Simplify LiLSampling powers

motinis · Jul 2, 2018 · 9a0eba0 · 9a0eba0
1 parent 610a5f7
commit 9a0eba0
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Showing 3 changed files with 6 additions and 4 deletions.
diff --git a/src/main/java/gr/james/sampling/LiLSampling.java b/src/main/java/gr/james/sampling/LiLSampling.java
@@ -51,7 +51,8 @@ public static <E> RandomSamplingCollector<E> collector(int sampleSize, Random ra
 
     @Override
     void init(int sampleSize, Random random) {
-        W = Math.exp(Math.log(RandomSamplingUtils.randomExclusive(random)) / sampleSize);
+        // W = Math.exp(Math.log(RandomSamplingUtils.randomExclusive(random)) / sampleSize);
+        W = Math.pow(RandomSamplingUtils.randomExclusive(random), 1.0 / sampleSize);
     }
 
     @Override
@@ -63,7 +64,8 @@ long skipLength(long streamSize, int sampleSize, Random random) {
         if (skip == Long.MIN_VALUE) {  // Sometimes when W is very small, 1 - W = 1 and Math.log(1) = +0 instead of -0
             skip = Long.MAX_VALUE;     // This results in negative infinity skip
         }
-        W = W * Math.exp(Math.log(random2) / sampleSize);
+        // W = W * Math.exp(Math.log(random2) / sampleSize);
+        W = W * Math.pow(random2, 1.0 / sampleSize);
         return skip;
     }
 }
diff --git a/src/test/java/gr/james/sampling/RandomSamplingTest.java b/src/test/java/gr/james/sampling/RandomSamplingTest.java
@@ -42,7 +42,7 @@ public static Collection<Supplier<RandomSampling<Integer>>> implementations() {
     @Test
     public void correctness() {
         final int[] streamSizes = {1, 20, 100};
-        final int[] repsSizes = {1000000, 1000000, 1000000};
+        final int[] repsSizes = {1000000, 1000000, 2000000};
 
         Assert.assertEquals(streamSizes.length, repsSizes.length);
 

diff --git a/src/test/java/gr/james/sampling/WeightedRandomSamplingTest.java b/src/test/java/gr/james/sampling/WeightedRandomSamplingTest.java
@@ -39,7 +39,7 @@ public static Collection<Supplier<WeightedRandomSampling<Integer>>> implementati
     @Test
     public void correctness() {
         final int[] streamSizes = {1, 20, 100};
-        final int[] repsSizes = {1000000, 1000000, 1000000};
+        final int[] repsSizes = {1000000, 1000000, 2000000};
 
         Assert.assertEquals(streamSizes.length, repsSizes.length);