/*
* Artificial Intelligence for Humans
* Volume 2: Nature Inspired Algorithms
* Java Version
* http://www.aifh.org
* http://www.jeffheaton.com
*
* Code repository:
* https://github.com/jeffheaton/aifh
*
* Copyright 2014 by Jeff Heaton
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* For more information on Heaton Research copyrights, licenses
* and trademarks visit:
* http://www.heatonresearch.com/copyright
*/
package com.heatonresearch.aifh.examples.aco;
import com.heatonresearch.aifh.aco.CostGraph;
import com.heatonresearch.aifh.aco.DiscreteACO;
import com.heatonresearch.aifh.examples.ga.tsp.City;
/**
* Created with IntelliJ IDEA.
* User: jheaton
* Date: 5/7/14
* Time: 4:14 AM
* To change this template use File | Settings | File Templates.
*/
public class TSPExampleACO implements CostGraph {
/**
* The number of cities to visit.
*/
public static final int CITIES = 50;
/**
* The size of the population.
*/
public static final int POPULATION_SIZE = 1000;
/**
* The square size of the map.
*/
public static final int MAP_SIZE = 256;
/**
* The maximum number of iterations to allow to have the same score before giving up.
*/
public static final int MAX_SAME_SOLUTION = 50;
/**
* The cities to visit.
*/
private City cities[];
/**
* Place the cities in random locations.
*/
private void initCities() {
cities = new City[CITIES];
for (int i = 0; i < cities.length; i++) {
int xPos = (int) (Math.random() * MAP_SIZE);
int yPos = (int) (Math.random() * MAP_SIZE);
cities[i] = new City(xPos, yPos);
}
}
/**
* Display the cities in the final path.
*/
public void displaySolution(int[] path) {
boolean first = true;
for (final int aPath : path) {
if (!first)
System.out.print(">");
System.out.print("" + aPath);
first = false;
}
System.out.println();
}
/**
* Setup and solve the TSP.
*/
public void solve() {
StringBuilder builder = new StringBuilder();
initCities();
DiscreteACO aco = new DiscreteACO(this, 50);
int sameSolutionCount = 0;
int iteration = 1;
double lastSolution = Double.MAX_VALUE;
while (sameSolutionCount < MAX_SAME_SOLUTION) {
aco.iteration();
double thisSolution = aco.getBestCost();
builder.setLength(0);
builder.append("Iteration: ");
builder.append(iteration++);
builder.append(", Best Path Length = ");
builder.append(thisSolution);
System.out.println(builder.toString());
if (Math.abs(lastSolution - thisSolution) < 1.0) {
sameSolutionCount++;
} else {
sameSolutionCount = 0;
}
lastSolution = thisSolution;
}
System.out.println("Good solution found:");
int[] best = aco.getBestTour();
displaySolution(best);
}
/**
* Program entry point.
*
* @param args Not used.
*/
public static void main(String args[]) {
TSPExampleACO solve = new TSPExampleACO();
solve.solve();
}
@Override
public double cost(final int sourceNode, final int targetNode) {
City city1 = cities[sourceNode];
City city2 = cities[targetNode];
return city1.proximity(city2);
}
@Override
public int graphSize() {
return CITIES;
}
}