/**
* Check if the given action and state is a better policy
*
* @param current - The current state
* @param newActionValue - The value of the new action
* @return true if we have a better policy. False otherwise
*/
private boolean isBetterPolicy(State current, Double newActionValue) {
if (!this.policy.keySet().contains(current)) { // No policy set for this yet
return true;
}
if (current.getCost() <= newActionValue) { // New action has better cost
return true;
}
return false;
}
/**
* Value generation
*
* @param state - The current state
* @param action - The current action
* @param Set<State> lookup - The set of states we are looking up
* @return The total value for that state
*/
private Double valueGeneration(State state, Action action, Set<State> lookup) {
Double maxValue = null; // The maximum value
double currentVal = 0.0; // The current value
List<Double> currentProb = new ArrayList<Double>();
for (State possible : this.possibleStates) {
currentProb = transition(state, action, possible);
for (int i = 0; i < currentProb.size(); ++i) {
currentVal +=
currentProb.get(i)
* (reward(possible) + this.spec.getDiscountFactor() * possible.getCost());
}
if (maxValue == null) { // First time generating value
maxValue = currentVal;
} else { // Need to sum up these values
maxValue += currentVal;
}
}
return maxValue;
}
/**
* Checks if the difference between the values of the previous policy and the new policy are <=
* val.
*
* <p>Also reassigns the old policy
*
* @param double val - The difference
* @param Map<State, Action> newPolicy - The new policy
* @return true if the minimum difference > val. false otherwise
*/
private boolean CheckDifference(double val, Map<State, Action> newPolicy) {
Double currDiff, minDiff = null; // The minimum and current difference
if (this.policy.size() != this.possibleStates.size()) { // Previous policy wasn't assigned yet
return true;
}
for (State current : newPolicy.keySet()) {
for (State old : this.policy.keySet()) {
if (current.equals(old)) {
currDiff = Math.abs(current.getTemporaryCost() - old.getCost());
if (minDiff == null || currDiff <= minDiff) {
minDiff = currDiff;
}
break;
}
}
}
if (minDiff > val) {
return true;
}
return false;
}
