowMany : public eoPersistent
+{
+public:
+  /** Original Ctor from direct rate + bool
+      @param _rate    the rate, OR the integer to store, depending on 2nd arg.
+      @param _interpret_as_rate to tell whether the rate actually is a rate
+  */
+  eoHowMany(double  _rate = 0.0, bool _interpret_as_rate = true):
+    rate(_rate), count(0)
+  {
+    if (_interpret_as_rate)
+      {
+        if (_rate<0)
+          {
+            rate = 1.0+_rate;
+            if (rate < 0)           // was < -1
+              throw std::logic_error("rate<-1 in eoHowMany!");
+          }
+      }
+    else
+      {
+        rate = 0.0;                   // just in case, but shoud be unused
+        count = int(_rate);           // negative values are allowed here
+        if (count != _rate)
+          eo::log << eo::warnings << "Number was rounded in eoHowMany";
+      }
+  }
+
+  /** Ctor from an int - both from int and unsigned int are needed
+   *     to avoid ambiguity with the Ctor from a double */
+  eoHowMany(int _count) : rate(0.0), count(_count) {}
+
+  /** Ctor from an unsigned int - both from int and unsigned int are needed
+   *     to avoid ambiguity with the Ctor from a double */
+  eoHowMany(unsigned int _count) : rate(0.0), count(_count) {}
+
+  /// Virtual dtor. They are needed in virtual class hierarchies.
+  virtual ~eoHowMany() {}
+
+  /** Does what it was designed for
+   *  - count==0 : return rate*_size
+   *  - else
+   *    - count>0 : return count (regardless of _size)
+   *    - count<0 : return _size-|count|
+   */
+  unsigned int operator()(unsigned int _size)
+  {
+    if (count == 0)
+      {
+        unsigned int res = static_cast<unsigned int>( std::ceil( rate * _size ) );
+
+        if( res == 0 ) {
+            eo::log << eo::warnings << "Call to a eoHowMany instance returns 0 (rate=" << rate << ", size=" << _size << ")" << std::endl;
+        }
+
+        return res;
+      }
+    if (count < 0)
+      {
+        unsigned int combloc = -count;
+        if (_size<combloc)
+          throw std::runtime_error("Negative result in eoHowMany");
+        return _size-combloc;
+      }
+    return unsigned(count);
+  }
+
+  virtual void printOn(std::ostream& _os) const
+  {
+    if (count == 0)
+      _os << 100*rate << "% ";
+    else
+      _os << count << " ";
+    return;
+
+  }
+
+  virtual void readFrom(std::istream& _is)
+   {
+    std::string value;
+    _is >> value;
+    readFrom(value);
+    return;
+  }
+
+  void readFrom(std::string _value)
+  {
+    // check for %
+    bool interpret_as_rate = false;   // == no %
+    size_t pos =  _value.find('%');
+    if (pos < _value.size())  //  found a %
+      {
+        interpret_as_rate = true;
+        _value.resize(pos);           // get rid of %
+      }
+
+    std::istringstream is(_value);
+    is >> rate;
+    // now store
+    if (interpret_as_rate)
+      {
+        count = 0;
+        rate /= 100.0;
+      }
+    else
+      count = int(rate);           // and rate will not be used
+
+    // minimal check
+    if ( rate < 0.0 )
+      throw std::runtime_error("Negative rate read in eoHowMany::readFrom");
+  }
+
+  /** The unary - operator: reverses the computation */
+  eoHowMany operator-()
+  {
+    if (!count)                   // only rate is used
+      rate = 1.0-rate;
+    else
+      count = -count;
+    return (*this);
+  }
+
+private :
+  double rate;
+  int count;
+};
+
+
+
+#endif