libevocosm-dev 4.0.2-3ubuntu2 / usr / include / libevocosm / evoreal.h

/*
    Evocosm is a C++ framework for implementing evolutionary algorithms.

    Copyright 2011 Scott Robert Ladd. All rights reserved.

    Evocosm is user-supported open source software. Its continued development is dependent
    on financial support from the community. You can provide funding by visiting the Evocosm
    website at:

        http://www.coyotegulch.com

    You may license Evocosm in one of two fashions:

    1) Simplified BSD License (FreeBSD License)

    Redistribution and use in source and binary forms, with or without modification, are
    permitted provided that the following conditions are met:

    1.  Redistributions of source code must retain the above copyright notice, this list of
        conditions and the following disclaimer.

    2.  Redistributions in binary form must reproduce the above copyright notice, this list
        of conditions and the following disclaimer in the documentation and/or other materials
        provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY SCOTT ROBERT LADD ``AS IS'' AND ANY EXPRESS OR IMPLIED
    WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
    FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SCOTT ROBERT LADD OR
    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
    ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
    ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    The views and conclusions contained in the software and documentation are those of the
    authors and should not be interpreted as representing official policies, either expressed
    or implied, of Scott Robert Ladd.

    2) Closed-Source Proprietary License

    If your project is a closed-source or proprietary project, the Simplified BSD License may
    not be appropriate or desirable. In such cases, contact the Evocosm copyright holder to
    arrange your purchase of an appropriate license.

    The author can be contacted at:

          scott.ladd@coyotegulch.com
          scott.ladd@gmail.com
          http:www.coyotegulch.com
*/

#if !defined(LIBEVOCOSM_EVOREAL_H)
#define LIBEVOCOSM_EVOREAL_H

// libevocosm
#include "evocommon.h"

namespace libevocosm
{
    //! Tools for evolving real numbers
    /*!
        The majority of genetic algorithms work on pure bit strings, converting
        those strings to the desired types for fitness testing. In Lawrence
        Davis' book "Handbook of Genetic Algorithms," he transforms a 44-bit
        string into two floating point values via a series of operations. I've
        seen similar techniques elsewhere, and I find them a bit cumbersome.
        <p>
        In the purest sense, a GA should have no knowledge of the format of the
        data it is modifying; however, natural chromosomes do encode some
        structure in their sequence; for example, crossover appears to take place
        in specific positions along the chromosome. And while mutation doesn't
        care about a chromosome's structure, it does affect that structure.
        In context of a computer program, the structure of a chromosome isn't
        so important as the ability to logically modify its bits through
        crossover and mutation.
        <p>
        I built tools for the mutation and crossover of encoded floating-point
        values of types <b>float</b> and <b>double</b>. The code that follows
        assumes we are working with 32-bit floats and 64-bit IEEE-754 doubles,
        which, in my experience, the norm for many C and C++ compilers. Yes,
        I'm aware of the VAX and other systems; this code is explicitly
        non-portable outside implementations of IEC 60559/IEEE-754.
    */
    class evoreal : protected globals
    {
    public:
        //! Creation constructor
        /*!
            Creates a new evoreal object based on a set of  weights that define
            the chance of mutation in various components of a floating-point value.
            The default weights have worked well in a variety of applications, but
            are (of course) settable for specific application and experimentation.
            <p>
            Each weight is a percentage of the total of all three weights; for
            example, if the three weights add to 100 (as they do by efault), and
            a_sign_weight is 12, the chance of a mutation in the sign bit is 12%.
            The default weights were chosen based on experience in using these
            tools in a variety of applications.
            \param a_sign_weight - Weight assigned to changes in sign
            \param a_exponent_weight - Weight assigned to changes in the exponent
            \param a_mantissa_weight - Weight assigned to changes in the mantissa
        */
        evoreal(float a_sign_weight = 5.0F, float a_exponent_weight =  5.0F, float a_mantissa_weight = 90.0F);

        //! Copy constructor
        /*!
            Creates a new evoreal with the same states as an existing one.
            \param a_source - The source object
        */
        evoreal(evoreal & a_source);

        //! Assignment
        /*!
            Assigns the state of one evoreal to another.
            \param a_source - The source object
        */
        evoreal & operator = (evoreal & a_source);

        //! Mutation for <b>float</b> values
        /*!
            Returns a new float that is a mutated version of the argument.
            \param a_f - Number to be cloned; the result is then mutated
            \return A clone of a_f that has bene mutated
        */
        float  mutate(float  a_f);

        //! Mutation for <b>double</b> values
        /*!
            Returns a new float that is a mutated version of the argument.
            \param a_d - Number to be cloned; the result is then mutated
            \return A clone of a_d that has bene mutated
        */
        double mutate(double a_d);

        //! Crossover for <b>float</b> values
        /*!
            Creates a new float by combining two values through a
            real-specialized form of crossover.
            \param a_f1 - First parent number
            \param a_f2 - Second parent number
            \return A combination of the two arguments
        */
        float crossover(float  a_f1, float  a_f2);

        //! Crossover for <b>double</b> values
        /*!
            Creates a new double by combining two values through a
            real-specialized form of crossover.
            \param a_d1 - First parent number
            \param a_d2 - Second parent number
            \return A combination of the two arguments
        */
        double crossover(double a_d1, double a_d2);

    private:
        // weights used to select parts of a number for manipulation
        const float m_total_weight;
        const float m_sign_weight;
        const float m_exp_weight;

#if defined(_MSC_VER) && (_MSC_VER < 1300)
        static const long FLT_EXP_BITS;
        static const long DBL_EXP_BITS;
#else
        static const long FLT_EXP_BITS = 0x7F800000L;
        static const long DBL_EXP_BITS = 0x7FF00000UL;
#endif
    };
}

#endif