/**
* Make sure that empirical distribution of random Poisson(4)'s has P(X <= 5) close to actual
* cumulative Poisson probability and that nextPoisson fails when mean is non-positive.
*/
@Test
public void testNextPoisson() {
try {
randomData.nextPoisson(0);
Assert.fail("zero mean -- expecting MathIllegalArgumentException");
} catch (MathIllegalArgumentException ex) {
// ignored
}
try {
randomData.nextPoisson(-1);
Assert.fail("negative mean supplied -- MathIllegalArgumentException expected");
} catch (MathIllegalArgumentException ex) {
// ignored
}
try {
randomData.nextPoisson(0);
Assert.fail("0 mean supplied -- MathIllegalArgumentException expected");
} catch (MathIllegalArgumentException ex) {
// ignored
}
final double mean = 4.0d;
final int len = 5;
PoissonDistribution poissonDistribution = new PoissonDistribution(mean);
Frequency f = new Frequency();
randomData.reSeed(1000);
for (int i = 0; i < largeSampleSize; i++) {
f.addValue(randomData.nextPoisson(mean));
}
final long[] observed = new long[len];
for (int i = 0; i < len; i++) {
observed[i] = f.getCount(i + 1);
}
final double[] expected = new double[len];
for (int i = 0; i < len; i++) {
expected[i] = poissonDistribution.probability(i + 1) * largeSampleSize;
}
TestUtils.assertChiSquareAccept(expected, observed, 0.0001);
}
@Test
/** MATH-720 */
public void testReseed() {
PoissonDistribution x = new PoissonDistribution(3.0);
x.reseedRandomGenerator(0);
final double u = x.sample();
PoissonDistribution y = new PoissonDistribution(3.0);
y.reseedRandomGenerator(0);
Assert.assertEquals(u, y.sample(), 0);
}
/**
* Verifies that nextPoisson(mean) generates an empirical distribution of values consistent with
* PoissonDistributionImpl by generating 1000 values, computing a grouped frequency distribution
* of the observed values and comparing this distribution to the corresponding expected
* distribution computed using PoissonDistributionImpl. Uses ChiSquare test of goodness of fit to
* evaluate the null hypothesis that the distributions are the same. If the null hypothesis can be
* rejected with confidence 1 - alpha, the check fails.
*/
public void checkNextPoissonConsistency(double mean) {
// Generate sample values
final int sampleSize = 1000; // Number of deviates to generate
final int minExpectedCount = 7; // Minimum size of expected bin count
long maxObservedValue = 0;
final double alpha = 0.001; // Probability of false failure
Frequency frequency = new Frequency();
for (int i = 0; i < sampleSize; i++) {
long value = randomData.nextPoisson(mean);
if (value > maxObservedValue) {
maxObservedValue = value;
}
frequency.addValue(value);
}
/*
* Set up bins for chi-square test.
* Ensure expected counts are all at least minExpectedCount.
* Start with upper and lower tail bins.
* Lower bin = [0, lower); Upper bin = [upper, +inf).
*/
PoissonDistribution poissonDistribution = new PoissonDistribution(mean);
int lower = 1;
while (poissonDistribution.cumulativeProbability(lower - 1) * sampleSize < minExpectedCount) {
lower++;
}
int upper = (int) (5 * mean); // Even for mean = 1, not much mass beyond 5
while ((1 - poissonDistribution.cumulativeProbability(upper - 1)) * sampleSize
< minExpectedCount) {
upper--;
}
// Set bin width for interior bins. For poisson, only need to look at end bins.
int binWidth = 0;
boolean widthSufficient = false;
double lowerBinMass = 0;
double upperBinMass = 0;
while (!widthSufficient) {
binWidth++;
lowerBinMass = poissonDistribution.cumulativeProbability(lower - 1, lower + binWidth - 1);
upperBinMass = poissonDistribution.cumulativeProbability(upper - binWidth - 1, upper - 1);
widthSufficient = FastMath.min(lowerBinMass, upperBinMass) * sampleSize >= minExpectedCount;
}
/*
* Determine interior bin bounds. Bins are
* [1, lower = binBounds[0]), [lower, binBounds[1]), [binBounds[1], binBounds[2]), ... ,
* [binBounds[binCount - 2], upper = binBounds[binCount - 1]), [upper, +inf)
*
*/
List<Integer> binBounds = new ArrayList<Integer>();
binBounds.add(lower);
int bound = lower + binWidth;
while (bound < upper - binWidth) {
binBounds.add(bound);
bound += binWidth;
}
binBounds.add(
upper); // The size of bin [binBounds[binCount - 2], upper) satisfies binWidth <= size <
// 2*binWidth.
// Compute observed and expected bin counts
final int binCount = binBounds.size() + 1;
long[] observed = new long[binCount];
double[] expected = new double[binCount];
// Bottom bin
observed[0] = 0;
for (int i = 0; i < lower; i++) {
observed[0] += frequency.getCount(i);
}
expected[0] = poissonDistribution.cumulativeProbability(lower - 1) * sampleSize;
// Top bin
observed[binCount - 1] = 0;
for (int i = upper; i <= maxObservedValue; i++) {
observed[binCount - 1] += frequency.getCount(i);
}
expected[binCount - 1] =
(1 - poissonDistribution.cumulativeProbability(upper - 1)) * sampleSize;
// Interior bins
for (int i = 1; i < binCount - 1; i++) {
observed[i] = 0;
for (int j = binBounds.get(i - 1); j < binBounds.get(i); j++) {
observed[i] += frequency.getCount(j);
} // Expected count is (mass in [binBounds[i-1], binBounds[i])) * sampleSize
expected[i] =
(poissonDistribution.cumulativeProbability(binBounds.get(i) - 1)
- poissonDistribution.cumulativeProbability(binBounds.get(i - 1) - 1))
* sampleSize;
}
// Use chisquare test to verify that generated values are poisson(mean)-distributed
ChiSquareTest chiSquareTest = new ChiSquareTest();
// Fail if we can reject null hypothesis that distributions are the same
if (chiSquareTest.chiSquareTest(expected, observed, alpha)) {
StringBuilder msgBuffer = new StringBuilder();
DecimalFormat df = new DecimalFormat("#.##");
msgBuffer.append("Chisquare test failed for mean = ");
msgBuffer.append(mean);
msgBuffer.append(" p-value = ");
msgBuffer.append(chiSquareTest.chiSquareTest(expected, observed));
msgBuffer.append(" chisquare statistic = ");
msgBuffer.append(chiSquareTest.chiSquare(expected, observed));
msgBuffer.append(". \n");
msgBuffer.append("bin\t\texpected\tobserved\n");
for (int i = 0; i < expected.length; i++) {
msgBuffer.append("[");
msgBuffer.append(i == 0 ? 1 : binBounds.get(i - 1));
msgBuffer.append(",");
msgBuffer.append(i == binBounds.size() ? "inf" : binBounds.get(i));
msgBuffer.append(")");
msgBuffer.append("\t\t");
msgBuffer.append(df.format(expected[i]));
msgBuffer.append("\t\t");
msgBuffer.append(observed[i]);
msgBuffer.append("\n");
}
msgBuffer.append("This test can fail randomly due to sampling error with probability ");
msgBuffer.append(alpha);
msgBuffer.append(".");
Assert.fail(msgBuffer.toString());
}
}
@Test
public void testLSHEffect() {
RandomGenerator random = RandomManager.getRandom();
PoissonDistribution itemPerUserDist =
new PoissonDistribution(
random,
20,
PoissonDistribution.DEFAULT_EPSILON,
PoissonDistribution.DEFAULT_MAX_ITERATIONS);
int features = 20;
ALSServingModel mainModel = new ALSServingModel(features, true, 1.0, null);
ALSServingModel lshModel = new ALSServingModel(features, true, 0.5, null);
int userItemCount = 20000;
for (int user = 0; user < userItemCount; user++) {
String userID = "U" + user;
float[] vec = VectorMath.randomVectorF(features, random);
mainModel.setUserVector(userID, vec);
lshModel.setUserVector(userID, vec);
int itemsPerUser = itemPerUserDist.sample();
Collection<String> knownIDs = new ArrayList<>(itemsPerUser);
for (int i = 0; i < itemsPerUser; i++) {
knownIDs.add("I" + random.nextInt(userItemCount));
}
mainModel.addKnownItems(userID, knownIDs);
lshModel.addKnownItems(userID, knownIDs);
}
for (int item = 0; item < userItemCount; item++) {
String itemID = "I" + item;
float[] vec = VectorMath.randomVectorF(features, random);
mainModel.setItemVector(itemID, vec);
lshModel.setItemVector(itemID, vec);
}
int numRecs = 10;
Mean meanMatchLength = new Mean();
for (int user = 0; user < userItemCount; user++) {
String userID = "U" + user;
List<Pair<String, Double>> mainRecs =
mainModel.topN(new DotsFunction(mainModel.getUserVector(userID)), null, numRecs, null);
List<Pair<String, Double>> lshRecs =
lshModel.topN(new DotsFunction(lshModel.getUserVector(userID)), null, numRecs, null);
int i = 0;
while (i < lshRecs.size() && i < mainRecs.size() && lshRecs.get(i).equals(mainRecs.get(i))) {
i++;
}
meanMatchLength.increment(i);
}
log.info("Mean matching prefix: {}", meanMatchLength.getResult());
assertTrue(meanMatchLength.getResult() >= 4.0);
meanMatchLength.clear();
for (int item = 0; item < userItemCount; item++) {
String itemID = "I" + item;
List<Pair<String, Double>> mainRecs =
mainModel.topN(
new CosineAverageFunction(mainModel.getItemVector(itemID)), null, numRecs, null);
List<Pair<String, Double>> lshRecs =
lshModel.topN(
new CosineAverageFunction(lshModel.getItemVector(itemID)), null, numRecs, null);
int i = 0;
while (i < lshRecs.size() && i < mainRecs.size() && lshRecs.get(i).equals(mainRecs.get(i))) {
i++;
}
meanMatchLength.increment(i);
}
log.info("Mean matching prefix: {}", meanMatchLength.getResult());
assertTrue(meanMatchLength.getResult() >= 5.0);
}
