org.apache.flink.graph.pregel

Class ComputeFunction<K,VV,EV,Message>

java.lang.Object

org.apache.flink.graph.pregel.ComputeFunction<K,VV,EV,Message>

Type Parameters:

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

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

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

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

All Implemented Interfaces:

Serializable

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

The base class for the message-passing functions between vertices as a part of a VertexCentricIteration.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ComputeFunction()

Method Summary

Modifier and Type	Method and Description
abstract void	compute(Vertex<K,VV> vertex, MessageIterator<Message> messages) This method is invoked once per superstep, for each active vertex.
<T> Collection<T>	getBroadcastSet(String name) Gets the broadcast data set registered under the given name.
Iterable<Edge<K,EV>>	getEdges() Gets an Iterable with all out-going edges.
<T extends org.apache.flink.api.common.aggregators.Aggregator<?>> T	getIterationAggregator(String name) Gets the iteration aggregator registered under the given name.
<T extends org.apache.flink.types.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 vertex update function has been invoked for each vertex.
void	preSuperstep() This method is executed once per superstep before the vertex update function is invoked for each vertex.
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 adjacent to the changed vertex.
void	setNewVertexValue(VV newValue) Sets the new value of this vertex.

Methods inherited from class java.lang.Object

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

Constructor Detail

ComputeFunction

public ComputeFunction()

Method Detail

compute

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

This method is invoked once per superstep, for each active vertex. A vertex is active during a superstep, if at least one message was produced for it, in the previous superstep. During the first superstep, all vertices are active.

This method can iterate over all received messages, set the new vertex value, and send messages to other vertices (which will be delivered in the next superstep).

Parameters:

vertex - The vertex executing this function

messages - The messages that were sent to this vertex in the previous superstep

Throws:

Exception

preSuperstep

public void preSuperstep()
                  throws Exception

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

Throws:

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

getEdges

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

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

Returns:

An iterator with all edges.

sendMessageToAllNeighbors

public final void sendMessageToAllNeighbors(Message m)

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

Parameters:

m - The message to send.

sendMessageTo

public final 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.

setNewVertexValue

public final void setNewVertexValue(VV newValue)

Sets the new value of this vertex.

This should be called at most once per ComputeFunction.

Parameters:

newValue - The new vertex value.

getSuperstepNumber

public final int getSuperstepNumber()

Gets the number of the superstep, starting at 1.

Returns:

The number of the current superstep.

getIterationAggregator

public final <T extends org.apache.flink.api.common.aggregators.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 final <T extends org.apache.flink.types.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 final <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 VertexCentricConfiguration.addBroadcastSet(String, DataSet).

Parameters:

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

Returns:

The broadcast data set.