* 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.

*/

* This component translates the optimizer's resulting plan a nephele job graph. The

* translation is a one to one mapping. All decisions are made by the optimizer, this class

* simply creates nephele data structures and descriptions corresponding to the optimizer's

* result.

* <p>

* The basic method of operation is a top down traversal over the plan graph. On the way down, tasks are created

* for the plan nodes, on the way back up, the nodes connect their predecessor.

*/

 

  public static final String MERGE_ITERATION_AUX_TASKS_KEY = "compiler.merge-iteration-aux";

 

  private static final boolean mergeIterationAuxTasks = GlobalConfiguration.getBoolean(MERGE_ITERATION_AUX_TASKS_KEY, false);

 

 

  private static final TaskInChain ALREADY_VISITED_PLACEHOLDER = new TaskInChain(null, null, null);

 

  // ------------------------------------------------------------------------

  private Map<PlanNode, AbstractJobVertex> vertices; // a map from optimizer nodes to nephele vertices

 

  private Map<PlanNode, TaskInChain> chainedTasks; // a map from optimizer nodes to nephele vertices

 

  private Map<IterationPlanNode, IterationDescriptor> iterations;

 

  private List<TaskInChain> chainedTasksInSequence;

 

  private List<AbstractJobVertex> auxVertices; // auxiliary vertices which are added during job graph generation

 

  private final int defaultMaxFan;

 

  private final float defaultSortSpillingThreshold;

 

  private int iterationIdEnumerator = 1;

 

  private IterationPlanNode currentIteration;  // hack: as long as no nesting is possible, remember the enclosing iteration

 

  private SlotSharingGroup sharingGroup;

 

  // ------------------------------------------------------------------------

  /**

   * Creates a new job graph generator that uses the default values for its resource configuration.

   */

  public NepheleJobGraphGenerator() {

    this.defaultMaxFan = ConfigConstants.DEFAULT_SPILLING_MAX_FAN;

    this.defaultSortSpillingThreshold = ConfigConstants.DEFAULT_SORT_SPILLING_THRESHOLD;

  }

 

  public NepheleJobGraphGenerator(Configuration config) {

    this.defaultMaxFan = config.getInteger(ConfigConstants.DEFAULT_SPILLING_MAX_FAN_KEY,

        ConfigConstants.DEFAULT_SPILLING_MAX_FAN);

    this.defaultSortSpillingThreshold = config.getFloat(ConfigConstants.DEFAULT_SORT_SPILLING_THRESHOLD_KEY,

      ConfigConstants.DEFAULT_SORT_SPILLING_THRESHOLD);

  }

  /**

   * Translates a {@link org.apache.flink.compiler.plan.OptimizedPlan} into a

   * {@link org.apache.flink.runtime.jobgraph.JobGraph}.

   * This is an 1-to-1 mapping. No optimization whatsoever is applied.

   *

   * @param program

   *        Optimized PACT plan that is translated into a JobGraph.

   * @return JobGraph generated from PACT plan.

   */

  public JobGraph compileJobGraph(OptimizedPlan program) {

    this.vertices = new HashMap<PlanNode, AbstractJobVertex>();

    this.chainedTasks = new HashMap<PlanNode, TaskInChain>();

    this.chainedTasksInSequence = new ArrayList<TaskInChain>();

    this.auxVertices = new ArrayList<AbstractJobVertex>();

    this.iterations = new HashMap<IterationPlanNode, IterationDescriptor>();

   

    this.sharingGroup = new SlotSharingGroup();

   

    // generate Nephele job graph

    program.accept(this);

   

    // finalize the iterations

    for (IterationDescriptor iteration : this.iterations.values()) {

      if (iteration.getIterationNode() instanceof BulkIterationPlanNode) {

        finalizeBulkIteration(iteration);

      } else if (iteration.getIterationNode() instanceof WorksetIterationPlanNode) {

        finalizeWorksetIteration(iteration);

      } else {

        throw new CompilerException();

      }

    }

   

    // now that the traversal is done, we have the chained tasks write their configs into their

    // parents' configurations

    for (int i = 0; i < this.chainedTasksInSequence.size(); i++) {

      TaskInChain tic = this.chainedTasksInSequence.get(i);

      TaskConfig t = new TaskConfig(tic.getContainingVertex().getConfiguration());

      t.addChainedTask(tic.getChainedTask(), tic.getTaskConfig(), tic.getTaskName());

    }

   

    // create the jobgraph object

    JobGraph graph = new JobGraph(program.getJobName());

    graph.setNumberOfExecutionRetries(program.getOriginalPactPlan().getNumberOfExecutionRetries());

    graph.setAllowQueuedScheduling(false);

   

    // add vertices to the graph

    for (AbstractJobVertex vertex : this.vertices.values()) {

      graph.addVertex(vertex);

    }

   

    for (AbstractJobVertex vertex : this.auxVertices) {

      graph.addVertex(vertex);

      vertex.setSlotSharingGroup(sharingGroup);

    }

   

    // add registered cache file into job configuration

    for (Entry<String, DistributedCacheEntry> e : program.getOriginalPactPlan().getCachedFiles()) {

      DistributedCache.writeFileInfoToConfig(e.getKey(), e.getValue(), graph.getJobConfiguration());

    }

   

    // release all references again

    this.vertices = null;

    this.chainedTasks = null;

    this.chainedTasksInSequence = null;

    this.auxVertices = null;

    this.iterations = null;

    // return job graph

    return graph;

  }

 

  /**

   * This methods implements the pre-visiting during a depth-first traversal. It create the job vertex and

   * sets local strategy.

   *

   * @param node

   *        The node that is currently processed.

   * @return True, if the visitor should descend to the node's children, false if not.

   * @see org.apache.flink.util.Visitor#preVisit(org.apache.flink.util.Visitable)

   */

  @Override

  public boolean preVisit(PlanNode node) {

    // check if we have visited this node before. in non-tree graphs, this happens

    if (this.vertices.containsKey(node) || this.chainedTasks.containsKey(node) || this.iterations.containsKey(node)) {

      // return false to prevent further descend

      return false;

    }

    // the vertex to be created for the current node

    final AbstractJobVertex vertex;

    try {

      if (node instanceof SinkPlanNode) {

        vertex = createDataSinkVertex((SinkPlanNode) node);

      }

      else if (node instanceof SourcePlanNode) {

        vertex = createDataSourceVertex((SourcePlanNode) node);

      }

      else if (node instanceof BulkIterationPlanNode) {

        BulkIterationPlanNode iterationNode = (BulkIterationPlanNode) node;

        // for the bulk iteration, we skip creating anything for now. we create the graph

        // for the step function in the post visit.

       

        // check that the root of the step function has the same DOP as the iteration.

        // because the tail must have the same DOP as the head, we can only merge the last

        // operator with the tail, if they have the same DOP. not merging is currently not

        // implemented

        PlanNode root = iterationNode.getRootOfStepFunction();

        if (root.getDegreeOfParallelism() != node.getDegreeOfParallelism())

        {

          throw new CompilerException("Error: The final operator of the step " +

              "function has a different degree of parallelism than the iteration operator itself.");

        }

       

        IterationDescriptor descr = new IterationDescriptor(iterationNode, this.iterationIdEnumerator++);

        this.iterations.put(iterationNode, descr);

        vertex = null;

      }

      else if (node instanceof WorksetIterationPlanNode) {

        WorksetIterationPlanNode iterationNode = (WorksetIterationPlanNode) node;

        // we have the same constraints as for the bulk iteration

        PlanNode nextWorkSet = iterationNode.getNextWorkSetPlanNode();

        PlanNode solutionSetDelta  = iterationNode.getSolutionSetDeltaPlanNode();

       

        if (nextWorkSet.getDegreeOfParallelism() != node.getDegreeOfParallelism())

        {

          throw new CompilerException("It is currently not supported that the final operator of the step " +

              "function has a different degree of parallelism than the iteration operator itself.");

        }

        if (solutionSetDelta.getDegreeOfParallelism() != node.getDegreeOfParallelism())

        {

          throw new CompilerException("It is currently not supported that the final operator of the step " +

              "function has a different degree of parallelism than the iteration operator itself.");

        }

       

        IterationDescriptor descr = new IterationDescriptor(iterationNode, this.iterationIdEnumerator++);

        this.iterations.put(iterationNode, descr);

        vertex = null;

      }

      else if (node instanceof SingleInputPlanNode) {

        vertex = createSingleInputVertex((SingleInputPlanNode) node);

      }

      else if (node instanceof DualInputPlanNode) {

        vertex = createDualInputVertex((DualInputPlanNode) node);

      }

      else if (node instanceof NAryUnionPlanNode) {

        // skip the union for now

        vertex = null;

      }

      else if (node instanceof BulkPartialSolutionPlanNode) {

        // create a head node (or not, if it is merged into its successor)

        vertex = createBulkIterationHead((BulkPartialSolutionPlanNode) node);

      }

      else if (node instanceof SolutionSetPlanNode) {

        // this represents an access into the solution set index.

        // we do not create a vertex for the solution set here (we create the head at the workset place holder)

       

        // we adjust the joins / cogroups that go into the solution set here

        for (Channel c : node.getOutgoingChannels()) {

          DualInputPlanNode target = (DualInputPlanNode) c.getTarget();

          AbstractJobVertex accessingVertex = this.vertices.get(target);

          TaskConfig conf = new TaskConfig(accessingVertex.getConfiguration());

          int inputNum = c == target.getInput1() ? 0 : c == target.getInput2() ? 1 : -1;

         

          // sanity checks

          if (inputNum == -1) {

            throw new CompilerException();

          }

         

          // adjust the driver

          if (conf.getDriver().equals(MatchDriver.class)) {

            conf.setDriver(inputNum == 0 ? JoinWithSolutionSetFirstDriver.class : JoinWithSolutionSetSecondDriver.class);

          }

          else if (conf.getDriver().equals(CoGroupDriver.class)) {

            conf.setDriver(inputNum == 0 ? CoGroupWithSolutionSetFirstDriver.class : CoGroupWithSolutionSetSecondDriver.class);

          }

          else {

            throw new CompilerException("Found join with solution set using incompatible operator (only Join/CoGroup are valid).");

          }

        }

       

        // make sure we do not visit this node again. for that, we add a 'already seen' entry into one of the sets

        this.chainedTasks.put(node, ALREADY_VISITED_PLACEHOLDER);

       

        vertex = null;

      }

      else if (node instanceof WorksetPlanNode) {

        // create the iteration head here

        vertex = createWorksetIterationHead((WorksetPlanNode) node);

      }

      else {

        throw new CompilerException("Unrecognized node type: " + node.getClass().getName());

      }

    }

    catch (Exception e) {

      throw new CompilerException("Error translating node '" + node + "': " + e.getMessage(), e);

    }

   

    // check if a vertex was created, or if it was chained or skipped

    if (vertex != null) {

      // set degree of parallelism

      int pd = node.getDegreeOfParallelism();

      vertex.setParallelism(pd);

     

      vertex.setSlotSharingGroup(sharingGroup);

     

      // check whether this vertex is part of an iteration step function

      if (this.currentIteration != null) {

        // check that the task has the same DOP as the iteration as such

        PlanNode iterationNode = (PlanNode) this.currentIteration;

        if (iterationNode.getDegreeOfParallelism() < pd) {

          throw new CompilerException("Error: All functions that are part of an iteration must have the same, or a lower, degree-of-parallelism than the iteration operator.");

        }

        // store the id of the iterations the step functions participate in

        IterationDescriptor descr = this.iterations.get(this.currentIteration);

        new TaskConfig(vertex.getConfiguration()).setIterationId(descr.getId());

      }

 

      // store in the map

      this.vertices.put(node, vertex);

    }

    // returning true causes deeper descend

    return true;

  }

  /**

   * This method implements the post-visit during the depth-first traversal. When the post visit happens,

   * all of the descendants have been processed, so this method connects all of the current node's

   * predecessors to the current node.

   *

   * @param node

   *        The node currently processed during the post-visit.

   * @see org.apache.flink.util.Visitor#postVisit(org.apache.flink.util.Visitable) t

   */

  @Override

  public void postVisit(PlanNode node) {

    try {

      // --------- check special cases for which we handle post visit differently ----------

     

      // skip data source node (they have no inputs)

      // also, do nothing for union nodes, we connect them later when gathering the inputs for a task

      // solution sets have no input. the initial solution set input is connected when the iteration node is in its postVisit

      if (node instanceof SourcePlanNode || node instanceof NAryUnionPlanNode || node instanceof SolutionSetPlanNode) {

        return;

      }

     

      // check if we have an iteration. in that case, translate the step function now

      if (node instanceof IterationPlanNode) {

        // for now, prevent nested iterations

        if (this.currentIteration != null) {

          throw new CompilerException("Nested Iterations are not possible at the moment!");

        }

        this.currentIteration = (IterationPlanNode) node;

        this.currentIteration.acceptForStepFunction(this);

        this.currentIteration = null;

       

        // inputs for initial bulk partial solution or initial workset are already connected to the iteration head in the head's post visit.

        // connect the initial solution set now.

        if (node instanceof WorksetIterationPlanNode) {

          // connect the initial solution set

          WorksetIterationPlanNode wsNode = (WorksetIterationPlanNode) node;

          AbstractJobVertex headVertex = this.iterations.get(wsNode).getHeadTask();

          TaskConfig headConfig = new TaskConfig(headVertex.getConfiguration());

          int inputIndex = headConfig.getDriverStrategy().getNumInputs();

          headConfig.setIterationHeadSolutionSetInputIndex(inputIndex);

          translateChannel(wsNode.getInitialSolutionSetInput(), inputIndex, headVertex, headConfig, false);

        }

       

        return;

      }

     

      final AbstractJobVertex targetVertex = this.vertices.get(node);

     

     

      // --------- Main Path: Translation of channels ----------

      //

      // There are two paths of translation: One for chained tasks (or merged tasks in general),

      // which do not have their own task vertex. The other for tasks that have their own vertex,

      // or are the primary task in a vertex (to which the others are chained).

     

      // check whether this node has its own task, or is merged with another one

      if (targetVertex == null) {

        // node's task is merged with another task. it is either chained, of a merged head vertex

        // from an iteration

        final TaskInChain chainedTask;

        if ((chainedTask = this.chainedTasks.get(node)) != null) {

          // Chained Task. Sanity check first...

          final Iterator<Channel> inConns = node.getInputs().iterator();

          if (!inConns.hasNext()) {

            throw new CompilerException("Bug: Found chained task with no input.");

          }

          final Channel inConn = inConns.next();

         

          if (inConns.hasNext()) {

            throw new CompilerException("Bug: Found a chained task with more than one input!");

          }

          if (inConn.getLocalStrategy() != null && inConn.getLocalStrategy() != LocalStrategy.NONE) {

            throw new CompilerException("Bug: Found a chained task with an input local strategy.");

          }

          if (inConn.getShipStrategy() != null && inConn.getShipStrategy() != ShipStrategyType.FORWARD) {

            throw new CompilerException("Bug: Found a chained task with an input ship strategy other than FORWARD.");

          }

 

          AbstractJobVertex container = chainedTask.getContainingVertex();

         

          if (container == null) {

            final PlanNode sourceNode = inConn.getSource();

            container = this.vertices.get(sourceNode);

            if (container == null) {

              // predecessor is itself chained

              container = this.chainedTasks.get(sourceNode).getContainingVertex();

              if (container == null) {

                throw new IllegalStateException("Bug: Chained task predecessor has not been assigned its containing vertex.");

              }

            } else {

              // predecessor is a proper task job vertex and this is the first chained task. add a forward connection entry.

              new TaskConfig(container.getConfiguration()).addOutputShipStrategy(ShipStrategyType.FORWARD);

            }

            chainedTask.setContainingVertex(container);

          }

         

          // add info about the input serializer type

          chainedTask.getTaskConfig().setInputSerializer(inConn.getSerializer(), 0);

         

          // update name of container task

          String containerTaskName = container.getName();

          if(containerTaskName.startsWith("CHAIN ")) {

            container.setName(containerTaskName+" -> "+chainedTask.getTaskName());

          } else {

            container.setName("CHAIN "+containerTaskName+" -> "+chainedTask.getTaskName());

          }

         

          this.chainedTasksInSequence.add(chainedTask);

          return;

        }

        else if (node instanceof BulkPartialSolutionPlanNode ||

            node instanceof WorksetPlanNode)

        {

          // merged iteration head task. the task that the head is merged with will take care of it

          return;

        } else {

          throw new CompilerException("Bug: Unrecognized merged task vertex.");

        }

      }

     

      // -------- Here, we translate non-chained tasks -------------

     

     

      if (this.currentIteration != null) {

        AbstractJobVertex head = this.iterations.get(this.currentIteration).getHeadTask();

        // the head may still be null if we descend into the static parts first

        if (head != null) {

          targetVertex.setStrictlyCoLocatedWith(head);

        }

      }

     

     

      // create the config that will contain all the description of the inputs

      final TaskConfig targetVertexConfig = new TaskConfig(targetVertex.getConfiguration());

           

      // get the inputs. if this node is the head of an iteration, we obtain the inputs from the

      // enclosing iteration node, because the inputs are the initial inputs to the iteration.

      final Iterator<Channel> inConns;

      if (node instanceof BulkPartialSolutionPlanNode) {

        inConns = ((BulkPartialSolutionPlanNode) node).getContainingIterationNode().getInputs().iterator();

        // because the partial solution has its own vertex, is has only one (logical) input.

        // note this in the task configuration

        targetVertexConfig.setIterationHeadPartialSolutionOrWorksetInputIndex(0);

      } else if (node instanceof WorksetPlanNode) {

        WorksetPlanNode wspn = (WorksetPlanNode) node;

        // input that is the initial workset

        inConns = Collections.singleton(wspn.getContainingIterationNode().getInput2()).iterator();

       

        // because we have a stand-alone (non-merged) workset iteration head, the initial workset will

        // be input 0 and the solution set will be input 1

        targetVertexConfig.setIterationHeadPartialSolutionOrWorksetInputIndex(0);

        targetVertexConfig.setIterationHeadSolutionSetInputIndex(1);

      } else {

        inConns = node.getInputs().iterator();

      }

      if (!inConns.hasNext()) {

        throw new CompilerException("Bug: Found a non-source task with no input.");

      }

     

      int inputIndex = 0;

      while (inConns.hasNext()) {

        Channel input = inConns.next();

        inputIndex += translateChannel(input, inputIndex, targetVertex, targetVertexConfig, false);

      }

      // broadcast variables

      int broadcastInputIndex = 0;

      for (NamedChannel broadcastInput: node.getBroadcastInputs()) {

        int broadcastInputIndexDelta = translateChannel(broadcastInput, broadcastInputIndex, targetVertex, targetVertexConfig, true);

        targetVertexConfig.setBroadcastInputName(broadcastInput.getName(), broadcastInputIndex);

        targetVertexConfig.setBroadcastInputSerializer(broadcastInput.getSerializer(), broadcastInputIndex);

        broadcastInputIndex += broadcastInputIndexDelta;

      }

    } catch (Exception e) {

      throw new CompilerException(

        "An error occurred while translating the optimized plan to a nephele JobGraph: " + e.getMessage(), e);

    }

  }

 

  private int translateChannel(Channel input, int inputIndex, AbstractJobVertex targetVertex,

      TaskConfig targetVertexConfig, boolean isBroadcast) throws Exception

  {

    final PlanNode inputPlanNode = input.getSource();

    final Iterator<Channel> allInChannels;

   

    if (inputPlanNode instanceof NAryUnionPlanNode) {

      allInChannels = ((NAryUnionPlanNode) inputPlanNode).getListOfInputs().iterator();

    }

    else if (inputPlanNode instanceof BulkPartialSolutionPlanNode) {

      if (this.vertices.get(inputPlanNode) == null) {

        // merged iteration head

        final BulkPartialSolutionPlanNode pspn = (BulkPartialSolutionPlanNode) inputPlanNode;

        final BulkIterationPlanNode iterationNode = pspn.getContainingIterationNode();

       

        // check if the iteration's input is a union

        if (iterationNode.getInput().getSource() instanceof NAryUnionPlanNode) {

          allInChannels = ((NAryUnionPlanNode) iterationNode.getInput().getSource()).getInputs().iterator();

        } else {

          allInChannels = Collections.singletonList(iterationNode.getInput()).iterator();

        }

       

        // also, set the index of the gate with the partial solution

        targetVertexConfig.setIterationHeadPartialSolutionOrWorksetInputIndex(inputIndex);

      } else {

        // standalone iteration head

        allInChannels = Collections.singletonList(input).iterator();

      }

    } else if (inputPlanNode instanceof WorksetPlanNode) {

      if (this.vertices.get(inputPlanNode) == null) {

        // merged iteration head

        final WorksetPlanNode wspn = (WorksetPlanNode) inputPlanNode;

        final WorksetIterationPlanNode iterationNode = wspn.getContainingIterationNode();

       

        // check if the iteration's input is a union

        if (iterationNode.getInput2().getSource() instanceof NAryUnionPlanNode) {

          allInChannels = ((NAryUnionPlanNode) iterationNode.getInput2().getSource()).getInputs().iterator();

        } else {

          allInChannels = Collections.singletonList(iterationNode.getInput2()).iterator();

        }

       

        // also, set the index of the gate with the partial solution

        targetVertexConfig.setIterationHeadPartialSolutionOrWorksetInputIndex(inputIndex);

      } else {

        // standalone iteration head

        allInChannels = Collections.singletonList(input).iterator();

      }

    } else if (inputPlanNode instanceof SolutionSetPlanNode) {

      // for now, skip connections with the solution set node, as this is a local index access (later to be parameterized here)

      // rather than a vertex connection

      return 0;

    } else {

      allInChannels = Collections.singletonList(input).iterator();

    }

   

    // check that the type serializer is consistent

    TypeSerializerFactory<?> typeSerFact = null;

   

    // accounting for channels on the dynamic path

    int numChannelsTotal = 0;

    int numChannelsDynamicPath = 0;

    int numDynamicSenderTasksTotal = 0;

   

    // expand the channel to all the union channels, in case there is a union operator at its source

    while (allInChannels.hasNext()) {

      final Channel inConn = allInChannels.next();

     

      // sanity check the common serializer

      if (typeSerFact == null) {

        typeSerFact = inConn.getSerializer();

      } else if (!typeSerFact.equals(inConn.getSerializer())) {

        throw new CompilerException("Conflicting types in union operator.");

      }

     

      final PlanNode sourceNode = inConn.getSource();

      AbstractJobVertex sourceVertex = this.vertices.get(sourceNode);

      TaskConfig sourceVertexConfig;

      if (sourceVertex == null) {

        // this predecessor is chained to another task or an iteration

        final TaskInChain chainedTask;

        final IterationDescriptor iteration;

        if ((chainedTask = this.chainedTasks.get(sourceNode)) != null) {

          // push chained task

          if (chainedTask.getContainingVertex() == null) {

            throw new IllegalStateException("Bug: Chained task has not been assigned its containing vertex when connecting.");

          }

          sourceVertex = chainedTask.getContainingVertex();

          sourceVertexConfig = chainedTask.getTaskConfig();

        } else if ((iteration = this.iterations.get(sourceNode)) != null) {

          // predecessor is an iteration

          sourceVertex = iteration.getHeadTask();

          sourceVertexConfig = iteration.getHeadFinalResultConfig();

        } else {

          throw new CompilerException("Bug: Could not resolve source node for a channel.");

        }

      } else {

        // predecessor is its own vertex

        sourceVertexConfig = new TaskConfig(sourceVertex.getConfiguration());

      }

      DistributionPattern pattern = connectJobVertices(

        inConn, inputIndex, sourceVertex, sourceVertexConfig, targetVertex, targetVertexConfig, isBroadcast);

     

      // accounting on channels and senders

      numChannelsTotal++;

      if (inConn.isOnDynamicPath()) {

        numChannelsDynamicPath++;

        numDynamicSenderTasksTotal += getNumberOfSendersPerReceiver(pattern,

          sourceVertex.getParallelism(), targetVertex.getParallelism());

      }

    }

   

    // for the iterations, check that the number of dynamic channels is the same as the number

    // of channels for this logical input. this condition is violated at the moment, if there

    // is a union between nodes on the static and nodes on the dynamic path

    if (numChannelsDynamicPath > 0 && numChannelsTotal != numChannelsDynamicPath) {

      throw new CompilerException("Error: It is currently not supported to union between dynamic and static path in an iteration.");

    }

    if (numDynamicSenderTasksTotal > 0) {

      if (isBroadcast) {

        targetVertexConfig.setBroadcastGateIterativeWithNumberOfEventsUntilInterrupt(inputIndex, numDynamicSenderTasksTotal);

      } else {

        targetVertexConfig.setGateIterativeWithNumberOfEventsUntilInterrupt(inputIndex, numDynamicSenderTasksTotal);

      }

    }

   

    // the local strategy is added only once. in non-union case that is the actual edge,

    // in the union case, it is the edge between union and the target node

    addLocalInfoFromChannelToConfig(input, targetVertexConfig, inputIndex, isBroadcast);

    return 1;

  }

 

  private int getNumberOfSendersPerReceiver(DistributionPattern pattern, int numSenders, int numReceivers) {

    if (pattern == DistributionPattern.BIPARTITE) {

      return numSenders;

    } else if (pattern == DistributionPattern.POINTWISE) {

      if (numSenders != numReceivers) {

        if (numReceivers == 1) {

          return numSenders;

        }

        else if (numSenders == 1) {

          return 1;

        }

        else {

          throw new CompilerException("Error: A changing degree of parallelism is currently " +

              "not supported between tasks within an iteration.");

        }

      } else {

        return 1;

      }

    } else {

      throw new CompilerException("Unknown distribution pattern for channels: " + pattern);

    }

  }

 

  // ------------------------------------------------------------------------

  // Methods for creating individual vertices

  // ------------------------------------------------------------------------

 

  private AbstractJobVertex createSingleInputVertex(SingleInputPlanNode node) throws CompilerException {

    final String taskName = node.getNodeName();

    final DriverStrategy ds = node.getDriverStrategy();

   

    // check, whether chaining is possible

    boolean chaining = false;

    {

      Channel inConn = node.getInput();

      PlanNode pred = inConn.getSource();

      chaining = ds.getPushChainDriverClass() != null &&

          !(pred instanceof NAryUnionPlanNode) &&  // first op after union is stand-alone, because union is merged

          !(pred instanceof BulkPartialSolutionPlanNode) &&  // partial solution merges anyways

          !(pred instanceof WorksetPlanNode) &&  // workset merges anyways

          !(pred instanceof IterationPlanNode) && // cannot chain with iteration heads currently

          inConn.getShipStrategy() == ShipStrategyType.FORWARD &&

          inConn.getLocalStrategy() == LocalStrategy.NONE &&

          pred.getOutgoingChannels().size() == 1 &&

          node.getDegreeOfParallelism() == pred.getDegreeOfParallelism() &&

          node.getBroadcastInputs().isEmpty();

     

      // cannot chain the nodes that produce the next workset or the next solution set, if they are not the

      // in a tail

      if (this.currentIteration != null && this.currentIteration instanceof WorksetIterationPlanNode &&

          node.getOutgoingChannels().size() > 0)

      {

        WorksetIterationPlanNode wspn = (WorksetIterationPlanNode) this.currentIteration;

        if (wspn.getSolutionSetDeltaPlanNode() == pred || wspn.getNextWorkSetPlanNode() == pred) {

          chaining = false;

        }

      }

      // cannot chain the nodes that produce the next workset in a bulk iteration if a termination criterion follows

      if (this.currentIteration != null && this.currentIteration instanceof BulkIterationPlanNode)

      {

        BulkIterationPlanNode wspn = (BulkIterationPlanNode) this.currentIteration;

        if (node == wspn.getRootOfTerminationCriterion() && wspn.getRootOfStepFunction() == pred){

          chaining = false;

        }else if(node.getOutgoingChannels().size() > 0 &&(wspn.getRootOfStepFunction() == pred ||

            wspn.getRootOfTerminationCriterion() == pred)) {

          chaining = false;

        }

      }

    }

   

    final AbstractJobVertex vertex;

    final TaskConfig config;

   

    if (chaining) {

      vertex = null;

      config = new TaskConfig(new Configuration());

      this.chainedTasks.put(node, new TaskInChain(ds.getPushChainDriverClass(), config, taskName));

    } else {

      // create task vertex

      vertex = new AbstractJobVertex(taskName);

      vertex.setInvokableClass((this.currentIteration != null && node.isOnDynamicPath()) ? IterationIntermediatePactTask.class : RegularPactTask.class);

     

      config = new TaskConfig(vertex.getConfiguration());

      config.setDriver(ds.getDriverClass());

    }

   

    // set user code

    config.setStubWrapper(node.getPactContract().getUserCodeWrapper());

    config.setStubParameters(node.getPactContract().getParameters());

   

    // set the driver strategy

    config.setDriverStrategy(ds);

    for(int i=0;i<ds.getNumRequiredComparators();i++) {

      config.setDriverComparator(node.getComparator(i), i);

    }

    // assign memory, file-handles, etc.

    assignDriverResources(node, config);

    return vertex;

  }

  private AbstractJobVertex createDualInputVertex(DualInputPlanNode node) throws CompilerException {

    final String taskName = node.getNodeName();

    final DriverStrategy ds = node.getDriverStrategy();

    final AbstractJobVertex vertex = new AbstractJobVertex(taskName);

    final TaskConfig config = new TaskConfig(vertex.getConfiguration());

    vertex.setInvokableClass( (this.currentIteration != null && node.isOnDynamicPath()) ? IterationIntermediatePactTask.class : RegularPactTask.class);

   

    // set user code

    config.setStubWrapper(node.getPactContract().getUserCodeWrapper());

    config.setStubParameters(node.getPactContract().getParameters());

   

    // set the driver strategy

    config.setDriver(ds.getDriverClass());

    config.setDriverStrategy(ds);

    if (node.getComparator1() != null) {

      config.setDriverComparator(node.getComparator1(), 0);

    }

    if (node.getComparator2() != null) {

      config.setDriverComparator(node.getComparator2(), 1);

    }

    if (node.getPairComparator() != null) {

      config.setDriverPairComparator(node.getPairComparator());

    }

   

    // assign memory, file-handles, etc.

    assignDriverResources(node, config);

    return vertex;

  }

  private InputFormatVertex createDataSourceVertex(SourcePlanNode node) throws CompilerException {

    final InputFormatVertex vertex = new InputFormatVertex(node.getNodeName());

    final TaskConfig config = new TaskConfig(vertex.getConfiguration());

    vertex.setInvokableClass(DataSourceTask.class);

    // set user code

    config.setStubWrapper(node.getPactContract().getUserCodeWrapper());

    config.setStubParameters(node.getPactContract().getParameters());

    config.setOutputSerializer(node.getSerializer());

    return vertex;

  }

  private AbstractJobVertex createDataSinkVertex(SinkPlanNode node) throws CompilerException {

    final OutputFormatVertex vertex = new OutputFormatVertex(node.getNodeName());

    final TaskConfig config = new TaskConfig(vertex.getConfiguration());

    vertex.setInvokableClass(DataSinkTask.class);

    vertex.getConfiguration().setInteger(DataSinkTask.DEGREE_OF_PARALLELISM_KEY, node.getDegreeOfParallelism());

    // set user code

    config.setStubWrapper(node.getPactContract().getUserCodeWrapper());

    config.setStubParameters(node.getPactContract().getParameters());

    return vertex;

  }

 

  private AbstractJobVertex createBulkIterationHead(BulkPartialSolutionPlanNode pspn) {

    // get the bulk iteration that corresponds to this partial solution node

    final BulkIterationPlanNode iteration = pspn.getContainingIterationNode();

   

    // check whether we need an individual vertex for the partial solution, or whether we

    // attach ourselves to the vertex of the parent node. We can combine the head with a node of

    // the step function, if

    // 1) There is one parent that the partial solution connects to via a forward pattern and no

    //    local strategy

    // 2) DOP and the number of subtasks per instance does not change

    // 3) That successor is not a union

    // 4) That successor is not itself the last node of the step function

    // 5) There is no local strategy on the edge for the initial partial solution, as

    //    this translates to a local strategy that would only be executed in the first iteration

   

    final boolean merge;

    if (mergeIterationAuxTasks && pspn.getOutgoingChannels().size() == 1) {

      final Channel c = pspn.getOutgoingChannels().get(0);

      final PlanNode successor = c.getTarget();

      merge = c.getShipStrategy() == ShipStrategyType.FORWARD &&

          c.getLocalStrategy() == LocalStrategy.NONE &&

          c.getTempMode() == TempMode.NONE &&

          successor.getDegreeOfParallelism() == pspn.getDegreeOfParallelism() &&

          !(successor instanceof NAryUnionPlanNode) &&

          successor != iteration.getRootOfStepFunction() &&

          iteration.getInput().getLocalStrategy() == LocalStrategy.NONE;

    } else {

      merge = false;

    }

   

    // create or adopt the head vertex

    final AbstractJobVertex toReturn;

    final AbstractJobVertex headVertex;

    final TaskConfig headConfig;

    if (merge) {

      final PlanNode successor = pspn.getOutgoingChannels().get(0).getTarget();

      headVertex = (AbstractJobVertex) this.vertices.get(successor);

     

      if (headVertex == null) {

        throw new CompilerException(

          "Bug: Trying to merge solution set with its sucessor, but successor has not been created.");

      }

     

      // reset the vertex type to iteration head

      headVertex.setInvokableClass(IterationHeadPactTask.class);

      headConfig = new TaskConfig(headVertex.getConfiguration());

      toReturn = null;

    } else {

      // instantiate the head vertex and give it a no-op driver as the driver strategy.

      // everything else happens in the post visit, after the input (the initial partial solution)

      // is connected.

      headVertex = new AbstractJobVertex("PartialSolution ("+iteration.getNodeName()+")");

      headVertex.setInvokableClass(IterationHeadPactTask.class);

      headConfig = new TaskConfig(headVertex.getConfiguration());

      headConfig.setDriver(NoOpDriver.class);

      toReturn = headVertex;

    }

   

    // create the iteration descriptor and the iteration to it

    IterationDescriptor descr = this.iterations.get(iteration);

    if (descr == null) {

      throw new CompilerException("Bug: Iteration descriptor was not created at when translating the iteration node.");

    }

    descr.setHeadTask(headVertex, headConfig);

   

    return toReturn;

  }

 

  private AbstractJobVertex createWorksetIterationHead(WorksetPlanNode wspn) {

    // get the bulk iteration that corresponds to this partial solution node

    final WorksetIterationPlanNode iteration = wspn.getContainingIterationNode();

   

    // check whether we need an individual vertex for the partial solution, or whether we

    // attach ourselves to the vertex of the parent node. We can combine the head with a node of

    // the step function, if

    // 1) There is one parent that the partial solution connects to via a forward pattern and no

    //    local strategy

    // 2) DOP and the number of subtasks per instance does not change

    // 3) That successor is not a union

    // 4) That successor is not itself the last node of the step function

    // 5) There is no local strategy on the edge for the initial workset, as

    //    this translates to a local strategy that would only be executed in the first superstep

   

    final boolean merge;

    if (mergeIterationAuxTasks && wspn.getOutgoingChannels().size() == 1) {

      final Channel c = wspn.getOutgoingChannels().get(0);

      final PlanNode successor = c.getTarget();

      merge = c.getShipStrategy() == ShipStrategyType.FORWARD &&

          c.getLocalStrategy() == LocalStrategy.NONE &&

          c.getTempMode() == TempMode.NONE &&

          successor.getDegreeOfParallelism() == wspn.getDegreeOfParallelism() &&

          !(successor instanceof NAryUnionPlanNode) &&

          successor != iteration.getNextWorkSetPlanNode() &&

          iteration.getInitialWorksetInput().getLocalStrategy() == LocalStrategy.NONE;

    } else {

      merge = false;

    }

   

    // create or adopt the head vertex

    final AbstractJobVertex toReturn;

    final AbstractJobVertex headVertex;

    final TaskConfig headConfig;

    if (merge) {

      final PlanNode successor = wspn.getOutgoingChannels().get(0).getTarget();

      headVertex = (AbstractJobVertex) this.vertices.get(successor);

     

      if (headVertex == null) {

        throw new CompilerException(

          "Bug: Trying to merge solution set with its sucessor, but successor has not been created.");

      }

     

      // reset the vertex type to iteration head

      headVertex.setInvokableClass(IterationHeadPactTask.class);

      headConfig = new TaskConfig(headVertex.getConfiguration());

      toReturn = null;

    } else {

      // instantiate the head vertex and give it a no-op driver as the driver strategy.

      // everything else happens in the post visit, after the input (the initial partial solution)

      // is connected.

      headVertex = new AbstractJobVertex("IterationHead("+iteration.getNodeName()+")");

      headVertex.setInvokableClass(IterationHeadPactTask.class);

      headConfig = new TaskConfig(headVertex.getConfiguration());

      headConfig.setDriver(NoOpDriver.class);

      toReturn = headVertex;

    }

   

    headConfig.setSolutionSetUnmanaged(iteration.getIterationNode().getIterationContract().isSolutionSetUnManaged());

   

    // create the iteration descriptor and the iteration to it

    IterationDescriptor descr = this.iterations.get(iteration);

    if (descr == null) {

      throw new CompilerException("Bug: Iteration descriptor was not created at when translating the iteration node.");

    }

    descr.setHeadTask(headVertex, headConfig);

   

    return toReturn;

  }

 

  private void assignDriverResources(PlanNode node, TaskConfig config) {

    final double relativeMem = node.getRelativeMemoryPerSubTask();

    if (relativeMem > 0) {

      config.setRelativeMemoryDriver(relativeMem);

      config.setFilehandlesDriver(this.defaultMaxFan);

      config.setSpillingThresholdDriver(this.defaultSortSpillingThreshold);

    }

  }

 

  private void assignLocalStrategyResources(Channel c, TaskConfig config, int inputNum) {

    if (c.getRelativeMemoryLocalStrategy() > 0) {

      config.setRelativeMemoryInput(inputNum, c.getRelativeMemoryLocalStrategy());

      config.setFilehandlesInput(inputNum, this.defaultMaxFan);

      config.setSpillingThresholdInput(inputNum, this.defaultSortSpillingThreshold);

    }

  }

  // ------------------------------------------------------------------------

  // Connecting Vertices

  // ------------------------------------------------------------------------

  /**

   * NOTE: The channel for global and local strategies are different if we connect a union. The global strategy

   * channel is then the channel into the union node, the local strategy channel the one from the union to the

   * actual target operator.

   *

   * @param channel

   * @param inputNumber

   * @param sourceVertex

   * @param sourceConfig

   * @param targetVertex

   * @param targetConfig

   * @param isBroadcast

   * @throws CompilerException

   */

  private DistributionPattern connectJobVertices(Channel channel, int inputNumber,

      final AbstractJobVertex sourceVertex, final TaskConfig sourceConfig,

      final AbstractJobVertex targetVertex, final TaskConfig targetConfig, boolean isBroadcast)

  throws CompilerException

  {

    // ------------ connect the vertices to the job graph --------------

    final DistributionPattern distributionPattern;

    switch (channel.getShipStrategy()) {

      case FORWARD:

        distributionPattern = DistributionPattern.POINTWISE;

        break;

      case PARTITION_RANDOM:

      case BROADCAST:

      case PARTITION_HASH:

      case PARTITION_RANGE:

      case PARTITION_FORCED_REBALANCE:

        distributionPattern = DistributionPattern.BIPARTITE;

        break;

      default:

        throw new RuntimeException("Unknown runtime ship strategy: " + channel.getShipStrategy());

    }

   

    targetVertex.connectNewDataSetAsInput(sourceVertex, distributionPattern);

   

    // -------------- configure the source task's ship strategy strategies in task config --------------

    final int outputIndex = sourceConfig.getNumOutputs();

    sourceConfig.addOutputShipStrategy(channel.getShipStrategy());

    if (outputIndex == 0) {

      sourceConfig.setOutputSerializer(channel.getSerializer());

    }

    if (channel.getShipStrategyComparator() != null) {

      sourceConfig.setOutputComparator(channel.getShipStrategyComparator(), outputIndex);

    }

   

    if (channel.getShipStrategy() == ShipStrategyType.PARTITION_RANGE) {

     

      final DataDistribution dataDistribution = channel.getDataDistribution();

      if(dataDistribution != null) {

        sourceConfig.setOutputDataDistribution(dataDistribution, outputIndex);

      } else {

        throw new RuntimeException("Range partitioning requires data distribution");

        // TODO: inject code and configuration for automatic histogram generation

      }

    }

//      final DataDistribution distri = ((GenericDataSink) targetContract).getDataDistribution();

//      if (distri != null) {

//        configForOutputShipStrategy.setOutputDataDistribution(distri);

//      }

//    }

   

    // ---------------- configure the receiver -------------------

    if (isBroadcast) {

      targetConfig.addBroadcastInputToGroup(inputNumber);

    } else {

      targetConfig.addInputToGroup(inputNumber);

    }

    return distributionPattern;

  }

 

  private void addLocalInfoFromChannelToConfig(Channel channel, TaskConfig config, int inputNum, boolean isBroadcastChannel) {

    // serializer

    if (isBroadcastChannel) {

      config.setBroadcastInputSerializer(channel.getSerializer(), inputNum);

     

      if (channel.getLocalStrategy() != LocalStrategy.NONE || (channel.getTempMode() != null && channel.getTempMode() != TempMode.NONE)) {

        throw new CompilerException("Found local strategy or temp mode on a broadcast variable channel.");

      } else {

        return;

      }

    } else {

      config.setInputSerializer(channel.getSerializer(), inputNum);

    }

   

    // local strategy

    if (channel.getLocalStrategy() != LocalStrategy.NONE) {

      config.setInputLocalStrategy(inputNum, channel.getLocalStrategy());

      if (channel.getLocalStrategyComparator() != null) {

        config.setInputComparator(channel.getLocalStrategyComparator(), inputNum);

      }

    }

   

    assignLocalStrategyResources(channel, config, inputNum);

   

    // materialization / caching

    if (channel.getTempMode() != null) {

      final TempMode tm = channel.getTempMode();

      boolean needsMemory = false;

      if (tm.breaksPipeline()) {

        config.setInputAsynchronouslyMaterialized(inputNum, true);

        needsMemory = true;

      }

      if (tm.isCached()) {

        config.setInputCached(inputNum, true);

        needsMemory = true;

      }

     

      if (needsMemory) {

        // sanity check

        if (tm == null || tm == TempMode.NONE || channel.getRelativeTempMemory() <= 0) {

          throw new CompilerException("Bug in compiler: Inconsistent description of input materialization.");

        }

        config.setRelativeInputMaterializationMemory(inputNum, channel.getRelativeTempMemory());

      }

    }

  }

 

  private void finalizeBulkIteration(IterationDescriptor descr) {

   

    final BulkIterationPlanNode bulkNode = (BulkIterationPlanNode) descr.getIterationNode();

    final AbstractJobVertex headVertex = descr.getHeadTask();

    final TaskConfig headConfig = new TaskConfig(headVertex.getConfiguration());

    final TaskConfig headFinalOutputConfig = descr.getHeadFinalResultConfig();

   

    // ------------ finalize the head config with the final outputs and the sync gate ------------

    final int numStepFunctionOuts = headConfig.getNumOutputs();

    final int numFinalOuts = headFinalOutputConfig.getNumOutputs();

   

    if (numStepFunctionOuts == 0) {

      throw new CompilerException("The iteration has no operation inside the step function.");

    }

   

    headConfig.setIterationHeadFinalOutputConfig(headFinalOutputConfig);

    headConfig.setIterationHeadIndexOfSyncOutput(numStepFunctionOuts + numFinalOuts);

    final double relativeMemForBackChannel = bulkNode.getRelativeMemoryPerSubTask();

    if (relativeMemForBackChannel <= 0) {

      throw new CompilerException("Bug: No memory has been assigned to the iteration back channel.");

    }

    headConfig.setRelativeBackChannelMemory(relativeMemForBackChannel);

   

    // --------------------------- create the sync task ---------------------------

    final AbstractJobVertex sync = new AbstractJobVertex("Sync(" + bulkNode.getNodeName() + ")");

    sync.setInvokableClass(IterationSynchronizationSinkTask.class);

    sync.setParallelism(1);

    this.auxVertices.add(sync);

   

    final TaskConfig syncConfig = new TaskConfig(sync.getConfiguration());

    syncConfig.setGateIterativeWithNumberOfEventsUntilInterrupt(0, headVertex.getParallelism());

    // set the number of iteration / convergence criterion for the sync

    final int maxNumIterations = bulkNode.getIterationNode().getIterationContract().getMaximumNumberOfIterations();

    if (maxNumIterations < 1) {

      throw new CompilerException("Cannot create bulk iteration with unspecified maximum number of iterations.");

    }

    syncConfig.setNumberOfIterations(maxNumIterations);

   

    // connect the sync task

    sync.connectNewDataSetAsInput(headVertex, DistributionPattern.POINTWISE);

   

    // ----------------------------- create the iteration tail ------------------------------

   

    final PlanNode rootOfTerminationCriterion = bulkNode.getRootOfTerminationCriterion();

    final PlanNode rootOfStepFunction = bulkNode.getRootOfStepFunction();

    final TaskConfig tailConfig;

   

    AbstractJobVertex rootOfStepFunctionVertex = (AbstractJobVertex) this.vertices.get(rootOfStepFunction);

    if (rootOfStepFunctionVertex == null) {

      // last op is chained

      final TaskInChain taskInChain = this.chainedTasks.get(rootOfStepFunction);

      if (taskInChain == null) {

        throw new CompilerException("Bug: Tail of step function not found as vertex or chained task.");

      }

      rootOfStepFunctionVertex = (AbstractJobVertex) taskInChain.getContainingVertex();

      // the fake channel is statically typed to pact record. no data is sent over this channel anyways.

      tailConfig = taskInChain.getTaskConfig();

    } else {

      tailConfig = new TaskConfig(rootOfStepFunctionVertex.getConfiguration());

    }

   

    tailConfig.setIsWorksetUpdate();

   

    // No following termination criterion

    if (rootOfStepFunction.getOutgoingChannels().isEmpty()) {

     

      rootOfStepFunctionVertex.setInvokableClass(IterationTailPactTask.class);

     

      tailConfig.setOutputSerializer(bulkNode.getSerializerForIterationChannel());

    }

   

   

    // create the fake output task for termination criterion, if needed

    final TaskConfig tailConfigOfTerminationCriterion;

    // If we have a termination criterion and it is not an intermediate node

    if(rootOfTerminationCriterion != null && rootOfTerminationCriterion.getOutgoingChannels().isEmpty()) {

      AbstractJobVertex rootOfTerminationCriterionVertex = (AbstractJobVertex) this.vertices.get(rootOfTerminationCriterion);

     

     

      if (rootOfTerminationCriterionVertex == null) {

        // last op is chained

        final TaskInChain taskInChain = this.chainedTasks.get(rootOfTerminationCriterion);

        if (taskInChain == null) {

          throw new CompilerException("Bug: Tail of termination criterion not found as vertex or chained task.");

        }

        rootOfTerminationCriterionVertex = (AbstractJobVertex) taskInChain.getContainingVertex();

        // the fake channel is statically typed to pact record. no data is sent over this channel anyways.

        tailConfigOfTerminationCriterion = taskInChain.getTaskConfig();

      } else {

        tailConfigOfTerminationCriterion = new TaskConfig(rootOfTerminationCriterionVertex.getConfiguration());

      }

     

      rootOfTerminationCriterionVertex.setInvokableClass(IterationTailPactTask.class);

      // Hack

      tailConfigOfTerminationCriterion.setIsSolutionSetUpdate();

      tailConfigOfTerminationCriterion.setOutputSerializer(bulkNode.getSerializerForIterationChannel());

     

      // tell the head that it needs to wait for the solution set updates

      headConfig.setWaitForSolutionSetUpdate();

    }

   

    // ------------------- register the aggregators -------------------

    AggregatorRegistry aggs = bulkNode.getIterationNode().getIterationContract().getAggregators();

    Collection<AggregatorWithName<?>> allAggregators = aggs.getAllRegisteredAggregators();

   

    headConfig.addIterationAggregators(allAggregators);

    syncConfig.addIterationAggregators(allAggregators);

   

    String convAggName = aggs.getConvergenceCriterionAggregatorName();

    ConvergenceCriterion<?> convCriterion = aggs.getConvergenceCriterion();

   

    if (convCriterion != null || convAggName != null) {

      if (convCriterion == null) {

        throw new CompilerException("Error: Convergence criterion aggregator set, but criterion is null.");

      }

      if (convAggName == null) {

        throw new CompilerException("Error: Aggregator convergence criterion set, but aggregator is null.");

      }

     

      syncConfig.setConvergenceCriterion(convAggName, convCriterion);

    }

  }

 

  private void finalizeWorksetIteration(IterationDescriptor descr) {

    final WorksetIterationPlanNode iterNode = (WorksetIterationPlanNode) descr.getIterationNode();

    final AbstractJobVertex headVertex = descr.getHeadTask();

    final TaskConfig headConfig = new TaskConfig(headVertex.getConfiguration());

    final TaskConfig headFinalOutputConfig = descr.getHeadFinalResultConfig();

   

    // ------------ finalize the head config with the final outputs and the sync gate ------------

    {

      final int numStepFunctionOuts = headConfig.getNumOutputs();

      final int numFinalOuts = headFinalOutputConfig.getNumOutputs();

     

      if (numStepFunctionOuts == 0) {

        throw new CompilerException("The workset iteration has no operation on the workset inside the step function.");

      }

     

      headConfig.setIterationHeadFinalOutputConfig(headFinalOutputConfig);

      headConfig.setIterationHeadIndexOfSyncOutput(numStepFunctionOuts + numFinalOuts);

      final double relativeMemory = iterNode.getRelativeMemoryPerSubTask();

      if (relativeMemory <= 0) {

        throw new CompilerException("Bug: No memory has been assigned to the workset iteration.");

      }

     

      headConfig.setIsWorksetIteration();

      headConfig.setRelativeBackChannelMemory(relativeMemory / 2);

      headConfig.setRelativeSolutionSetMemory(relativeMemory / 2);