java.lang.Object
- org.apache.tinkerpop.gremlin.process.computer.traversal.TraversalVertexProgram

All Implemented Interfaces:

Cloneable, VertexProgram<TraverserSet<Object>>
```
public final class TraversalVertexProgram
extends Object
implements VertexProgram<TraverserSet<Object>>
```
TraversalVertexProgram enables the evaluation of a Traversal on a GraphComputer. At the start of the computation, each Vertex (or Edge) is assigned a single Traverser. For each traverser that is local to the vertex, the vertex looks up its current location in the traversal and processes that step. If the outputted traverser of the step references a local structure on the vertex (e.g. the vertex, an incident edge, its properties, or an arbitrary object), then the vertex continues to compute the next traverser. If the traverser references another location in the graph, then the traverser is sent to that location in the graph via a message. The messages of TraversalVertexProgram are traversers. This continues until all traversers in the computation have halted.

Author:

Marko A. Rodriguez (http://markorodriguez.com)

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class TraversalVertexProgram.Builder
- Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram
  VertexProgram.Features

Field Summary

Fields
Modifier and Type Field Description

static String ACTIVE_TRAVERSERS

static String HALTED_TRAVERSERS

protected static String MUTATED_MEMORY_KEYS

static String TRAVERSAL
- Fields inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram
  VERTEX_PROGRAM

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static TraversalVertexProgram.Builder`	`build()`
`TraversalVertexProgram`	`clone()`	When multiple workers on a single machine need VertexProgram instances, it is possible to use clone.
`void`	`execute(Vertex vertex, Messenger<TraverserSet<Object>> messenger, Memory memory)`	This method denotes the main body of the computation and is executed on each vertex in the graph.
`VertexProgram.Features`	`getFeatures()`
`Set<MapReduce>`	`getMapReducers()`	The set of `MapReduce` jobs that are associated with the `VertexProgram`.
`Set<MemoryComputeKey>`	`getMemoryComputeKeys()`	The `Memory` keys that will be used during the computation.
`Optional<MessageCombiner<TraverserSet<Object>>>`	`getMessageCombiner()`	Combine the messages in route to a particular vertex.
`Set<MessageScope>`	`getMessageScopes(Memory memory)`	This method returns all the `MessageScope` possibilities for a particular iteration of the vertex program.
`GraphComputer.Persist`	`getPreferredPersist()`
`GraphComputer.ResultGraph`	`getPreferredResultGraph()`
`PureTraversal<?,?>`	`getTraversal()`	Get the `PureTraversal` associated with the current instance of the `TraversalVertexProgram`.
`Set<VertexComputeKey>`	`getVertexComputeKeys()`	The `Element` properties that will be mutated during the computation.
`static <R> TraverserSet<R>`	`loadHaltedTraversers(org.apache.commons.configuration2.Configuration configuration)`
`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.
`void`	`setup(Memory memory)`	The method is called at the beginning of the computation.
`static <R> void`	`storeHaltedTraversers(org.apache.commons.configuration2.Configuration configuration, TraverserSet<R> haltedTraversers)`
`void`	`storeState(org.apache.commons.configuration2.Configuration configuration)`	When it is necessary to store the state of the VertexProgram, this method is called.
`boolean`	`terminate(Memory memory)`	The method is called at the end of each iteration to determine if the computation is complete.
`String`	`toString()`
`void`	`workerIterationEnd(Memory memory)`	This method is called at the end of each iteration of each "computational chunk." The set of vertices in the graph are typically not processed with full parallelism.
`void`	`workerIterationStart(Memory memory)`	This method is called at the start of each iteration of each "computational chunk." The set of vertices in the graph are typically not processed with full parallelism.

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram
getTraverserRequirements

- Field Detail
  - TRAVERSAL
```
public static final String TRAVERSAL
```
    See Also:
    
    Constant Field Values
  - HALTED_TRAVERSERS
```
public static final String HALTED_TRAVERSERS
```
    See Also:
    
    Constant Field Values
  - ACTIVE_TRAVERSERS
```
public static final String ACTIVE_TRAVERSERS
```
    See Also:
    
    Constant Field Values
  - MUTATED_MEMORY_KEYS
```
protected static final String MUTATED_MEMORY_KEYS
```
    See Also:
    
    Constant Field Values
- Method Detail
  - getTraversal
```
public PureTraversal<?,?> getTraversal()
```
    Get the PureTraversal associated with the current instance of the TraversalVertexProgram.
    
    Returns:
    
    the pure traversal of the instantiated program
  - loadHaltedTraversers
```
public static <R> TraverserSet<R> loadHaltedTraversers(org.apache.commons.configuration2.Configuration configuration)
```
  - storeHaltedTraversers
```
public static <R> void storeHaltedTraversers(org.apache.commons.configuration2.Configuration configuration,
                                             TraverserSet<R> haltedTraversers)
```
  - loadState
```
public void loadState(Graph graph,
                      org.apache.commons.configuration2.Configuration configuration)
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    loadState in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    graph - the graph that the VertexProgram will run against
    
    configuration - the configuration to load the state of the VertexProgram from.
  - storeState
```
public void storeState(org.apache.commons.configuration2.Configuration configuration)
```
    Description copied from interface: VertexProgram
    
    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().
    
    Specified by:
    
    storeState in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    configuration - the configuration to store the state of the VertexProgram in.
  - setup
```
public void setup(Memory memory)
```
    Description copied from interface: VertexProgram
    
    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."
    
    Specified by:
    
    setup in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    memory - The global memory of the GraphComputer
  - getMessageScopes
```
public Set<MessageScope> getMessageScopes(Memory memory)
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    getMessageScopes in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    memory - an immutable form of the Memory
    
    Returns:
    
    all possible message scopes during said vertex program iteration
  - execute
```
public void execute(Vertex vertex,
                    Messenger<TraverserSet<Object>> messenger,
                    Memory memory)
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    execute in interface VertexProgram<TraverserSet<Object>>
    
    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
```
public boolean terminate(Memory memory)
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    terminate in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    memory - The global memory of the GraphComputer
    
    Returns:
    
    whether or not to halt the computation
  - workerIterationStart
```
public void workerIterationStart(Memory memory)
```
    Description copied from interface: VertexProgram
    
    This method is called at the start of each iteration of each "computational chunk." The set of vertices in the graph are typically not processed with full parallelism. The vertex set is split into subsets and a worker is assigned to call the VertexProgram.execute(org.apache.tinkerpop.gremlin.structure.Vertex, org.apache.tinkerpop.gremlin.process.computer.Messenger<M>, org.apache.tinkerpop.gremlin.process.computer.Memory) method. The default implementation is a no-op.
    
    Specified by:
    
    workerIterationStart in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    memory - The memory at the start of the iteration.
  - workerIterationEnd
```
public void workerIterationEnd(Memory memory)
```
    Description copied from interface: VertexProgram
    
    This method is called at the end of each iteration of each "computational chunk." The set of vertices in the graph are typically not processed with full parallelism. The vertex set is split into subsets and a worker is assigned to call the VertexProgram.execute(org.apache.tinkerpop.gremlin.structure.Vertex, org.apache.tinkerpop.gremlin.process.computer.Messenger<M>, org.apache.tinkerpop.gremlin.process.computer.Memory) method. The default implementation is a no-op.
    
    Specified by:
    
    workerIterationEnd in interface VertexProgram<TraverserSet<Object>>
    
    Parameters:
    
    memory - The memory at the end of the iteration.
  - getVertexComputeKeys
```
public Set<VertexComputeKey> getVertexComputeKeys()
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    getVertexComputeKeys in interface VertexProgram<TraverserSet<Object>>
    
    Returns:
    
    the set of element keys that will be mutated during the vertex program's execution
  - getMemoryComputeKeys
```
public Set<MemoryComputeKey> getMemoryComputeKeys()
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    getMemoryComputeKeys in interface VertexProgram<TraverserSet<Object>>
    
    Returns:
    
    the set of memory keys that will be read/written
  - getMapReducers
```
public Set<MapReduce> getMapReducers()
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    getMapReducers in interface VertexProgram<TraverserSet<Object>>
    
    Returns:
    
    the set of MapReduce jobs associated with this VertexProgram
  - getMessageCombiner
```
public Optional<MessageCombiner<TraverserSet<Object>>> getMessageCombiner()
```
    Description copied from interface: VertexProgram
    
    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.
    
    Specified by:
    
    getMessageCombiner in interface VertexProgram<TraverserSet<Object>>
    
    Returns:
    
    A optional denoting whether or not their is a message combine associated with the vertex program.
  - clone
```
public TraversalVertexProgram clone()
```
    Description copied from interface: VertexProgram
    
    When multiple workers on a single machine need VertexProgram instances, it is possible to use clone. This will provide a speedier way of generating instances, over the VertexProgram.storeState(org.apache.commons.configuration2.Configuration) and VertexProgram.loadState(org.apache.tinkerpop.gremlin.structure.Graph, org.apache.commons.configuration2.Configuration) model. The default implementation simply returns the object as it assumes that the VertexProgram instance is a stateless singleton.
    
    Specified by:
    
    clone in interface VertexProgram<TraverserSet<Object>>
    
    Overrides:
    
    clone in class Object
    
    Returns:
    
    A clone of the VertexProgram object
  - getPreferredResultGraph
```
public GraphComputer.ResultGraph getPreferredResultGraph()
```
    Specified by:
    
    getPreferredResultGraph in interface VertexProgram<TraverserSet<Object>>
  - getPreferredPersist
```
public GraphComputer.Persist getPreferredPersist()
```
    Specified by:
    
    getPreferredPersist in interface VertexProgram<TraverserSet<Object>>
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - getFeatures
```
public VertexProgram.Features getFeatures()
```
    Specified by:
    
    getFeatures in interface VertexProgram<TraverserSet<Object>>
  - build
```
public static TraversalVertexProgram.Builder build()
```

Modifier and Type	Field	Description
`static String`	`ACTIVE_TRAVERSERS`
`static String`	`HALTED_TRAVERSERS`
`protected static String`	`MUTATED_MEMORY_KEYS`
`static String`	`TRAVERSAL`

Class TraversalVertexProgram

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram

Field Summary

Fields inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram

Field Detail

TRAVERSAL

HALTED_TRAVERSERS

ACTIVE_TRAVERSERS

MUTATED_MEMORY_KEYS

Method Detail

getTraversal

loadHaltedTraversers

storeHaltedTraversers

loadState

storeState

setup

getMessageScopes

execute

terminate

workerIterationStart

workerIterationEnd

getVertexComputeKeys

getMemoryComputeKeys

getMapReducers

getMessageCombiner

clone

getPreferredResultGraph

getPreferredPersist

toString

getFeatures

build