Class TraversalVertexProgram
- java.lang.Object
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- org.apache.tinkerpop.gremlin.process.computer.traversal.TraversalVertexProgram
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- All Implemented Interfaces:
Cloneable
,VertexProgram<TraverserSet<Object>>
public final class TraversalVertexProgram extends Object implements VertexProgram<TraverserSet<Object>>
TraversalVertexProgram
enables the evaluation of aTraversal
on aGraphComputer
. At the start of the computation, eachVertex
(orEdge
) is assigned a singleTraverser
. 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)
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
TraversalVertexProgram.Builder
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Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram
VertexProgram.Features
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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
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Fields inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram
VERTEX_PROGRAM
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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 ofMapReduce
jobs that are associated with theVertexProgram
.Set<MemoryComputeKey>
getMemoryComputeKeys()
TheMemory
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 theMessageScope
possibilities for a particular iteration of the vertex program.GraphComputer.Persist
getPreferredPersist()
GraphComputer.ResultGraph
getPreferredResultGraph()
PureTraversal<?,?>
getTraversal()
Get thePureTraversal
associated with the current instance of theTraversalVertexProgram
.Set<VertexComputeKey>
getVertexComputeKeys()
TheElement
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
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Methods inherited from interface org.apache.tinkerpop.gremlin.process.computer.VertexProgram
getTraverserRequirements
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Field Detail
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TRAVERSAL
public static final String TRAVERSAL
- See Also:
- Constant Field Values
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HALTED_TRAVERSERS
public static final String HALTED_TRAVERSERS
- See Also:
- Constant Field Values
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ACTIVE_TRAVERSERS
public static final String ACTIVE_TRAVERSERS
- See Also:
- Constant Field Values
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MUTATED_MEMORY_KEYS
protected static final String MUTATED_MEMORY_KEYS
- See Also:
- Constant Field Values
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Method Detail
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getTraversal
public PureTraversal<?,?> getTraversal()
Get thePureTraversal
associated with the current instance of theTraversalVertexProgram
.- Returns:
- the pure traversal of the instantiated program
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loadHaltedTraversers
public static <R> TraverserSet<R> loadHaltedTraversers(org.apache.commons.configuration2.Configuration configuration)
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storeHaltedTraversers
public static <R> void storeHaltedTraversers(org.apache.commons.configuration2.Configuration configuration, TraverserSet<R> haltedTraversers)
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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 interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
graph
- the graph that the VertexProgram will run againstconfiguration
- the configuration to load the state of the VertexProgram from.
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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 interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
configuration
- the configuration to store the state of the VertexProgram in.
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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 theGraphComputer
and as such, is not called for each vertex. During this stage, theMemory
should be initialized to to its "start state."- Specified by:
setup
in interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
memory
- The global memory of the GraphComputer
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getMessageScopes
public Set<MessageScope> getMessageScopes(Memory memory)
Description copied from interface:VertexProgram
This method returns all theMessageScope
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 interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
memory
- an immutable form of theMemory
- Returns:
- all possible message scopes during said vertex program iteration
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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 theMemory
is read, it is according to the aggregated state yielded in the previous iteration. When theMemory
is written, the data will be aggregated at the end of the iteration for reading in the next iteration.- Specified by:
execute
in interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
vertex
- theVertex
to execute theVertexProgram
onmessenger
- the messenger that moves data between verticesmemory
- the shared state between all vertices in the computation
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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 theGraphComputer
and as such, is not called for eachVertex
. TheMemory
maintains the aggregated data from the last execute() iteration.- Specified by:
terminate
in interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
memory
- The global memory of theGraphComputer
- Returns:
- whether or not to halt the computation
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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 theVertexProgram.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 interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
memory
- The memory at the start of the iteration.
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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 theVertexProgram.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 interfaceVertexProgram<TraverserSet<Object>>
- Parameters:
memory
- The memory at the end of the iteration.
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getVertexComputeKeys
public Set<VertexComputeKey> getVertexComputeKeys()
Description copied from interface:VertexProgram
TheElement
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 interfaceVertexProgram<TraverserSet<Object>>
- Returns:
- the set of element keys that will be mutated during the vertex program's execution
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getMemoryComputeKeys
public Set<MemoryComputeKey> getMemoryComputeKeys()
Description copied from interface:VertexProgram
TheMemory
keys that will be used during the computation. These are the only keys that can be read or written throughout the life of theGraphComputer
. The default is an empty set.- Specified by:
getMemoryComputeKeys
in interfaceVertexProgram<TraverserSet<Object>>
- Returns:
- the set of memory keys that will be read/written
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getMapReducers
public Set<MapReduce> getMapReducers()
Description copied from interface:VertexProgram
The set ofMapReduce
jobs that are associated with theVertexProgram
. This is not necessarily the exhaustive list over the life of theGraphComputer
. 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 interfaceVertexProgram<TraverserSet<Object>>
- Returns:
- the set of
MapReduce
jobs associated with thisVertexProgram
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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 interfaceVertexProgram<TraverserSet<Object>>
- Returns:
- A optional denoting whether or not their is a message combine associated with the vertex program.
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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 theVertexProgram.storeState(org.apache.commons.configuration2.Configuration)
andVertexProgram.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 interfaceVertexProgram<TraverserSet<Object>>
- Overrides:
clone
in classObject
- Returns:
- A clone of the VertexProgram object
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getPreferredResultGraph
public GraphComputer.ResultGraph getPreferredResultGraph()
- Specified by:
getPreferredResultGraph
in interfaceVertexProgram<TraverserSet<Object>>
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getPreferredPersist
public GraphComputer.Persist getPreferredPersist()
- Specified by:
getPreferredPersist
in interfaceVertexProgram<TraverserSet<Object>>
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getFeatures
public VertexProgram.Features getFeatures()
- Specified by:
getFeatures
in interfaceVertexProgram<TraverserSet<Object>>
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build
public static TraversalVertexProgram.Builder build()
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