From 2d8adbf5148543bebc026d984f54cc43b9e9f545 Mon Sep 17 00:00:00 2001
From: Gilles Sadowski <gilleseran@gmail.com>
Date: Sat, 11 Apr 2020 13:42:03 +0200
Subject: [PATCH] Avoid performance degradation of indexed access when using a
 linked list.

Thanks to Artavazd Balaian.

Closes #134.
---
 .../commons/math4/distribution/EnumeratedDistribution.java | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java b/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java
index 5b1cd302d..27f53bde4 100644
--- a/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java
+++ b/src/main/java/org/apache/commons/math4/distribution/EnumeratedDistribution.java
@@ -86,9 +86,8 @@ public class EnumeratedDistribution<T> implements Serializable {
                NotANumberException {
         singletons = new ArrayList<>(pmf.size());
         final double[] probs = new double[pmf.size()];
-
-        for (int i = 0; i < pmf.size(); i++) {
-            final Pair<T, Double> sample = pmf.get(i);
+        int count = 0;
+        for (Pair<T, Double> sample : pmf) {
             singletons.add(sample.getKey());
             final double p = sample.getValue();
             if (p < 0) {
@@ -100,7 +99,7 @@ public class EnumeratedDistribution<T> implements Serializable {
             if (Double.isNaN(p)) {
                 throw new NotANumberException();
             }
-            probs[i] = p;
+            probs[count++] = p;
         }
 
         probabilities = MathArrays.normalizeArray(probs, 1.0);