From 78198aff4ce22b0f34e3159c082686b03ac1f939 Mon Sep 17 00:00:00 2001
From: Giorgos Stamatelatos <gstamatelat@gmail.com>
Date: Sat, 27 Jan 2018 17:18:11 +0200
Subject: [PATCH] EfraimidisSampling can have weights 0.0 and 1.0 (#12)

---
 .../java/gr/james/sampling/EfraimidisSampling.java    |  2 +-
 .../gr/james/sampling/WeightedRandomSamplingTest.java | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/main/java/gr/james/sampling/EfraimidisSampling.java b/src/main/java/gr/james/sampling/EfraimidisSampling.java
index b7bf448..2515ab0 100644
--- 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
index 67d0620..98b98d1 100644
--- 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();
+    }
+
 }