package com.mapr.synth;
import com.fasterxml.jackson.databind.JsonNode;
import com.mapr.synth.samplers.ForeignKeySampler;
import org.apache.mahout.math.function.DoubleFunction;
import org.apache.mahout.math.random.*;
import org.junit.Test;
public class ForeignKeySamplerTest {
@Test
public void testSample() {
check(1000, getDistribution(0), new ForeignKeySampler(1000, 0));
check(1000, getDistribution(0.5), new ForeignKeySampler(1000, 0.5));
check(1000, getDistribution(1), new ForeignKeySampler(1000, 0.3));
}
private DoubleFunction getDistribution(final double alpha) {
return new DoubleFunction() {
@Override
public double apply(double rank) {
return Math.pow(rank + 1, -alpha);
}
};
}
private void check(int n, DoubleFunction distribution, Sampler<JsonNode> s) {
int[] counts = new int[n];
for (int i = 0; i < 100000; i++) {
counts[s.sample().asInt()]++;
}
double sum = 0;
double[] p = new double[n];
for (int i = 0; i < n; i++) {
p[i] = distribution.apply(i);
sum += p[i];
}
double z1 = 0;
double z2 = 0;
for (int i = 0; i < n; i++) {
z1 += (p[i] - counts[i] / 100000.0) * Math.log(p[i] / sum);
double expected = p[i] * 100000;
double deviation = expected - counts[i];
z2 += deviation * deviation / expected;
}
System.out.printf("%.4f %.4f\n", z1, z2);
}
}