/usr/include/libevocosm/selector.h is in libevocosm-dev 3.1.0-3.1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// Algorithmic Conjurings @ http://www.coyotegulch.com
// Evocosm -- An Object-Oriented Framework for Evolutionary Algorithms
//
// selector.h
//---------------------------------------------------------------------
//
// Copyright 1996, 1999, 2002, 2003, 2004, 2005 Scott Robert Ladd
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the
// Free Software Foundation, Inc.
// 59 Temple Place - Suite 330
// Boston, MA 02111-1307, USA.
//
//-----------------------------------------------------------------------
//
// For more information on this software package, please visit
// Scott's web site, Coyote Gulch Productions, at:
//
// http://www.coyotegulch.com
//
//-----------------------------------------------------------------------
#if !defined(EVOCOSM_SELECTOR_H)
#define EVOCOSM_SELECTOR_H
// Standard C++ Library
#include <algorithm>
// libevocosm
#include "organism.h"
namespace libevocosm
{
//! Selects organisms that survive
/*!
A selector decides which organisms survive from one generation to the
next. Some evolutionary algorithms will not use a selector; others will.
In general, it is effective to keep the "best" organisms from one
generation ot the next, so that good genes do not become lost at
random.
<p>
Of course, "real" nature isn't so kind; just because you're the
biggest stag in the forest doesn't mean you won't get shot! In fact,
that may say something about the "best" -- maybe the "best" stag is
the one that is too ugly for anyone to hunt?
\param OrganismType - The type of organism being selected
*/
template <class OrganismType>
class selector : protected globals
{
public:
//! Virtual destructor
/*!
A virtual destructor. By default, it does nothing; this is
a placeholder that identifies this class as a potential base,
ensuring that objects of a derived class will have their
destructors called if they are destroyed through a base-class
pointer.
*/
virtual ~selector()
{
// nada
}
//! Select individuals that survive
/*!
Produces a vector containing copies of the organisms selected for
survival.
\param a_population - A population of organisms
\return A population of copied survivors
*/
virtual vector<OrganismType> select_survivors(vector<OrganismType> & a_population) = 0;
};
//! A do-nothing selector
/*!
The null_selector doesn't select anything; it's just a placeholder used
in evolutionary algorithms that do not use survival.
\param OrganismType - The type of organism
*/
template <class OrganismType>
class null_selector : public selector<OrganismType>
{
public:
// Do-nothing selection function
/*!
Has no effect on the target population.
\param a_population - A population of organisms
*/
virtual vector<OrganismType> select_survivors(vector<OrganismType> & a_population)
{
return vector<OrganismType>(); // an empty vector
}
};
//! Implements a elitism selector
/*!
Elitism is one of the simplest type of selection -- it simply says that
the <i>n</i> best organisms will survive into the next generation.
\param OrganismType - The type of organism
*/
template <class OrganismType>
class elitism_selector : public selector<OrganismType>
{
public:
//! Constructor
/*!
Constructs a new elistism_selector with a value that defines the number of
organisms that should survive into the next generation.
\param a_how_many - The maximum number of survivors
*/
elitism_selector(size_t a_how_many = 1)
: m_how_many(a_how_many)
{
// nada
}
//! Copy constructor
/*!
Creates a new object identical to an existing one.
\param a_source - The source object
*/
elitism_selector(const elitism_selector<OrganismType> & a_source)
: m_how_many(a_source.how_many)
{
// nada
}
//! Assignment operator
/*!
Assigns an existing object the state of another.
\param a_source - The source object
*/
elitism_selector & operator = (const elitism_selector<OrganismType> & a_source)
{
m_how_many = a_source.m_how_many;
}
//! Select individuals that survive
/*!
Produces a vector containing copies of the organisms selected for
survival.
\param a_population - A population of organisms
\return A population of copied survivors
*/
virtual vector<OrganismType> select_survivors(vector<OrganismType> & a_population);
private:
// number of organisms to keep
size_t m_how_many;
};
template <class OrganismType>
vector<OrganismType> elitism_selector<OrganismType>::select_survivors(vector<OrganismType> & a_population)
{
// create a new vector
vector<OrganismType> chosen_ones;
if (m_how_many > 0)
{
for (typename vector<OrganismType>::iterator i = a_population.begin(); i != a_population.end(); ++i)
{
typename vector<OrganismType>::iterator c = chosen_ones.begin();
size_t n = 0;
while ((c != chosen_ones.end()) && (n < m_how_many))
{
if (i->fitness() > c->fitness())
break;
++c;
++n;
}
if (n < m_how_many)
chosen_ones.insert(c,*i);
if (chosen_ones.size() > m_how_many)
chosen_ones.pop_back();
}
}
// return result
return chosen_ones;
}
};
#endif
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