ex2.c

遗传算法求解优化问题

/* ----------------------------------------------------------------------------
  ex2.C
  mbwall 28jul94
  Copyright (c) 1995-1996  Massachusetts Institute of Technology

 DESCRIPTION:
   Example program for the SimpleGA class and Bin2DecGenome class.  This
program generates randomly a series of numbers then tries to match those
values in a binary-to-decimal genome.  We use a simple GA (with linear
scaled fitness selection and non-steady-state population generation) and
binary-to-decimal, 1D genomes.  We also use the userData argument to the
objective function.
---------------------------------------------------------------------------- */
#include <stdio.h>
#include <iostream.h>
#include <fstream.h>
#include <math.h>

#include <ga/GASimpleGA.h>
#include <ga/GABin2DecGenome.h>

float Objective(GAGenome &);

int
main(int argc, char **argv)
{
  cout << "Example 2\n\n";
  cout << "This program generates a sequence of random numbers then uses\n";
  cout << "a simple GA and binary-to-decimal genome to match the\n";
  cout << "sequence.\n\n";

// See if we've been given a seed to use (for testing purposes).  When you
// specify a random seed, the evolution will be exactly the same each time
// you use that seed number.

  unsigned int seed = 0;
  for(int ii=1; ii<argc; ii++) {
    if(strcmp(argv[ii++],"seed") == 0) {
      seed = atoi(argv[ii]);
    }
  }

// Declare variables for the GA parameters and set them to some default values.

  int popsize  = 25;
  int ngen     = 100;
  float pmut   = 0.01;
  float pcross = 0.6;

// Generate a sequence of random numbers using the values in the min and max
// arrays.  We also set one of them to integer value to show how you can get
// explicit integer representations by choosing your number of bits
// appropriately.

  GARandomSeed(seed);
  int n=7;
  float *target = new float[n];
  float min[] = {0, 0,   3, -5, 100,    0.001, 0};
  float max[] = {1, 100, 3, -2, 100000, 0.010, 7};
  int i;
  for(i=0; i<n; i++)
    target[i] = GARandomFloat(min[i], max[i]);
  target[6] = GARandomInt((int)min[6], (int)max[6]);

// Print out the sequence to see what we got.

  cout << "input sequence:\n";
  for(i=0; i<n; i++){
    cout.width(10);
    cout << target[i] << " ";
  }
  cout << "\n"; cout.flush();

// Create a phenotype then fill it with the phenotypes we will need to map to
// the values we read from the file.  The arguments to the add() method of a
// Bin2Dec phenotype are (1) number of bits, (2) min value, and (3) max value.
// The phenotype maps a floating-point number onto the number of bits that
// you designate.  Here we just make everything use 8 bits and use the max and
// min that were used to generate the target values.  You can experiment with
// the number of bits and max/min values in order to make the GA work better
// or worse.

  GABin2DecPhenotype map;
  for(i=0; i<n; i++)
    map.add(8, min[i], max[i]);

// Create the template genome using the phenotype map we just made.  The
// GA will use this genome to clone the population that it uses to do the
// evolution.  We pass the objective function to create the genome.  We 
// also use the user data function in the genome to keep track of our
// target values.

  GABin2DecGenome genome(map, Objective, (void *)target);

// Now create the GA using the genome, set the parameters, and run it.

  GASimpleGA ga(genome);
  ga.populationSize(popsize);
  ga.nGenerations(ngen);
  ga.pMutation(pmut);
  ga.pCrossover(pcross);
  ga.scoreFilename("bog.dat");
  ga.flushFrequency(50);	// dump scores to disk every 50th generation
  ga.evolve(seed);

// Dump the results of the GA to the screen.  We print out first what a random
// genome looks like (so we get a bit of a feel for how hard it is for the
// GA to find the right values) then we print out the best genome that the
// GA was able to find.

  genome.initialize();
  cout << "random values in the genome:\n";;
  for(i=0; i<map.nPhenotypes(); i++){
    cout.width(10); cout << genome.phenotype(i) << " ";
  }
  cout << "\n";

  genome = ga.statistics().bestIndividual();
  cout << "the ga generated:\n";
  for(i=0; i<map.nPhenotypes(); i++){
    cout.width(10); cout << genome.phenotype(i) << " ";
  }
  cout << "\n\n"; cout.flush();

// We could print out the genome directly, like this:
// cout << genome << "\n";

  cout << "best of generation data are in 'bog.dat'\n";

// Clean up by freeing the memory we allocated.

  delete [] target;
  return 0;
}
 

// For this objective function we try to match the values in the array of float
// that is passed to us as userData.  If the values in the genome map to 
// values that are close, we return a better score.  We are limited to positive
// values for the objective value (because we're using linear scaling - the
// default scaling method for SimpleGA), so we take the reciprocal of the 
// absolute value of the difference between the value from the phenotype and 
// the value in the sequence.
float
Objective(GAGenome& g)
{
  GABin2DecGenome & genome = (GABin2DecGenome &)g;
  float *sequence = (float *)g.userData();

  float value=genome.nPhenotypes();
  for(int i=0; i<genome.nPhenotypes(); i++)
    value += 1.0 / (1.0 + fabs(genome.phenotype(i) - sequence[i]));
  return value;
}