/**
* Perform the mutation operation
*
* @param probability Mutation probability
* @param solution The solution to mutate
* @throws JMException
*/
public void doMutation(double probability, Solution solution) throws JMException {
try {
if ((solution.getType().getClass() == BinarySolutionType.class)
|| (solution.getType().getClass() == BinaryRealSolutionType.class)) {
for (int i = 0; i < solution.getDecisionVariables().length; i++) {
Binary variable = (Binary) solution.getDecisionVariables()[i];
BitSet set = new BitSet(variable.getNumberOfBits());
int count = variable.getNumberOfBits();
double countD = count;
/* number of bits flipped is B(n, p) distributed (n = number of bits, p = mutationProbability),
* this can be approximated with N(np, sqrt(np * (1-p)))
*/
int x =
(int)
Math.round(
Math.sqrt(probability * (1 - probability) * countD)
* pseudoRandom.nextGaussian()
+ countD * probability);
// very low probability in some special cases that x is bigger then the bitcount
x = Math.min(x, count);
Set<Integer> indices = new HashSet<Integer>();
while (indices.size() < x) {
indices.add(pseudoRandom.randInt(0, count - 1));
}
for (Integer j : indices) set.set(j);
variable.bits_.xor(set);
}
} // if
else { // Integer representation
for (int i = 0; i < solution.getDecisionVariables().length; i++)
if (pseudoRandom.randDouble() < probability) {
int value =
(int)
(pseudoRandom.randInt(
(int) solution.getDecisionVariables()[i].getLowerBound(),
(int) solution.getDecisionVariables()[i].getUpperBound()));
solution.getDecisionVariables()[i].setValue(value);
} // if
} // else
} catch (ClassCastException e1) {
Configuration.logger_.severe(
"BitFlipMutation.doMutation: " + "ClassCastException error" + e1.getMessage());
Class cls = java.lang.String.class;
String name = cls.getName();
throw new JMException("Exception in " + name + ".doMutation()");
}
} // doMutation
public static int numViolatedConstraints(Binary b) {
// IVecInt v = bitSetToVecInt(b);
int s = 0;
for (List<Integer> constraint : ProductLineProblem.constraints) {
boolean sat = false;
for (Integer i : constraint) {
int abs = (i < 0) ? -i : i;
boolean sign = i > 0;
if (b.getIth(abs - 1) == sign) {
sat = true;
break;
}
}
if (!sat) {
s++;
}
}
return s;
}