EfraimidisSampling can have weights 0.0 and 1.0 (gstamatelat#12)

motinis · Jan 27, 2018 · 78198af · 78198af
1 parent a6144a7
commit 78198af
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diff --git a/src/main/java/gr/james/sampling/EfraimidisSampling.java b/src/main/java/gr/james/sampling/EfraimidisSampling.java
@@ -102,7 +102,7 @@ public EfraimidisSampling<T> feed(T item, double weight) {
 
         // Calculate item weight
         final Weighted<T> newItem = new Weighted<>(item, Math.pow(r, 1 / weight));
-        assert newItem.weight > 0.0 && newItem.weight < 1.0;
+        assert newItem.weight >= 0.0 && newItem.weight <= 1.0; // weight can also be 0.0 or 1.0 because of double precision
 
         // Add item to reservoir
         if (pq.size() < sampleSize) {

diff --git a/src/test/java/gr/james/sampling/WeightedRandomSamplingTest.java b/src/test/java/gr/james/sampling/WeightedRandomSamplingTest.java
@@ -95,4 +95,15 @@ public void stream() {
         }
     }
 
+    /**
+     * Pass very small and very large weights to check if algorithms fail.
+     */
+    @Test
+    public void cornerWeights() {
+        final WeightedRandomSampling<Integer> alg = impl.get();
+        alg.feed(0, Double.MIN_VALUE);
+        alg.feed(1, Double.MAX_VALUE);
+        alg.sample();
+    }
+
 }