public float computeFitness(Individual individual) {
float fitness = 0;
int three = 99; // Bogus value. Just to initialize.
char[] levelString = individual.copyIndividual();
int levelSize = Problem.n;
int nLevels = (int) (Math.log(levelSize) / Math.log(3));
float levelFit;
float
flow =
(float) 1
+ (float) 0.1
/ (float) nLevels, // Parameters for trap at all levels except the top one.
fhigh = 1;
float topFlow = (float) 0.9, // Parameters for topTrap
topFhigh = 1;
while (levelSize > 3) { // All levels except the top one.
levelFit = 0; // Fitness contribution of each level.
for (int i = 0; i < levelSize; ) { // Empty increment
three = Integer.parseInt(String.valueOf(levelString[i++]));
three += Integer.parseInt(String.valueOf(levelString[i++]));
three += Integer.parseInt(String.valueOf(levelString[i++]));
if (three == 3) {
levelFit += fhigh; // fhigh = 1.
levelString[i / 3 - 1] =
'1'; // '111' -> 1. NOTE: rewriting over the leftmost part of levelString.
} else if (three == 0) {
levelFit += flow; // flow = 1 + 0.1/l.
levelString[i / 3 - 1] =
'0'; // '000' -> 0. NOTE: rewriting over the leftmost part of levelString.
} else if (three < 3) {
levelFit += flow - ((float) three) * flow / ((float) 2); // flow - u*flow/(k-1).
levelString[i / 3 - 1] =
'8'; // anything else -> 8 (NULL symbol). NOTE: rewriting over the leftmost part of
// levelString.
} else if (three > 3) {
// levelFit += 0 // NULL symbol present.
levelString[i / 3 - 1] =
'8'; // anything else -> 8 (NULL symbol). NOTE: rewriting over the leftmost part of
// levelString.
}
}
levelSize /= 3; // Next levelSize. Each 3-string is collapsed in to a single symbol.
fitness +=
levelFit * Problem.n
/ levelSize; // Each level contribution is multiplied by the factor: 3^level =
// stringSize/(next levelSize).
}
levelFit =
0; // We are at the top level. No need for mapping. Use topTrap as the contribution
// function.
for (int i = 0; i < 3; ) {
three = Integer.parseInt(String.valueOf(levelString[i++]));
three += Integer.parseInt(String.valueOf(levelString[i++]));
three += Integer.parseInt(String.valueOf(levelString[i++]));
}
if (three == 3) levelFit += topFhigh; // topFhigh = 1.
else if (three == 0) levelFit += topFlow; // topFlow = .9.
else if (three < 3)
levelFit += topFlow - ((float) three) * topFlow / ((float) 2); // flow - u*flow/(k-1).
// else NULL symbol present, do nothing.
fitness += levelFit * Problem.n; // At the top level the contribution factor is
return fitness; // 3^nLevels = stringSize.
} // END: computeFitness(...)
