/*
* 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.library.metric.undirected;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.flink.api.common.accumulators.LongCounter;
import org.apache.flink.api.common.accumulators.LongMaximum;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.graph.AbstractGraphAnalytic;
import org.apache.flink.graph.AnalyticHelper;
import org.apache.flink.graph.Graph;
import org.apache.flink.graph.Vertex;
import org.apache.flink.graph.asm.degree.annotate.undirected.VertexDegree;
import org.apache.flink.graph.asm.result.PrintableResult;
import org.apache.flink.graph.library.metric.undirected.VertexMetrics.Result;
import org.apache.flink.types.LongValue;
import java.io.IOException;
import java.text.NumberFormat;
import static org.apache.flink.api.common.ExecutionConfig.PARALLELISM_DEFAULT;
/**
* Compute the following vertex metrics in an undirected graph:
* - number of vertices
* - number of edges
* - average degree
* - number of triplets
* - maximum degree
* - maximum number of triplets
*
* @param <K> graph ID type
* @param <VV> vertex value type
* @param <EV> edge value type
*/
public class VertexMetrics<K extends Comparable<K>, VV, EV>
extends AbstractGraphAnalytic<K, VV, EV, Result> {
private static final String VERTEX_COUNT = "vertexCount";
private static final String EDGE_COUNT = "edgeCount";
private static final String TRIPLET_COUNT = "tripletCount";
private static final String MAXIMUM_DEGREE = "maximumDegree";
private static final String MAXIMUM_TRIPLETS = "maximumTriplets";
private VertexMetricsHelper<K> vertexMetricsHelper;
// Optional configuration
private boolean includeZeroDegreeVertices = false;
private boolean reduceOnTargetId = false;
private int parallelism = PARALLELISM_DEFAULT;
/**
* By default only the edge set is processed for the computation of degree.
* When this flag is set an additional join is performed against the vertex
* set in order to output vertices with a degree of zero.
*
* @param includeZeroDegreeVertices whether to output vertices with a
* degree of zero
* @return this
*/
public VertexMetrics<K, VV, EV> setIncludeZeroDegreeVertices(boolean includeZeroDegreeVertices) {
this.includeZeroDegreeVertices = includeZeroDegreeVertices;
return this;
}
/**
* The degree can be counted from either the edge source or target IDs.
* By default the source IDs are counted. Reducing on target IDs may
* optimize the algorithm if the input edge list is sorted by target ID.
*
* @param reduceOnTargetId set to {@code true} if the input edge list
* is sorted by target ID
* @return this
*/
public VertexMetrics<K, VV, EV> setReduceOnTargetId(boolean reduceOnTargetId) {
this.reduceOnTargetId = reduceOnTargetId;
return this;
}
/**
* Override the operator parallelism.
*
* @param parallelism operator parallelism
* @return this
*/
public VertexMetrics<K, VV, EV> setParallelism(int parallelism) {
this.parallelism = parallelism;
return this;
}
@Override
public VertexMetrics<K, VV, EV> run(Graph<K, VV, EV> input)
throws Exception {
super.run(input);
DataSet<Vertex<K, LongValue>> vertexDegree = input
.run(new VertexDegree<K, VV, EV>()
.setIncludeZeroDegreeVertices(includeZeroDegreeVertices)
.setReduceOnTargetId(reduceOnTargetId)
.setParallelism(parallelism));
vertexMetricsHelper = new VertexMetricsHelper<>();
vertexDegree
.output(vertexMetricsHelper)
.name("Vertex metrics");
return this;
}
@Override
public Result getResult() {
long vertexCount = vertexMetricsHelper.getAccumulator(env, VERTEX_COUNT);
long edgeCount = vertexMetricsHelper.getAccumulator(env, EDGE_COUNT);
long tripletCount = vertexMetricsHelper.getAccumulator(env, TRIPLET_COUNT);
long maximumDegree = vertexMetricsHelper.getAccumulator(env, MAXIMUM_DEGREE);
long maximumTriplets = vertexMetricsHelper.getAccumulator(env, MAXIMUM_TRIPLETS);
// each edge is counted twice, once from each vertex, so must be halved
return new Result(vertexCount, edgeCount / 2, tripletCount, maximumDegree, maximumTriplets);
}
/**
* Helper class to collect vertex metrics.
*
* @param <T> ID type
*/
private static class VertexMetricsHelper<T>
extends AnalyticHelper<Vertex<T, LongValue>> {
private long vertexCount;
private long edgeCount;
private long tripletCount;
private long maximumDegree;
private long maximumTriplets;
@Override
public void writeRecord(Vertex<T, LongValue> record) throws IOException {
long degree = record.f1.getValue();
long triplets = degree * (degree - 1) / 2;
vertexCount++;
edgeCount += degree;
tripletCount += triplets;
maximumDegree = Math.max(maximumDegree, degree);
maximumTriplets = Math.max(maximumTriplets, triplets);
}
@Override
public void close() throws IOException {
addAccumulator(VERTEX_COUNT, new LongCounter(vertexCount));
addAccumulator(EDGE_COUNT, new LongCounter(edgeCount));
addAccumulator(TRIPLET_COUNT, new LongCounter(tripletCount));
addAccumulator(MAXIMUM_DEGREE, new LongMaximum(maximumDegree));
addAccumulator(MAXIMUM_TRIPLETS, new LongMaximum(maximumTriplets));
}
}
/**
* Wraps vertex metrics.
*/
public static class Result
implements PrintableResult {
private long vertexCount;
private long edgeCount;
private long tripletCount;
private long maximumDegree;
private long maximumTriplets;
public Result(long vertexCount, long edgeCount, long tripletCount, long maximumDegree, long maximumTriplets) {
this.vertexCount = vertexCount;
this.edgeCount = edgeCount;
this.tripletCount = tripletCount;
this.maximumDegree = maximumDegree;
this.maximumTriplets = maximumTriplets;
}
/**
* Get the number of vertices.
*
* @return number of vertices
*/
public long getNumberOfVertices() {
return vertexCount;
}
/**
* Get the number of edges. Each edge is counted once even though Gelly
* stores undirected edges twice, once in each direction.
*
* @return number of edges
*/
public long getNumberOfEdges() {
return edgeCount;
}
/**
* Get the average degree, the average number of edges per vertex.
*
* A result of {@code Float.NaN} is returned for an empty graph for
* which both the number of edges and number of vertices is zero.
*
* @return average degree
*/
public double getAverageDegree() {
// each edge is incident on two vertices
return vertexCount == 0 ? Double.NaN : 2 * edgeCount / (double)vertexCount;
}
/**
* Get the density, the ratio of actual to potential edges between vertices.
*
* A result of {@code Float.NaN} is returned for a graph with fewer than
* two vertices for which the number of edges is zero.
*
* @return density
*/
public double getDensity() {
return vertexCount <= 1 ? Double.NaN : edgeCount / (double)(vertexCount*(vertexCount-1)/2);
}
/**
* Get the number of triplets.
*
* @return number of triplets
*/
public long getNumberOfTriplets() {
return tripletCount;
}
/**
* Get the maximum degree.
*
* @return maximum degree
*/
public long getMaximumDegree() {
return maximumDegree;
}
/**
* Get the maximum triplets.
*
* @return maximum triplets
*/
public long getMaximumTriplets() {
return maximumTriplets;
}
@Override
public String toPrintableString() {
NumberFormat nf = NumberFormat.getInstance();
// format for very small fractional numbers
NumberFormat ff = NumberFormat.getInstance();
ff.setMaximumFractionDigits(8);
return "vertex count: " + nf.format(vertexCount)
+ "; edge count: " + nf.format(edgeCount)
+ "; average degree: " + nf.format(getAverageDegree())
+ "; density: " + ff.format(getDensity())
+ "; triplet count: " + nf.format(tripletCount)
+ "; maximum degree: " + nf.format(maximumDegree)
+ "; maximum triplets: " + nf.format(maximumTriplets);
}
@Override
public int hashCode() {
return new HashCodeBuilder()
.append(vertexCount)
.append(edgeCount)
.append(tripletCount)
.append(maximumDegree)
.append(maximumTriplets)
.hashCode();
}
@Override
public boolean equals(Object obj) {
if (obj == null) { return false; }
if (obj == this) { return true; }
if (obj.getClass() != getClass()) { return false; }
Result rhs = (Result)obj;
return new EqualsBuilder()
.append(vertexCount, rhs.vertexCount)
.append(edgeCount, rhs.edgeCount)
.append(tripletCount, rhs.tripletCount)
.append(maximumDegree, rhs.maximumDegree)
.append(maximumTriplets, rhs.maximumTriplets)
.isEquals();
}
}
}