/**
* GT smoothing with least squares interpolation. This follows the procedure in Jurafsky and
* Martin sect. 4.5.3.
*/
public void smoothAndNormalize() {
Counter<Integer> cntCounter = new Counter<Integer>();
for (K tok : lm.keySet()) {
int cnt = (int) lm.getCount(tok);
cntCounter.incrementCount(cnt);
}
final double[] coeffs = runLogSpaceRegression(cntCounter);
UNK_PROB = cntCounter.getCount(1) / lm.totalCount();
for (K tok : lm.keySet()) {
double tokCnt = lm.getCount(tok);
if (tokCnt <= unkCutoff) // Treat as unknown
unkTokens.add(tok);
if (tokCnt <= kCutoff) { // Smooth
double cSmooth = katzEstimate(cntCounter, tokCnt, coeffs);
lm.setCount(tok, cSmooth);
}
}
// Normalize
// Counters.normalize(lm);
// MY COUNTER IS ALWAYS NORMALIZED AND AWESOME
}
public static <E> Counter<E> normalize(Counter<E> counter) {
Counter<E> normalizedCounter = new Counter<E>();
double total = counter.totalCount();
for (E key : counter.keySet()) {
normalizedCounter.setCount(key, counter.getCount(key) / total);
}
return normalizedCounter;
}
/**
* @param <E>
* @param x
* @param y
* @return
*/
public static <E> double jensenShannonDivergence(Counter<E> x, Counter<E> y) {
double sum = 0.0;
double xTotal = x.totalCount();
double yTotal = y.totalCount();
for (E key : x.keySet()) {
// x -> x+y/2
double xVal = x.getCount(key) / xTotal;
double yVal = y.getCount(key) / yTotal;
double avg = 0.5 * (xVal + yVal);
sum += xVal * Math.log(xVal / avg);
}
for (E key : y.keySet()) {
// y -> x+y/2
double xVal = x.getCount(key) / xTotal;
double yVal = y.getCount(key) / yTotal;
double avg = 0.5 * (xVal + yVal);
sum += yVal * Math.log(yVal / avg);
}
return sum / 0.5;
}
public static <E> E sample(Counter<E> counter) {
double total = counter.totalCount();
double rand = random.nextDouble();
double sum = 0.0;
if (total <= 0.0) {
throw new RuntimeException("Non-positive counter total: " + total);
}
for (E key : counter.keySet()) {
double count = counter.getCount(key);
if (count < 0.0) {
throw new RuntimeException("Negative count in counter: " + key + " => " + count);
}
double prob = count / total;
sum += prob;
if (rand < sum) {
return key;
}
}
throw new RuntimeException("Shouldn't Reach Here");
}
public double totalMass() {
return lm.totalCount();
}
