Github user cestella commented on a diff in the pull request:
https://github.com/apache/metron/pull/867#discussion_r156790945
--- Diff:
metron-analytics/metron-statistics/src/main/java/org/apache/metron/statistics/sampling/UniformSampler.java
---
@@ -0,0 +1,91 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.metron.statistics.sampling;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+public class UniformSampler implements Sampler {
+ private List<Object> reservoir;
+ private int seen = 0;
+ private int size;
+ private Random rng = new Random(0);
+
+ public UniformSampler() {
+ this(DEFAULT_SIZE);
+ }
+
+ public UniformSampler(int size) {
+ this.size = size;
+ reservoir = new ArrayList<>(size);
+ }
+
+ @Override
+ public Iterable<Object> get() {
+ return reservoir;
+ }
+
+ /**
+ * Add an object to the reservoir
+ * @param o
+ */
+ public void add(Object o) {
+ if(o == null) {
+ return;
+ }
+ if (reservoir.size() < size) {
+ reservoir.add(o);
+ } else {
+ int rIndex = rng.nextInt(seen + 1);
--- End diff --
Just so I'm clear, up to the reservoir size, we add to the reservoir. When
we're past the reservoir, we do a random replacement as per
https://en.wikipedia.org/wiki/Reservoir_sampling
---
