Package org.neo4j.gds.msbfs

Class MultiSourceBFSAccessMethods

java.lang.Object

org.neo4j.gds.msbfs.MultiSourceBFSAccessMethods

public final class MultiSourceBFSAccessMethods
extends java.lang.Object

Multi Source Breadth First Search implemented as described in [1].

The benefit of running this MS-BFS instead of multiple execution of a regular BFS for every source is that the MS-BFS algorithm can collapse traversals that are the same for multiple nodes. If any two or more given BFSs would traverse the same nodes at the same iteration depth, the MS-BFS will traverse only once and group all sources for this traversal.

The consumer of this algorithm provides a callback function, the gets called with:

• the node id where the BFS traversal is at
• the depth or BFS iteration at which this node is traversed
• a lazily evaluated list of all source nodes that have arrived at this node at the same depth/iteration

The sources iterator is only valid during the execution of the callback and should not be stored.

We use a fixed ω (OMEGA) of 64, which allows us to implement the seen/visitNext bit sets as a packed long which improves memory locality as suggested in 4.1. of the paper. If the number of sources exceed 64, multiple instances of MS-BFS are run in parallel.

If the MS-BFS runs in parallel, the callback may be executed from multiple threads at the same time. The implementation should therefore be thread-safe.

[1]: The More the Merrier: Efficient Multi-Source Graph Traversal

Method Summary

Modifier and Type	Method	Description
static MultiSourceBFSAccessMethods	aggregatedNeighborProcessing(long nodeCount, org.neo4j.gds.api.RelationshipIterator relationships, BfsConsumer perNodeAction, long[] sourceNodes)
static MultiSourceBFSAccessMethods	aggregatedNeighborProcessingWithoutSourceNodes(long nodeCount, org.neo4j.gds.api.RelationshipIterator relationships, BfsConsumer perNodeAction)
static MultiSourceBFSAccessMethods	predecessorProcessing(org.neo4j.gds.api.Graph graph, BfsConsumer perNodeAction, BfsWithPredecessorConsumer perNeighborAction, long[] sourceNodes)
static MultiSourceBFSAccessMethods	predecessorProcessingWithoutSourceNodes(org.neo4j.gds.api.Graph graph, BfsConsumer perNodeAction, BfsWithPredecessorConsumer perNeighborAction)
void	run(int concurrency, java.util.concurrent.ExecutorService executor)	Runs MS-BFS, possibly in parallel.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

aggregatedNeighborProcessingWithoutSourceNodes

public static MultiSourceBFSAccessMethods aggregatedNeighborProcessingWithoutSourceNodes(long nodeCount,
                                                                                         org.neo4j.gds.api.RelationshipIterator relationships,
                                                                                         BfsConsumer perNodeAction)

aggregatedNeighborProcessing

public static MultiSourceBFSAccessMethods aggregatedNeighborProcessing(long nodeCount,
                                                                       org.neo4j.gds.api.RelationshipIterator relationships,
                                                                       BfsConsumer perNodeAction,
                                                                       long[] sourceNodes)

predecessorProcessingWithoutSourceNodes

public static MultiSourceBFSAccessMethods predecessorProcessingWithoutSourceNodes(org.neo4j.gds.api.Graph graph,
                                                                                  BfsConsumer perNodeAction,
                                                                                  BfsWithPredecessorConsumer perNeighborAction)

predecessorProcessing

public static MultiSourceBFSAccessMethods predecessorProcessing(org.neo4j.gds.api.Graph graph,
                                                                BfsConsumer perNodeAction,
                                                                BfsWithPredecessorConsumer perNeighborAction,
                                                                long[] sourceNodes)

run

public void run(int concurrency,
                java.util.concurrent.ExecutorService executor)

Runs MS-BFS, possibly in parallel.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object