org.apache.giraph.utils.EdgeIterables.java Source code

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Here is the source code for org.apache.giraph.utils.EdgeIterables.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.giraph.utils;

import com.google.common.collect.Iterables;
import org.apache.giraph.edge.Edge;
import org.apache.giraph.edge.EdgeFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableUtils;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;

/**
 * Utility methods for iterables of edges.
 */
public class EdgeIterables {
    /** Utility classes shouldn't be instantiated. */
    private EdgeIterables() {
    }

    /**
     * Compare two edge iterables element-wise. The edge value type needs
     * to be Comparable.
     *
     * @param e1 First edge iterable
     * @param e2 Second edge iterable
     * @param <I> Vertex id
     * @param <E> Edge value
     * @return Whether the two iterables are equal element-wise
     */
    public static <I extends WritableComparable, E extends WritableComparable> boolean equals(
            Iterable<Edge<I, E>> e1, Iterable<Edge<I, E>> e2) {
        Iterator<Edge<I, E>> i1 = e1.iterator();
        Iterator<Edge<I, E>> i2 = e2.iterator();
        while (i1.hasNext()) {
            if (!i2.hasNext()) {
                return false;
            }
            if (!EdgeComparator.equal(i1.next(), i2.next())) {
                return false;
            }
        }
        return true;
    }

    /**
     * Make a deep copy of an edge iterable and return it as an {@link
     * ArrayList}.
     * Note: this method is slow since it has to deserialize all serialize all
     * the ids and values. It should only be used in unit tests.
     *
     * @param edges Iterable of edges
     * @param <I> Vertex id
     * @param <E> Edge value
     * @return A new list with copies of all the edges
     */
    public static <I extends WritableComparable, E extends WritableComparable> ArrayList<Edge<I, E>> copy(
            Iterable<Edge<I, E>> edges) {
        Configuration conf = new Configuration();
        ArrayList<Edge<I, E>> edgeList = new ArrayList<Edge<I, E>>(Iterables.size(edges));
        for (Edge<I, E> edge : edges) {
            edgeList.add(EdgeFactory.create(WritableUtils.clone(edge.getTargetVertexId(), conf),
                    WritableUtils.clone(edge.getValue(), conf)));
        }
        return edgeList;
    }

    /**
     * Compare two edge iterables up to reordering. The edge value type needs
     * to be Comparable.
     *
     * @param e1 First edge iterable
     * @param e2 Second edge iterable
     * @param <I> Vertex id
     * @param <E> Edge value
     * @return Whether the two iterables are equal up to reordering
     */
    public static <I extends WritableComparable, E extends WritableComparable> boolean sameEdges(
            Iterable<Edge<I, E>> e1, Iterable<Edge<I, E>> e2) {
        ArrayList<Edge<I, E>> edgeList1 = copy(e1);
        ArrayList<Edge<I, E>> edgeList2 = copy(e2);
        Comparator<Edge<I, E>> edgeComparator = new EdgeComparator<I, E>();
        Collections.sort(edgeList1, edgeComparator);
        Collections.sort(edgeList2, edgeComparator);
        return equals(edgeList1, edgeList2);
    }
}