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AverageDegree.java
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AverageDegree.java
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/*
* Copyright © 2014 - 2018 Leipzig University (Database Research Group)
*
* Licensed 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.gradoop.flink.model.impl.operators.sampling.statistics;
import org.apache.flink.api.common.functions.CrossFunction;
import org.apache.flink.api.java.DataSet;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.common.model.impl.pojo.GraphHead;
import org.gradoop.flink.model.api.epgm.LogicalGraph;
import org.gradoop.flink.model.api.operators.UnaryGraphToGraphOperator;
import org.gradoop.flink.model.impl.operators.aggregation.functions.count.VertexCount;
import org.gradoop.flink.model.impl.operators.sampling.statistics.functions.CalculateAverageDegree;
import org.gradoop.flink.model.impl.operators.statistics.VertexDegrees;
import org.gradoop.flink.model.impl.tuples.WithCount;
/**
* Calculates the average degree of a graph and writes it to the graph head.
* Uses: ceiling( sum(vertex degrees) / |vertices| )
*/
public class AverageDegree implements UnaryGraphToGraphOperator {
/**
* {@inheritDoc}
*/
@Override
public LogicalGraph execute(LogicalGraph graph) {
graph = graph.aggregate(new VertexCount());
DataSet<GraphHead> newGraphHead = new VertexDegrees().execute(graph)
.sum(1)
.cross(graph.getGraphHead().first(1))
.with(new CrossFunction<WithCount<GradoopId>, GraphHead, GraphHead>() {
@Override
public GraphHead cross(WithCount<GradoopId> sumDeg, GraphHead graphHead) throws Exception {
graphHead.setProperty(
SamplingEvaluationConstants.PROPERTY_KEY_SUM_DEGREES, sumDeg.getCount());
return graphHead;
}
})
.map(new CalculateAverageDegree(SamplingEvaluationConstants.PROPERTY_KEY_AVERAGE_DEGREE));
return graph.getConfig().getLogicalGraphFactory()
.fromDataSets(newGraphHead, graph.getVertices(), graph.getEdges());
}
@Override
public String getName() {
return AverageDegree.class.getName();
}
}