Package org.apache.tinkerpop.gremlin.process.computer

Interface VertexProgram<M>

    • Method Detail

      • storeState

        default void storeState​(org.apache.commons.configuration2.Configuration configuration)
        When it is necessary to store the state of the VertexProgram, this method is called. This is typically required when the VertexProgram needs to be serialized to another machine. Note that what is stored is simply the instance/configuration state, not any processed data. The default implementation provided simply stores the VertexProgram class name for reflective reconstruction. It is typically a good idea to VertexProgram.super.storeState().
        Parameters:
        configuration - the configuration to store the state of the VertexProgram in.

      • loadState

        default void loadState​(Graph graph,
                       org.apache.commons.configuration2.Configuration configuration)
        When it is necessary to load the state of the VertexProgram, this method is called. This is typically required when the VertexProgram needs to be serialized to another machine. Note that what is loaded is simply the instance state, not any processed data.
        Parameters:
        graph - the graph that the VertexProgram will run against
        configuration - the configuration to load the state of the VertexProgram from.

      • setup

        void setup​(Memory memory)
        The method is called at the beginning of the computation. The method is global to the GraphComputer and as such, is not called for each vertex. During this stage, the Memory should be initialized to to its "start state."
        Parameters:
        memory - The global memory of the GraphComputer

      • execute

        void execute​(Vertex vertex,
             Messenger<M> messenger,
             Memory memory)
        This method denotes the main body of the computation and is executed on each vertex in the graph. This method is logically executed in parallel on all vertices in the graph. When the Memory is read, it is according to the aggregated state yielded in the previous iteration. When the Memory is written, the data will be aggregated at the end of the iteration for reading in the next iteration.
        Parameters:
        vertex - the Vertex to execute the VertexProgram on
        messenger - the messenger that moves data between vertices
        memory - the shared state between all vertices in the computation

      • terminate

        boolean terminate​(Memory memory)
        The method is called at the end of each iteration to determine if the computation is complete. The method is global to the GraphComputer and as such, is not called for each Vertex. The Memory maintains the aggregated data from the last execute() iteration.
        Parameters:
        memory - The global memory of the GraphComputer
        Returns:
        whether or not to halt the computation

      • getVertexComputeKeys

        default Set<VertexComputeKey> getVertexComputeKeys()
        The Element properties that will be mutated during the computation. All properties in the graph are readable, but only the keys specified here are writable. The default is an empty set.
        Returns:
        the set of element keys that will be mutated during the vertex program's execution

      • getMemoryComputeKeys

        default Set<MemoryComputeKey> getMemoryComputeKeys()
        The Memory keys that will be used during the computation. These are the only keys that can be read or written throughout the life of the GraphComputer. The default is an empty set.
        Returns:
        the set of memory keys that will be read/written

      • getMessageCombiner

        default Optional<MessageCombiner<M>> getMessageCombiner()
        Combine the messages in route to a particular vertex. Useful to reduce the amount of data transmitted over the wire. For example, instead of sending two objects that will ultimately be merged at the vertex destination, merge/combine into one and send that object. If no message combiner is provider, then no messages will be combined. Furthermore, it is not guaranteed the all messages in route to the vertex will be combined and thus, combiner-state should not be used. The result of the vertex program algorithm should be the same regardless of whether message combining is executed or not.
        Returns:
        A optional denoting whether or not their is a message combine associated with the vertex program.

      • getMessageScopes

        Set<MessageScope> getMessageScopes​(Memory memory)
        This method returns all the MessageScope possibilities for a particular iteration of the vertex program. The returned messages scopes are the scopes that will be used to send messages during the stated iteration. It is not a requirement that all stated messages scopes be used, just that it is possible that they be used during the iteration.
        Parameters:
        memory - an immutable form of the Memory
        Returns:
        all possible message scopes during said vertex program iteration

      • getMapReducers

        default Set<MapReduce> getMapReducers()
        The set of MapReduce jobs that are associated with the VertexProgram. This is not necessarily the exhaustive list over the life of the GraphComputer. If MapReduce jobs are declared by GraphComputer.mapReduce(), they are not contained in this set. The default is an empty set.
        Returns:
        the set of MapReduce jobs associated with this VertexProgram

      • getTraverserRequirements

        default Set<org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement> getTraverserRequirements()
        The traverser requirements that are needed when this VP is used as part of a traversal. The default is an empty set.
        Returns:
        the traverser requirements

      • createVertexProgram

        static <V extends VertexProgram> V createVertexProgram​(Graph graph,
                                                       org.apache.commons.configuration2.Configuration configuration)
        A helper method to construct a VertexProgram given the content of the supplied configuration. The class of the VertexProgram is read from the VERTEX_PROGRAM static configuration key. Once the VertexProgram is constructed, loadState(org.apache.tinkerpop.gremlin.structure.Graph, org.apache.commons.configuration2.Configuration) method is called with the provided graph and configuration.
        Type Parameters:
        V - The vertex program type
        Parameters:
        graph - The graph that the vertex program will execute against
        configuration - A configuration with requisite information to build a vertex program
        Returns:
        the newly constructed vertex program