Merge remote-tracking branch 'upstream/master' into commonKeysInParti…

…tionByBucketBy

common/sketch/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ 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.
+  -->
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>org.apache.spark</groupId>
+    <artifactId>spark-parent_2.10</artifactId>
+    <version>2.0.0-SNAPSHOT</version>
+    <relativePath>../../pom.xml</relativePath>
+  </parent>
+
+  <groupId>org.apache.spark</groupId>
+  <artifactId>spark-sketch_2.10</artifactId>
+  <packaging>jar</packaging>
+  <name>Spark Project Sketch</name>
+  <url>http://spark.apache.org/</url>
+  <properties>
+    <sbt.project.name>sketch</sbt.project.name>
+  </properties>
+
+  <build>
+    <outputDirectory>target/scala-${scala.binary.version}/classes</outputDirectory>
+    <testOutputDirectory>target/scala-${scala.binary.version}/test-classes</testOutputDirectory>
+  </build>
+</project>

common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java

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+/*
+ * 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.spark.util.sketch;
+
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * A Count-Min sketch is a probabilistic data structure used for summarizing streams of data in
+ * sub-linear space.  Currently, supported data types include:
+ * <ul>
+ *   <li>{@link Byte}</li>
+ *   <li>{@link Short}</li>
+ *   <li>{@link Integer}</li>
+ *   <li>{@link Long}</li>
+ *   <li>{@link String}</li>
+ * </ul>
+ * Each {@link CountMinSketch} is initialized with a random seed, and a pair
+ * of parameters:
+ * <ol>
+ *   <li>relative error (or {@code eps}), and
+ *   <li>confidence (or {@code delta})
+ * </ol>
+ * Suppose you want to estimate the number of times an element {@code x} has appeared in a data
+ * stream so far.  With probability {@code delta}, the estimate of this frequency is within the
+ * range {@code true frequency <= estimate <= true frequency + eps * N}, where {@code N} is the
+ * total count of items have appeared the the data stream so far.
+ *
+ * Under the cover, a {@link CountMinSketch} is essentially a two-dimensional {@code long} array
+ * with depth {@code d} and width {@code w}, where
+ * <ul>
+ *   <li>{@code d = ceil(2 / eps)}</li>
+ *   <li>{@code w = ceil(-log(1 - confidence) / log(2))}</li>
+ * </ul>
+ *
+ * See http://www.eecs.harvard.edu/~michaelm/CS222/countmin.pdf for technical details,
+ * including proofs of the estimates and error bounds used in this implementation.
+ *
+ * This implementation is largely based on the {@code CountMinSketch} class from stream-lib.
+ */
+abstract public class CountMinSketch {
+  /**
+   * Returns the relative error (or {@code eps}) of this {@link CountMinSketch}.
+   */
+  public abstract double relativeError();
+
+  /**
+   * Returns the confidence (or {@code delta}) of this {@link CountMinSketch}.
+   */
+  public abstract double confidence();
+
+  /**
+   * Depth of this {@link CountMinSketch}.
+   */
+  public abstract int depth();
+
+  /**
+   * Width of this {@link CountMinSketch}.
+   */
+  public abstract int width();
+
+  /**
+   * Total count of items added to this {@link CountMinSketch} so far.
+   */
+  public abstract long totalCount();
+
+  /**
+   * Adds 1 to {@code item}.
+   */
+  public abstract void add(Object item);
+
+  /**
+   * Adds {@code count} to {@code item}.
+   */
+  public abstract void add(Object item, long count);
+
+  /**
+   * Returns the estimated frequency of {@code item}.
+   */
+  public abstract long estimateCount(Object item);
+
+  /**
+   * Merges another {@link CountMinSketch} with this one in place.
+   *
+   * Note that only Count-Min sketches with the same {@code depth}, {@code width}, and random seed
+   * can be merged.
+   */
+  public abstract CountMinSketch mergeInPlace(CountMinSketch other);
+
+  /**
+   * Writes out this {@link CountMinSketch} to an output stream in binary format.
+   */
+  public abstract void writeTo(OutputStream out);
+
+  /**
+   * Reads in a {@link CountMinSketch} from an input stream.
+   */
+  public static CountMinSketch readFrom(InputStream in) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+
+  /**
+   * Creates a {@link CountMinSketch} with given {@code depth}, {@code width}, and random
+   * {@code seed}.
+   */
+  public static CountMinSketch create(int depth, int width, int seed) {
+    return new CountMinSketchImpl(depth, width, seed);
+  }
+
+  /**
+   * Creates a {@link CountMinSketch} with given relative error ({@code eps}), {@code confidence},
+   * and random {@code seed}.
+   */
+  public static CountMinSketch create(double eps, double confidence, int seed) {
+    return new CountMinSketchImpl(eps, confidence, seed);
+  }
+}