/*
* 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.flink.graph.generator;
import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.functions.FunctionAnnotation.ForwardedFields;
import org.apache.flink.graph.Edge;
import org.apache.flink.graph.Graph;
import org.apache.flink.graph.Vertex;
import org.apache.flink.types.LongValue;
import org.apache.flink.types.NullValue;
import org.apache.flink.util.LongValueSequenceIterator;
import org.apache.flink.util.Preconditions;
/**
* A singleton-edge {@link Graph} contains one or more isolated two-paths.
*/
public class SingletonEdgeGraph
extends AbstractGraphGenerator<LongValue, NullValue, NullValue> {
public static final int MINIMUM_VERTEX_PAIR_COUNT = 1;
// Required to create the DataSource
private final ExecutionEnvironment env;
// Required configuration
private long vertexPairCount;
/**
* An undirected {@link Graph} containing one or more isolated two-paths.
* The in- and out-degree of every vertex is 1. For {@code n} vertices
* there are {@code n/2} components.
*
* @param env the Flink execution environment
* @param vertexPairCount number of pairs of vertices
*/
public SingletonEdgeGraph(ExecutionEnvironment env, long vertexPairCount) {
Preconditions.checkArgument(vertexPairCount >= MINIMUM_VERTEX_PAIR_COUNT,
"Vertex pair count must be at least " + MINIMUM_VERTEX_PAIR_COUNT);
this.env = env;
this.vertexPairCount = vertexPairCount;
}
@Override
public Graph<LongValue, NullValue, NullValue> generate() {
// Vertices
long vertexCount = 2 * this.vertexPairCount;
DataSet<Vertex<LongValue, NullValue>> vertices = GraphGeneratorUtils.vertexSequence(env, parallelism, vertexCount);
// Edges
LongValueSequenceIterator iterator = new LongValueSequenceIterator(0, vertexCount - 1);
DataSet<Edge<LongValue, NullValue>> edges = env
.fromParallelCollection(iterator, LongValue.class)
.setParallelism(parallelism)
.name("Edge iterators")
.map(new LinkVertexToSingletonNeighbor())
.setParallelism(parallelism)
.name("Complete graph edges");
// Graph
return Graph.fromDataSet(vertices, edges, env);
}
@ForwardedFields("*->f0")
private static class LinkVertexToSingletonNeighbor
implements MapFunction<LongValue, Edge<LongValue, NullValue>> {
private LongValue source = new LongValue();
private LongValue target = new LongValue();
private Edge<LongValue, NullValue> edge = new Edge<>(source, target, NullValue.getInstance());
@Override
public Edge<LongValue, NullValue> map(LongValue value) throws Exception {
long val = value.getValue();
source.setValue(val);
if (val % 2 == 0) {
target.setValue(val + 1);
} else {
target.setValue(val - 1);
}
return edge;
}
}
}