giraph-core/src/main/java/org/apache/giraph/partition/PartitionBalancer.java - giraph - Git at Google

 /*
  * 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.partition;

 import org.apache.giraph.worker.WorkerInfo;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.log4j.Logger;

 import com.google.common.base.Objects;

 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.PriorityQueue;
 import java.util.Set;

 /**
  * Helper class for balancing partitions across a set of workers.
  */
 public class PartitionBalancer {
   /** Partition balancing algorithm */
   public static final String PARTITION_BALANCE_ALGORITHM =
     "hash.partitionBalanceAlgorithm";
   /** No rebalancing during the supersteps */
   public static final String STATIC_BALANCE_ALGORITHM =
     "static";
   /** Rebalance across supersteps by edges */
   public static final String EGDE_BALANCE_ALGORITHM =
     "edges";
   /** Rebalance across supersteps by vertices */
   public static final String VERTICES_BALANCE_ALGORITHM =
     "vertices";
   /** Class logger */
   private static Logger LOG = Logger.getLogger(PartitionBalancer.class);

   /**
    * What value to balance partitions with?  Edges, vertices?
    */
   private enum BalanceValue {
     /** Not chosen */
     UNSET,
     /** Balance with edges */
     EDGES,
     /** Balance with vertices */
     VERTICES
   }

   /**
    * Do not construct this class.
    */
   private PartitionBalancer() { }

   /**
    * Get the value used to balance.
    *
    * @param partitionStat Stats of this partition.
    * @param balanceValue Type of the value to balance.
    * @return Balance value.
    */
   private static long getBalanceValue(PartitionStats partitionStat,
       BalanceValue balanceValue) {
     switch (balanceValue) {
     case EDGES:
       return partitionStat.getEdgeCount();
     case VERTICES:
       return partitionStat.getVertexCount();
     default:
       throw new IllegalArgumentException(
           "getBalanceValue: Illegal balance value " + balanceValue);
     }
   }

   /**
    * Used to sort the partition owners from lowest value to highest value
    */
   private static class PartitionOwnerComparator implements
       Comparator<PartitionOwner> {
     /** Map of owner to stats */
     private final Map<PartitionOwner, PartitionStats> ownerStatMap;
     /** Value type to compare on */
     private final BalanceValue balanceValue;


     /**
      * Only constructor.
      *
      * @param ownerStatMap Map of owners to stats.
      * @param balanceValue Value to balance with.
      */
     public PartitionOwnerComparator(
         Map<PartitionOwner, PartitionStats> ownerStatMap,
         BalanceValue balanceValue) {
       this.ownerStatMap = ownerStatMap;
       this.balanceValue = balanceValue;
     }

     @Override
     public int compare(PartitionOwner owner1, PartitionOwner owner2) {
       return (int)
           (getBalanceValue(ownerStatMap.get(owner1), balanceValue) -
               getBalanceValue(ownerStatMap.get(owner2), balanceValue));
     }
   }

   /**
    * Structure to keep track of how much value a {@link WorkerInfo} has
    * been assigned.
    */
   private static class WorkerInfoAssignments implements
       Comparable<WorkerInfoAssignments> {
     /** Worker info associated */
     private final WorkerInfo workerInfo;
     /** Balance value */
     private final BalanceValue balanceValue;
     /** Map of owner to stats */
     private final Map<PartitionOwner, PartitionStats> ownerStatsMap;
     /** Current value of this object */
     private long value = 0;

     /**
      * Constructor with final values.
      *
      * @param workerInfo Worker info for assignment.
      * @param balanceValue Value used to balance.
      * @param ownerStatsMap Map of owner to stats.
      */
     public WorkerInfoAssignments(
         WorkerInfo workerInfo,
         BalanceValue balanceValue,
         Map<PartitionOwner, PartitionStats> ownerStatsMap) {
       this.workerInfo = workerInfo;
       this.balanceValue = balanceValue;
       this.ownerStatsMap = ownerStatsMap;
     }

     /**
      * Get the total value of all partitions assigned to this worker.
      *
      * @return Total value of all partition assignments.
      */
     public long getValue() {
       return value;
     }

     /**
      * Assign a {@link PartitionOwner} to this {@link WorkerInfo}.
      *
      * @param partitionOwner PartitionOwner to assign.
      */
     public void assignPartitionOwner(
         PartitionOwner partitionOwner) {
       value += getBalanceValue(ownerStatsMap.get(partitionOwner),
           balanceValue);
       if (!partitionOwner.getWorkerInfo().equals(workerInfo)) {
         partitionOwner.setPreviousWorkerInfo(
             partitionOwner.getWorkerInfo());
         partitionOwner.setWorkerInfo(workerInfo);
       } else {
         partitionOwner.setPreviousWorkerInfo(null);
       }
     }

     @Override
     public int compareTo(WorkerInfoAssignments other) {
       return (int)
           (getValue() - ((WorkerInfoAssignments) other).getValue());
     }

     @Override
     public boolean equals(Object obj) {
       return obj instanceof WorkerInfoAssignments &&
           compareTo((WorkerInfoAssignments) obj) == 0;
     }

     @Override
     public int hashCode() {
       return Objects.hashCode(value);
     }
   }

   /**
    * Balance the partitions with an algorithm based on a value.
    *
    * @param conf Configuration to find the algorithm
    * @param partitionOwners All the owners of all partitions
    * @param allPartitionStats All the partition stats
    * @param availableWorkerInfos All the available workers
    * @return Balanced partition owners
    */
   public static Collection<PartitionOwner> balancePartitionsAcrossWorkers(
       Configuration conf,
       Collection<PartitionOwner> partitionOwners,
       Collection<PartitionStats> allPartitionStats,
       Collection<WorkerInfo> availableWorkerInfos) {

     String balanceAlgorithm =
         conf.get(PARTITION_BALANCE_ALGORITHM, STATIC_BALANCE_ALGORITHM);
     if (LOG.isInfoEnabled()) {
       LOG.info("balancePartitionsAcrossWorkers: Using algorithm " +
           balanceAlgorithm);
     }
     BalanceValue balanceValue = BalanceValue.UNSET;
     if (balanceAlgorithm.equals(STATIC_BALANCE_ALGORITHM)) {
       return partitionOwners;
     } else if (balanceAlgorithm.equals(EGDE_BALANCE_ALGORITHM)) {
       balanceValue = BalanceValue.EDGES;
     } else if (balanceAlgorithm.equals(VERTICES_BALANCE_ALGORITHM)) {
       balanceValue = BalanceValue.VERTICES;
     } else {
       throw new IllegalArgumentException(
           "balancePartitionsAcrossWorkers: Illegal balance " +
               "algorithm - " + balanceAlgorithm);
     }

     // Join the partition stats and partition owners by partition id
     Map<Integer, PartitionStats> idStatMap =
         new HashMap<Integer, PartitionStats>();
     for (PartitionStats partitionStats : allPartitionStats) {
       if (idStatMap.put(partitionStats.getPartitionId(), partitionStats) !=
           null) {
         throw new IllegalStateException(
             "balancePartitionsAcrossWorkers: Duplicate partition id " +
                 "for " + partitionStats);
       }
     }
     Map<PartitionOwner, PartitionStats> ownerStatsMap =
         new HashMap<PartitionOwner, PartitionStats>();
     for (PartitionOwner partitionOwner : partitionOwners) {
       PartitionStats partitionStats =
           idStatMap.get(partitionOwner.getPartitionId());
       if (partitionStats == null) {
         throw new IllegalStateException(
             "balancePartitionsAcrossWorkers: Missing partition " +
                 "stats for " + partitionOwner);
       }
       if (ownerStatsMap.put(partitionOwner, partitionStats) != null) {
         throw new IllegalStateException(
             "balancePartitionsAcrossWorkers: Duplicate partition " +
                 "owner " + partitionOwner);
       }
     }
     if (ownerStatsMap.size() != partitionOwners.size()) {
       throw new IllegalStateException(
           "balancePartitionsAcrossWorkers: ownerStats count = " +
               ownerStatsMap.size() + ", partitionOwners count = " +
               partitionOwners.size() + " and should match.");
     }

     List<WorkerInfoAssignments> workerInfoAssignmentsList =
         new ArrayList<WorkerInfoAssignments>(availableWorkerInfos.size());
     for (WorkerInfo workerInfo : availableWorkerInfos) {
       workerInfoAssignmentsList.add(
           new WorkerInfoAssignments(
               workerInfo, balanceValue, ownerStatsMap));
     }

     // A simple heuristic for balancing the partitions across the workers
     // using a value (edges, vertices).  An improvement would be to
     // take into account the already existing partition worker assignments.
     // 1.  Sort the partitions by size
     // 2.  Place the workers in a min heap sorted by their total balance
     //     value.
     // 3.  From largest partition to the smallest, take the partition
     //     worker at the top of the heap, add the partition to it, and
     //     then put it back in the heap
     List<PartitionOwner> partitionOwnerList =
         new ArrayList<PartitionOwner>(partitionOwners);
     Collections.sort(partitionOwnerList,
         Collections.reverseOrder(
             new PartitionOwnerComparator(ownerStatsMap, balanceValue)));
     PriorityQueue<WorkerInfoAssignments> minQueue =
         new PriorityQueue<WorkerInfoAssignments>(workerInfoAssignmentsList);
     for (PartitionOwner partitionOwner : partitionOwnerList) {
       WorkerInfoAssignments chosenWorker = minQueue.remove();
       chosenWorker.assignPartitionOwner(partitionOwner);
       minQueue.add(chosenWorker);
     }

     return partitionOwnerList;
   }

   /**
    * Helper function to update partition owners and determine which
    * partitions need to be sent from a specific worker.
    *
    * @param partitionOwnerList Local {@link PartitionOwner} list for the
    *                           given worker
    * @param myWorkerInfo Worker info
    * @param masterSetPartitionOwners Master set partition owners, received
    *        prior to beginning the superstep
    * @return Information for the partition exchange.
    */
   public static PartitionExchange updatePartitionOwners(
       List<PartitionOwner> partitionOwnerList,
       WorkerInfo myWorkerInfo,
       Collection<? extends PartitionOwner> masterSetPartitionOwners) {
     partitionOwnerList.clear();
     partitionOwnerList.addAll(masterSetPartitionOwners);

     Set<WorkerInfo> dependentWorkerSet = new HashSet<WorkerInfo>();
     Map<WorkerInfo, List<Integer>> workerPartitionOwnerMap =
         new HashMap<WorkerInfo, List<Integer>>();
     for (PartitionOwner partitionOwner : masterSetPartitionOwners) {
       if (partitionOwner.getPreviousWorkerInfo() == null) {
         continue;
       } else if (partitionOwner.getWorkerInfo().equals(
           myWorkerInfo) &&
           partitionOwner.getPreviousWorkerInfo().equals(
               myWorkerInfo)) {
         throw new IllegalStateException(
             "updatePartitionOwners: Impossible to have the same " +
                 "previous and current worker info " + partitionOwner +
                 " as me " + myWorkerInfo);
       } else if (partitionOwner.getWorkerInfo().equals(myWorkerInfo)) {
         dependentWorkerSet.add(partitionOwner.getPreviousWorkerInfo());
       } else if (partitionOwner.getPreviousWorkerInfo().equals(
           myWorkerInfo)) {
         if (workerPartitionOwnerMap.containsKey(
             partitionOwner.getWorkerInfo())) {
           workerPartitionOwnerMap.get(
               partitionOwner.getWorkerInfo()).add(
               partitionOwner.getPartitionId());
         } else {
           List<Integer> tmpPartitionOwnerList = new ArrayList<Integer>();
           tmpPartitionOwnerList.add(partitionOwner.getPartitionId());
           workerPartitionOwnerMap.put(partitionOwner.getWorkerInfo(),
               tmpPartitionOwnerList);
         }
       }
     }

     return new PartitionExchange(dependentWorkerSet,
         workerPartitionOwnerMap);
   }
 }
	/*
	* 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.partition;

	import org.apache.giraph.worker.WorkerInfo;
	import org.apache.hadoop.conf.Configuration;
	import org.apache.log4j.Logger;

	import com.google.common.base.Objects;

	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.Collections;
	import java.util.Comparator;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Map;
	import java.util.PriorityQueue;
	import java.util.Set;

	/**
	* Helper class for balancing partitions across a set of workers.
	*/
	public class PartitionBalancer {
	/** Partition balancing algorithm */
	public static final String PARTITION_BALANCE_ALGORITHM =
	"hash.partitionBalanceAlgorithm";
	/** No rebalancing during the supersteps */
	public static final String STATIC_BALANCE_ALGORITHM =
	"static";
	/** Rebalance across supersteps by edges */
	public static final String EGDE_BALANCE_ALGORITHM =
	"edges";
	/** Rebalance across supersteps by vertices */
	public static final String VERTICES_BALANCE_ALGORITHM =
	"vertices";
	/** Class logger */
	private static Logger LOG = Logger.getLogger(PartitionBalancer.class);

	/**
	* What value to balance partitions with? Edges, vertices?
	*/
	private enum BalanceValue {
	/** Not chosen */
	UNSET,
	/** Balance with edges */
	EDGES,
	/** Balance with vertices */
	VERTICES
	}

	/**
	* Do not construct this class.
	*/
	private PartitionBalancer() { }

	/**
	* Get the value used to balance.
	*
	* @param partitionStat Stats of this partition.
	* @param balanceValue Type of the value to balance.
	* @return Balance value.
	*/
	private static long getBalanceValue(PartitionStats partitionStat,
	BalanceValue balanceValue) {
	switch (balanceValue) {
	case EDGES:
	return partitionStat.getEdgeCount();
	case VERTICES:
	return partitionStat.getVertexCount();
	default:
	throw new IllegalArgumentException(
	"getBalanceValue: Illegal balance value " + balanceValue);
	}
	}

	/**
	* Used to sort the partition owners from lowest value to highest value
	*/
	private static class PartitionOwnerComparator implements
	Comparator<PartitionOwner> {
	/** Map of owner to stats */
	private final Map<PartitionOwner, PartitionStats> ownerStatMap;
	/** Value type to compare on */
	private final BalanceValue balanceValue;


	/**
	* Only constructor.
	*
	* @param ownerStatMap Map of owners to stats.
	* @param balanceValue Value to balance with.
	*/
	public PartitionOwnerComparator(
	Map<PartitionOwner, PartitionStats> ownerStatMap,
	BalanceValue balanceValue) {
	this.ownerStatMap = ownerStatMap;
	this.balanceValue = balanceValue;
	}

	@Override
	public int compare(PartitionOwner owner1, PartitionOwner owner2) {
	return (int)
	(getBalanceValue(ownerStatMap.get(owner1), balanceValue) -
	getBalanceValue(ownerStatMap.get(owner2), balanceValue));
	}
	}

	/**
	* Structure to keep track of how much value a {@link WorkerInfo} has
	* been assigned.
	*/
	private static class WorkerInfoAssignments implements
	Comparable<WorkerInfoAssignments> {
	/** Worker info associated */
	private final WorkerInfo workerInfo;
	/** Balance value */
	private final BalanceValue balanceValue;
	/** Map of owner to stats */
	private final Map<PartitionOwner, PartitionStats> ownerStatsMap;
	/** Current value of this object */
	private long value = 0;

	/**
	* Constructor with final values.
	*
	* @param workerInfo Worker info for assignment.
	* @param balanceValue Value used to balance.
	* @param ownerStatsMap Map of owner to stats.
	*/
	public WorkerInfoAssignments(
	WorkerInfo workerInfo,
	BalanceValue balanceValue,
	Map<PartitionOwner, PartitionStats> ownerStatsMap) {
	this.workerInfo = workerInfo;
	this.balanceValue = balanceValue;
	this.ownerStatsMap = ownerStatsMap;
	}

	/**
	* Get the total value of all partitions assigned to this worker.
	*
	* @return Total value of all partition assignments.
	*/
	public long getValue() {
	return value;
	}

	/**
	* Assign a {@link PartitionOwner} to this {@link WorkerInfo}.
	*
	* @param partitionOwner PartitionOwner to assign.
	*/
	public void assignPartitionOwner(
	PartitionOwner partitionOwner) {
	value += getBalanceValue(ownerStatsMap.get(partitionOwner),
	balanceValue);
	if (!partitionOwner.getWorkerInfo().equals(workerInfo)) {
	partitionOwner.setPreviousWorkerInfo(
	partitionOwner.getWorkerInfo());
	partitionOwner.setWorkerInfo(workerInfo);
	} else {
	partitionOwner.setPreviousWorkerInfo(null);
	}
	}

	@Override
	public int compareTo(WorkerInfoAssignments other) {
	return (int)
	(getValue() - ((WorkerInfoAssignments) other).getValue());
	}

	@Override
	public boolean equals(Object obj) {
	return obj instanceof WorkerInfoAssignments &&
	compareTo((WorkerInfoAssignments) obj) == 0;
	}

	@Override
	public int hashCode() {
	return Objects.hashCode(value);
	}
	}

	/**
	* Balance the partitions with an algorithm based on a value.
	*
	* @param conf Configuration to find the algorithm
	* @param partitionOwners All the owners of all partitions
	* @param allPartitionStats All the partition stats
	* @param availableWorkerInfos All the available workers
	* @return Balanced partition owners
	*/
	public static Collection<PartitionOwner> balancePartitionsAcrossWorkers(
	Configuration conf,
	Collection<PartitionOwner> partitionOwners,
	Collection<PartitionStats> allPartitionStats,
	Collection<WorkerInfo> availableWorkerInfos) {

	String balanceAlgorithm =
	conf.get(PARTITION_BALANCE_ALGORITHM, STATIC_BALANCE_ALGORITHM);
	if (LOG.isInfoEnabled()) {
	LOG.info("balancePartitionsAcrossWorkers: Using algorithm " +
	balanceAlgorithm);
	}
	BalanceValue balanceValue = BalanceValue.UNSET;
	if (balanceAlgorithm.equals(STATIC_BALANCE_ALGORITHM)) {
	return partitionOwners;
	} else if (balanceAlgorithm.equals(EGDE_BALANCE_ALGORITHM)) {
	balanceValue = BalanceValue.EDGES;
	} else if (balanceAlgorithm.equals(VERTICES_BALANCE_ALGORITHM)) {
	balanceValue = BalanceValue.VERTICES;
	} else {
	throw new IllegalArgumentException(
	"balancePartitionsAcrossWorkers: Illegal balance " +
	"algorithm - " + balanceAlgorithm);
	}

	// Join the partition stats and partition owners by partition id
	Map<Integer, PartitionStats> idStatMap =
	new HashMap<Integer, PartitionStats>();
	for (PartitionStats partitionStats : allPartitionStats) {
	if (idStatMap.put(partitionStats.getPartitionId(), partitionStats) !=
	null) {
	throw new IllegalStateException(
	"balancePartitionsAcrossWorkers: Duplicate partition id " +
	"for " + partitionStats);
	}
	}
	Map<PartitionOwner, PartitionStats> ownerStatsMap =
	new HashMap<PartitionOwner, PartitionStats>();
	for (PartitionOwner partitionOwner : partitionOwners) {
	PartitionStats partitionStats =
	idStatMap.get(partitionOwner.getPartitionId());
	if (partitionStats == null) {
	throw new IllegalStateException(
	"balancePartitionsAcrossWorkers: Missing partition " +
	"stats for " + partitionOwner);
	}
	if (ownerStatsMap.put(partitionOwner, partitionStats) != null) {
	throw new IllegalStateException(
	"balancePartitionsAcrossWorkers: Duplicate partition " +
	"owner " + partitionOwner);
	}
	}
	if (ownerStatsMap.size() != partitionOwners.size()) {
	throw new IllegalStateException(
	"balancePartitionsAcrossWorkers: ownerStats count = " +
	ownerStatsMap.size() + ", partitionOwners count = " +
	partitionOwners.size() + " and should match.");
	}

	List<WorkerInfoAssignments> workerInfoAssignmentsList =
	new ArrayList<WorkerInfoAssignments>(availableWorkerInfos.size());
	for (WorkerInfo workerInfo : availableWorkerInfos) {
	workerInfoAssignmentsList.add(
	new WorkerInfoAssignments(
	workerInfo, balanceValue, ownerStatsMap));
	}

	// A simple heuristic for balancing the partitions across the workers
	// using a value (edges, vertices). An improvement would be to
	// take into account the already existing partition worker assignments.
	// 1. Sort the partitions by size
	// 2. Place the workers in a min heap sorted by their total balance
	// value.
	// 3. From largest partition to the smallest, take the partition
	// worker at the top of the heap, add the partition to it, and
	// then put it back in the heap
	List<PartitionOwner> partitionOwnerList =
	new ArrayList<PartitionOwner>(partitionOwners);
	Collections.sort(partitionOwnerList,
	Collections.reverseOrder(
	new PartitionOwnerComparator(ownerStatsMap, balanceValue)));
	PriorityQueue<WorkerInfoAssignments> minQueue =
	new PriorityQueue<WorkerInfoAssignments>(workerInfoAssignmentsList);
	for (PartitionOwner partitionOwner : partitionOwnerList) {
	WorkerInfoAssignments chosenWorker = minQueue.remove();
	chosenWorker.assignPartitionOwner(partitionOwner);
	minQueue.add(chosenWorker);
	}

	return partitionOwnerList;
	}

	/**
	* Helper function to update partition owners and determine which
	* partitions need to be sent from a specific worker.
	*
	* @param partitionOwnerList Local {@link PartitionOwner} list for the
	* given worker
	* @param myWorkerInfo Worker info
	* @param masterSetPartitionOwners Master set partition owners, received
	* prior to beginning the superstep
	* @return Information for the partition exchange.
	*/
	public static PartitionExchange updatePartitionOwners(
	List<PartitionOwner> partitionOwnerList,
	WorkerInfo myWorkerInfo,
	Collection<? extends PartitionOwner> masterSetPartitionOwners) {
	partitionOwnerList.clear();
	partitionOwnerList.addAll(masterSetPartitionOwners);

	Set<WorkerInfo> dependentWorkerSet = new HashSet<WorkerInfo>();
	Map<WorkerInfo, List<Integer>> workerPartitionOwnerMap =
	new HashMap<WorkerInfo, List<Integer>>();
	for (PartitionOwner partitionOwner : masterSetPartitionOwners) {
	if (partitionOwner.getPreviousWorkerInfo() == null) {
	continue;
	} else if (partitionOwner.getWorkerInfo().equals(
	myWorkerInfo) &&
	partitionOwner.getPreviousWorkerInfo().equals(
	myWorkerInfo)) {
	throw new IllegalStateException(
	"updatePartitionOwners: Impossible to have the same " +
	"previous and current worker info " + partitionOwner +
	" as me " + myWorkerInfo);
	} else if (partitionOwner.getWorkerInfo().equals(myWorkerInfo)) {
	dependentWorkerSet.add(partitionOwner.getPreviousWorkerInfo());
	} else if (partitionOwner.getPreviousWorkerInfo().equals(
	myWorkerInfo)) {
	if (workerPartitionOwnerMap.containsKey(
	partitionOwner.getWorkerInfo())) {
	workerPartitionOwnerMap.get(
	partitionOwner.getWorkerInfo()).add(
	partitionOwner.getPartitionId());
	} else {
	List<Integer> tmpPartitionOwnerList = new ArrayList<Integer>();
	tmpPartitionOwnerList.add(partitionOwner.getPartitionId());
	workerPartitionOwnerMap.put(partitionOwner.getWorkerInfo(),
	tmpPartitionOwnerList);
	}
	}
	}

	return new PartitionExchange(dependentWorkerSet,
	workerPartitionOwnerMap);
	}
	}