org.apache.flink.graph.spargel

Class ScatterFunction<K,VV,Message,EV>

java.lang.Object

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

Type Parameters:

K - The type of the vertex key (the vertex identifier).

VV - The type of the vertex value (the state of the vertex).

Message - The type of the message sent between vertices along the edges.

EV - The type of the values that are associated with the edges.

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

ConnectedComponents.CCMessenger, IncrementalSSSP.InvalidateMessenger, LabelPropagation.SendNewLabelToNeighbors, PageRank.RankMessenger, SingleSourceShortestPaths.MinDistanceMessenger

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

The base class for functions that produce messages between vertices as a part of a ScatterGatherIteration.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ScatterFunction()

Method Summary

Modifier and Type	Method and Description
<T> Collection<T>	getBroadcastSet(String name) Gets the broadcast data set registered under the given name.
EdgeDirection	getDirection() Retrieves the edge direction in which messages are propagated in the scatter-gather iteration.
Iterable<Edge<K,EV>>	getEdges() Gets an Iterable with all edges.
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 scatter function has been invoked for each vertex.
void	preSuperstep() This method is executed once per superstep before the scatter function is invoked for each vertex.
abstract void	sendMessages(Vertex<K,VV> vertex) This method is invoked once per superstep for each vertex that was changed in that superstep.
void	sendMessageTo(K target, Message m) Sends the given message to the vertex identified by the given key.
void	sendMessageToAllNeighbors(Message m) Sends the given message to all vertices that are targets of an edge of the changed vertex.

Methods inherited from class java.lang.Object

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

Constructor Detail

ScatterFunction

public ScatterFunction()

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.

getDirection

public EdgeDirection getDirection()

Retrieves the edge direction in which messages are propagated in the scatter-gather iteration.

Returns:

the messaging EdgeDirection

sendMessages

public abstract void sendMessages(Vertex<K,VV> vertex)
                           throws Exception

This method is invoked once per superstep for each vertex that was changed in that superstep. It needs to produce the messages that will be received by vertices in the next superstep.

Parameters:

vertex - The vertex that was changed.

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 scatter 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 scatter function has been invoked for each vertex.

Throws:

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

getEdges

public Iterable<Edge<K,EV>> getEdges()

Gets an Iterable with all edges. This method is mutually exclusive with sendMessageToAllNeighbors(Object) and may be called only once.

If the EdgeDirection is OUT (default), then this iterator contains outgoing edges.

If the EdgeDirection is IN, then this iterator contains incoming edges.

If the EdgeDirection is ALL, then this iterator contains both outgoing and incoming edges.

Returns:

An iterator with all edges.

sendMessageToAllNeighbors

public void sendMessageToAllNeighbors(Message m)

Sends the given message to all vertices that are targets of an edge of the changed vertex. This method is mutually exclusive to the method getEdges() and may be called only once.

If the EdgeDirection is OUT (default), the message will be sent to out-neighbors.

If the EdgeDirection is IN, the message will be sent to in-neighbors.

If the EdgeDirection is ALL, the message will be sent to all neighbors.

Parameters:

m - The message to send.

sendMessageTo

public void sendMessageTo(K target,
                          Message m)

Sends the given message to the vertex identified by the given key. If the target vertex does not exist, the next superstep will cause an exception due to a non-deliverable message.

Parameters:

target - The key (id) of the target vertex to message.

m - The message.

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.addBroadcastSetForScatterFunction(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