/*
* 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.io.formats;
import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;
import org.apache.giraph.partition.PartitionUtils;
import org.apache.giraph.worker.WorkerInfo;
import java.util.Collections;
import java.util.List;
import java.util.Random;
/**
* Helper class to generate pseudo-random local edges.
* Like {@link PseudoRandomLocalEdgesHelper}, but for graphs where vertex ids
* are integers.
*/
public class PseudoRandomIntNullLocalEdgesHelper {
/** Minimum ratio of partition-local edges. */
private float minLocalEdgesRatio;
/** Total number of vertices. */
private int numVertices;
/** Total number of partitions. */
private int numPartitions;
/** Average partition size. */
private int partitionSize;
/**
* Constructor.
*
* @param numVertices Total number of vertices.
* @param conf Configuration.
*/
public PseudoRandomIntNullLocalEdgesHelper(int numVertices,
ImmutableClassesGiraphConfiguration conf) {
this.minLocalEdgesRatio = conf.getFloat(
PseudoRandomInputFormatConstants.LOCAL_EDGES_MIN_RATIO,
PseudoRandomInputFormatConstants.LOCAL_EDGES_MIN_RATIO_DEFAULT);
this.numVertices = numVertices;
int numWorkers = conf.getMaxWorkers();
List<WorkerInfo> workerInfos = Collections.nCopies(numWorkers,
new WorkerInfo());
numPartitions = PartitionUtils.computePartitionCount(workerInfos,
numWorkers, conf);
partitionSize = numVertices / numPartitions;
}
/**
* Generate a destination vertex id for the given source vertex,
* using the desired configuration for edge locality and the provided
* pseudo-random generator.
*
* @param sourceVertexId Source vertex id.
* @param rand Pseudo-random generator.
* @return Destination vertex id.
*/
public int generateDestVertex(int sourceVertexId, Random rand) {
if (rand.nextFloat() < minLocalEdgesRatio) {
int partitionId = sourceVertexId % numPartitions;
return partitionId + numPartitions * rand.nextInt(partitionSize);
} else {
return rand.nextInt(numVertices);
}
}
}