Implementation specific default weight (gstamatelat#37)

src/main/java/gr/james/sampling/ChaoSampling.java

@@ -6,7 +6,8 @@
  * Implementation of the algorithm by Chao in <b>A general purpose unequal probability sampling plan</b>.
  * <p>
  * According to this algorithm, the probability of an item to be in the final sample is proportional to its relative
- * weight. Weights must be in the range (0,+Inf), otherwise an {@link IllegalWeightException} is thrown.
+ * weight. Weights must be in the range (0,+Inf), otherwise an {@link IllegalWeightException} is thrown. The default
+ * weight in this implementation is {@code 1.0}.
  * <p>
  * This implementation throws {@link StreamOverflowException} if the sum of the weights of the items feeded is
  * {@link Double#POSITIVE_INFINITY}.
@@ -295,7 +296,7 @@ public final long streamSize() {
      */
     @Override
     public boolean feed(T item) {
-        return WeightedRandomSampling.super.feed(item);
+        return this.feed(item, 1.0);
     }
 
     /**

src/main/java/gr/james/sampling/EfraimidisSampling.java

@@ -7,7 +7,7 @@
  * <p>
  * According to this algorithm, the relative weight determines the probability that the item is selected in each of the
  * explicit or implicit item selections of the sampling procedure. Weights must be in the range (0,+Inf), otherwise an
- * {@link IllegalWeightException} is thrown.
+ * {@link IllegalWeightException} is thrown. The default weight in this implementation is {@code 1.0}.
  * <p>
  * This implementation never throws {@link StreamOverflowException}.
  * <p>
@@ -226,7 +226,7 @@ public final long streamSize() {
      */
     @Override
     public boolean feed(T item) {
-        return WeightedRandomSampling.super.feed(item);
+        return this.feed(item, 1.0);
     }
 
     /**

src/main/java/gr/james/sampling/ParetoSampling.java

@@ -7,9 +7,8 @@
  * <p>
  * Weighted are not being assigned a particular meaning or have physical interpretation but the resulting inclusion
  * probabilities are an approximation of the exact model ({@link ChaoSampling}). Weights must be in the range (0,+Inf)
- * but not the value {@code 1.0}, otherwise an {@link IllegalWeightException} is thrown. A side effect of this is that
- * the signatures {@link #feed(Object)}, {@link #feed(Iterable)} and {@link #feed(Iterator)} will always throw
- * {@link IllegalWeightException}.
+ * but not the value {@code 1.0}, otherwise an {@link IllegalWeightException} is thrown. The default weight in this
+ * implementation is {@code 0.5}.
  * <p>
  * This implementation never throws {@link StreamOverflowException}.
  * <p>
@@ -141,7 +140,6 @@ public boolean feed(T item, double weight) {
 
         // Calculate item weight
         final Weighted<T> newItem = new Weighted<>(item, (r * (1 - weight)) / ((1 - r) * weight));
-        assert newItem.weight >= 0.0; // weight can also be 0.0 because of double precision
 
         // Add item to reservoir
         if (pq.size() < sampleSize) {
@@ -232,7 +230,7 @@ public final long streamSize() {
      */
     @Override
     public boolean feed(T item) {
-        return WeightedRandomSampling.super.feed(item);
+        return this.feed(item, 0.5);
     }
 
     /**

src/main/java/gr/james/sampling/SequentialPoissonSampling.java

@@ -7,7 +7,7 @@
  * <p>
  * Weighted are not being assigned a particular meaning or have physical interpretation but the resulting inclusion
  * probabilities are an approximation of the exact model ({@link ChaoSampling}). Weights must be in the range (0,+Inf),
- * otherwise an {@link IllegalWeightException} is thrown.
+ * otherwise an {@link IllegalWeightException} is thrown. The default weight in this implementation is {@code 1.0}.
  * <p>
  * This implementation never throws {@link StreamOverflowException}.
  * <p>
@@ -226,7 +226,7 @@ public final long streamSize() {
      */
     @Override
     public boolean feed(T item) {
-        return WeightedRandomSampling.super.feed(item);
+        return this.feed(item, 1.0);
     }
 
     /**

src/main/java/gr/james/sampling/WeightedRandomSampling.java

@@ -125,9 +125,10 @@ default boolean feed(Map<T, Double> items) {
     /**
      * {@inheritDoc}
      * <p>
-     * This method uses the value {@code 1.0} as weight and is equivalent to
+     * This method uses a value {@code z} set by the specific implementation as weight that guarantees legality. Hence,
+     * this method is equivalent to
      * <pre><code>
-     * feed(item, 1.0);
+     * feed(item, z);
      * </code></pre>
      *
      * @param item {@inheritDoc}
@@ -143,7 +144,7 @@ default boolean feed(T item) {
     /**
      * {@inheritDoc}
      * <p>
-     * This method uses the value {@code 1.0} as weight.
+     * This method uses an implementation specific value as weight.
      *
      * @param items {@inheritDoc}
      * @return {@inheritDoc}
@@ -158,7 +159,7 @@ default boolean feed(Iterator<T> items) {
     /**
      * {@inheritDoc}
      * <p>
-     * This method uses the value {@code 1.0} as weight.
+     * This method uses an implementation specific value as weight.
      *
      * @param items {@inheritDoc}
      * @return {@inheritDoc}

src/test/java/gr/james/sampling/RandomSamplingTest.java

@@ -73,11 +73,7 @@ public void correctness() {
                         final RandomSampling<Integer> alg = impl.get();
 
                         for (int i = 0; i < STREAM; i++) {
-                            if (alg instanceof ParetoSampling) {
-                                ((ParetoSampling<Integer>) alg).feed(i, 0.5);
-                            } else {
-                                alg.feed(i);
-                            }
+                            alg.feed(i);
                         }
 
                         for (int s : alg.sample()) {
@@ -106,7 +102,7 @@ public void correctness() {
                 int c = d.get(i);
                 final double expected = (double) REPS * Math.min(SAMPLE, STREAM) / STREAM;
                 final double actual = (double) c;
-                assertEquals(1, actual / expected, 1e-2);
+                assertEquals(String.format("Correctness failed for streamSize %d", STREAM), 1, actual / expected, 1e-2);
             }
         }
     }