org.apache.flink.graph.spargel

Class GatherFunction<K,VV,Message>

java.lang.Object

org.apache.flink.graph.spargel.GatherFunction<K,VV,Message>

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

ConnectedComponents.CCUpdater, IncrementalSSSP.VertexDistanceUpdater, LabelPropagation.UpdateVertexLabel, PageRank.VertexRankUpdater, SingleSourceShortestPaths.VertexDistanceUpdater

public abstract class GatherFunction<K,VV,Message>
extends Object
implements Serializable

This class must be extended by functions that compute the state of the vertex depending on the old state and the incoming messages. The central method is updateVertex(Vertex, MessageIterator), which is invoked once per vertex per superstep. <K> The vertex key type. <VV> The vertex value type. <Message> The message type.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GatherFunction()

Method Summary

Modifier and Type	Method and Description
<T> Collection<T>	getBroadcastSet(String name) Gets the broadcast data set registered under the given name.
long	getInDegree() Retrieves the vertex in-degree (number of in-coming edges).
<T extends Aggregator<?>> T	getIterationAggregator(String name) Gets the iteration aggregator registered under the given name.
long	getNumberOfVertices() Retrieves the number of vertices in the graph.
long	getOutDegree() Retrieve the vertex out-degree (number of out-going edges).
<T extends Value> T	getPreviousIterationAggregate(String name) Get the aggregated value that an aggregator computed in the previous iteration.
int	getSuperstepNumber() Gets the number of the superstep, starting at 1.
void	postSuperstep() This method is executed once per superstep after the gather function has been invoked for each vertex.
void	preSuperstep() This method is executed once per superstep before the gather function is invoked for each vertex.
void	setNewVertexValue(VV newValue) Sets the new value of this vertex.
abstract void	updateVertex(Vertex<K,VV> vertex, MessageIterator<Message> inMessages) This method is invoked once per vertex per superstep.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GatherFunction

public GatherFunction()

Method Detail

getNumberOfVertices

public long getNumberOfVertices()

Retrieves the number of vertices in the graph.

Returns:

the number of vertices if the IterationConfiguration.setOptNumVertices(boolean) option has been set; -1 otherwise.

updateVertex

public abstract void updateVertex(Vertex<K,VV> vertex,
                                  MessageIterator<Message> inMessages)
                           throws Exception

This method is invoked once per vertex per superstep. It receives the current state of the vertex, as well as the incoming messages. It may set a new vertex state via setNewVertexValue(Object). If the vertex state is changed, it will trigger the sending of messages via the ScatterFunction.

Parameters:

vertex - The vertex.

inMessages - The incoming messages to this vertex.

Throws:

Exception - The computation may throw exceptions, which causes the superstep to fail.

preSuperstep

public void preSuperstep()
                  throws Exception

This method is executed once per superstep before the gather function is invoked for each vertex.

Throws:

Exception - Exceptions in the pre-superstep phase cause the superstep to fail.

postSuperstep

public void postSuperstep()
                   throws Exception

This method is executed once per superstep after the gather function has been invoked for each vertex.

Throws:

Exception - Exceptions in the post-superstep phase cause the superstep to fail.

setNewVertexValue

public void setNewVertexValue(VV newValue)

Sets the new value of this vertex. Setting a new value triggers the sending of outgoing messages from this vertex.

This should be called at most once per updateVertex.

Parameters:

newValue - The new vertex value.

getSuperstepNumber

public int getSuperstepNumber()

Gets the number of the superstep, starting at 1.

Returns:

The number of the current superstep.

getIterationAggregator

public <T extends Aggregator<?>> T getIterationAggregator(String name)

Gets the iteration aggregator registered under the given name. The iteration aggregator combines all aggregates globally once per superstep and makes them available in the next superstep.

Parameters:

name - The name of the aggregator.

Returns:

The aggregator registered under this name, or null, if no aggregator was registered.

getPreviousIterationAggregate

public <T extends Value> T getPreviousIterationAggregate(String name)

Get the aggregated value that an aggregator computed in the previous iteration.

Parameters:

name - The name of the aggregator.

Returns:

The aggregated value of the previous iteration.

getBroadcastSet

public <T> Collection<T> getBroadcastSet(String name)

Gets the broadcast data set registered under the given name. Broadcast data sets are available on all parallel instances of a function. They can be registered via ScatterGatherConfiguration.addBroadcastSetForGatherFunction(String, org.apache.flink.api.java.DataSet).

Parameters:

name - The name under which the broadcast set is registered.

Returns:

The broadcast data set.

getInDegree

public long getInDegree()

Retrieves the vertex in-degree (number of in-coming edges).

Returns:

The in-degree of this vertex

getOutDegree

public long getOutDegree()

Retrieve the vertex out-degree (number of out-going edges).

Returns:

The out-degree of this vertex