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Removed option to find path with exact depth from ShortestPath
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It does not make sense to find a shortest path with specified length and ExactDepthPathFinder already provides that functionality.
 - Added further testing for ExactDepthPathFinder.
 - GraphAlgoFactory now uses ExactDepthPathFinder instead of ShortsetPath.
 - Fixed ExactDepthPathFinder not handeling neighbouring node (depth 1).

Fixing imports
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@burqen
burqen committed May 19, 2015
1 parent 3132c99 commit 6884c91
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Showing 8 changed files with 350 additions and 224 deletions.
95 changes: 48 additions & 47 deletions community/graph-algo/src/main/java/org/neo4j/graphalgo/GraphAlgoFactory.java
View file
Expand Up @@ -23,6 +23,7 @@
import org.neo4j.graphalgo.impl.path.AllPaths;
import org.neo4j.graphalgo.impl.path.AllSimplePaths;
import org.neo4j.graphalgo.impl.path.Dijkstra;
import org.neo4j.graphalgo.impl.path.ExactDepthPathFinder;
import org.neo4j.graphalgo.impl.path.ShortestPath;
import org.neo4j.graphalgo.impl.util.DoubleEvaluator;
import org.neo4j.graphdb.Node;
Expand All @@ -37,7 +38,7 @@
* Static factory methods for the recommended implementations of common
* graph algorithms for Neo4j. The algorithms exposed here are implementations
* which are tested extensively and also scale on bigger graphs.
*
*
* @author Mattias Persson
*/
public abstract class GraphAlgoFactory
Expand Down Expand Up @@ -73,7 +74,7 @@ public static PathFinder<Path> allPaths( PathExpander expander, int maxDepth )
{
return new AllPaths( maxDepth, expander );
}

/**
* Returns an algorithm which can find all simple paths between two
* nodes. These returned paths cannot contain loops (i.e. a node cannot
Expand Down Expand Up @@ -107,7 +108,7 @@ public static PathFinder<Path> allSimplePaths( PathExpander expander,
{
return new AllSimplePaths( maxDepth, expander );
}

/**
* Returns an algorithm which can find all shortest paths (that is paths
* with as short {@link Path#length()} as possible) between two nodes. These
Expand All @@ -130,7 +131,7 @@ public static PathFinder<Path> shortestPath( RelationshipExpander expander, int
* with as short {@link Path#length()} as possible) between two nodes. These
* returned paths cannot contain loops (i.e. a node cannot occur more than
* once in any returned path).
*
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param maxDepth the max {@link Path#length()} returned paths are allowed
Expand All @@ -141,13 +142,13 @@ public static PathFinder<Path> shortestPath( PathExpander expander, int maxDepth
{
return new ShortestPath( maxDepth, expander );
}

/**
* Returns an algorithm which can find all shortest paths (that is paths
* with as short {@link Path#length()} as possible) between two nodes. These
* returned paths cannot contain loops (i.e. a node cannot occur more than
* once in any returned path).
*
*
* @param expander the {@link RelationshipExpander} to use for expanding
* {@link Relationship}s for each {@link Node}.
* @param maxDepth the max {@link Path#length()} returned paths are allowed
Expand All @@ -160,13 +161,13 @@ public static PathFinder<Path> shortestPath( RelationshipExpander expander, int
{
return new ShortestPath( maxDepth, expander, maxHitCount );
}

/**
* Returns an algorithm which can find all shortest paths (that is paths
* with as short {@link Path#length()} as possible) between two nodes. These
* returned paths cannot contain loops (i.e. a node cannot occur more than
* once in any returned path).
*
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param maxDepth the max {@link Path#length()} returned paths are allowed
Expand All @@ -179,12 +180,12 @@ public static PathFinder<Path> shortestPath( PathExpander expander, int maxDepth
{
return new ShortestPath( maxDepth, expander, maxHitCount );
}

/**
* Returns an algorithm which can find simple all paths of a certain length
* between two nodes. These returned paths cannot contain loops (i.e. a node
* could not occur more than once in any returned path).
*
*
* @param expander the {@link RelationshipExpander} to use for expanding
* {@link Relationship}s for each {@link Node}.
* @param length the {@link Path#length()} returned paths will have, if any
Expand All @@ -193,14 +194,14 @@ public static PathFinder<Path> shortestPath( PathExpander expander, int maxDepth
*/
public static PathFinder<Path> pathsWithLength( RelationshipExpander expander, int length )
{
return new ShortestPath( length, expander, Integer.MAX_VALUE, true );
return new ExactDepthPathFinder( expander, length, Integer.MAX_VALUE, false );
}

/**
* Returns an algorithm which can find simple all paths of a certain length
* between two nodes. These returned paths cannot contain loops (i.e. a node
* could not occur more than once in any returned path).
*
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Node}.
* @param length the {@link Path#length()} returned paths will have, if any
Expand All @@ -209,20 +210,20 @@ public static PathFinder<Path> pathsWithLength( RelationshipExpander expander, i
*/
public static PathFinder<Path> pathsWithLength( PathExpander expander, int length )
{
return new ShortestPath( length, expander, Integer.MAX_VALUE, true );
return new ExactDepthPathFinder( expander, length, Integer.MAX_VALUE, false );
}

/**
* Returns a {@link PathFinder} which uses the A* algorithm to find the
* cheapest path between two nodes. The definition of "cheap" is the lowest
* possible cost to get from the start node to the end node, where the cost
* is returned from {@code lengthEvaluator} and {@code estimateEvaluator}.
* These returned paths cannot contain loops (i.e. a node cannot occur more
* than once in any returned path).
*
*
* See http://en.wikipedia.org/wiki/A*_search_algorithm for more
* information.
*
*
* @param expander the {@link RelationshipExpander} to use for expanding
* {@link Relationship}s for each {@link Node}.
* @param lengthEvaluator evaluator that can return the cost represented
Expand All @@ -246,10 +247,10 @@ public static PathFinder<WeightedPath> aStar( RelationshipExpander expander,
* is returned from {@code lengthEvaluator} and {@code estimateEvaluator}.
* These returned paths cannot contain loops (i.e. a node cannot occur more
* than once in any returned path).
*
*
* See http://en.wikipedia.org/wiki/A*_search_algorithm for more
* information.
*
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param lengthEvaluator evaluator that can return the cost represented
Expand All @@ -265,18 +266,18 @@ public static PathFinder<WeightedPath> aStar( PathExpander expander,
{
return new AStar( expander, lengthEvaluator, estimateEvaluator );
}

/**
* Returns a {@link PathFinder} which uses the Dijkstra algorithm to find
* the cheapest path between two nodes. The definition of "cheap" is the
* lowest possible cost to get from the start node to the end node, where
* the cost is returned from {@code costEvaluator}. These returned paths
* cannot contain loops (i.e. a node cannot occur more than once in any
* returned path).
*
*
* See http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm for more
* information.
*
*
* @param expander the {@link RelationshipExpander} to use for expanding
* {@link Relationship}s for each {@link Node}.
* @param costEvaluator evaluator that can return the cost represented
Expand All @@ -289,18 +290,18 @@ public static PathFinder<WeightedPath> dijkstra( RelationshipExpander expander,
{
return new Dijkstra( expander, costEvaluator );
}

/**
* Returns a {@link PathFinder} which uses the Dijkstra algorithm to find
* the cheapest path between two nodes. The definition of "cheap" is the
* lowest possible cost to get from the start node to the end node, where
* the cost is returned from {@code costEvaluator}. These returned paths
* cannot contain loops (i.e. a node cannot occur more than once in any
* returned path).
*
*
* See http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm for more
* information.
*
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param costEvaluator evaluator that can return the cost represented
Expand All @@ -313,13 +314,13 @@ public static PathFinder<WeightedPath> dijkstra( PathExpander expander,
{
return new Dijkstra( expander, costEvaluator );
}

/**
* See {@link #dijkstra(RelationshipExpander, CostEvaluator)}.
*
*
* Uses a cost evaluator which uses the supplied property key to
* represent the cost (values of type <bold>double</bold>).
*
* represent the cost (values of type <bold>double</bold>).
*
* @param expander the {@link RelationshipExpander} to use for expanding
* {@link Relationship}s for each {@link Node}.
* @param relationshipPropertyRepresentingCost the property to represent cost
Expand All @@ -332,13 +333,13 @@ public static PathFinder<WeightedPath> dijkstra( RelationshipExpander expander,
{
return dijkstra( expander, new DoubleEvaluator( relationshipPropertyRepresentingCost ) );
}

/**
* See {@link #dijkstra(RelationshipExpander, CostEvaluator)}.
*
*
* Uses a cost evaluator which uses the supplied property key to
* represent the cost (values of type <bold>double</bold>).
*
* represent the cost (values of type <bold>double</bold>).
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param relationshipPropertyRepresentingCost the property to represent cost
Expand All @@ -351,13 +352,13 @@ public static PathFinder<WeightedPath> dijkstra( PathExpander expander,
{
return dijkstra( expander, new DoubleEvaluator( relationshipPropertyRepresentingCost ) );
}

/**
* See {@link #dijkstra(RelationshipExpander, CostEvaluator)}.
*
*
* Uses a cost evaluator which uses the supplied property key to
* represent the cost (values of type <bold>double</bold>).
*
* represent the cost (values of type <bold>double</bold>).
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param stateFactory initial state for the traversal branches.
Expand All @@ -373,10 +374,10 @@ public static PathFinder<WeightedPath> dijkstra( PathExpander expander,

/**
* See {@link #dijkstra(RelationshipExpander, CostEvaluator)}.
*
*
* Uses a cost evaluator which uses the supplied property key to
* represent the cost (values of type <bold>double</bold>).
*
* represent the cost (values of type <bold>double</bold>).
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param stateFactory initial state for the traversal branches.
Expand All @@ -389,13 +390,13 @@ public static PathFinder<WeightedPath> dijkstra( PathExpander expander,
{
return new Dijkstra( expander, stateFactory, costEvaluator );
}

/**
* See {@link #dijkstra(RelationshipExpander, CostEvaluator)}.
*
*
* Uses a cost evaluator which uses the supplied property key to
* represent the cost (values of type <bold>double</bold>).
*
* represent the cost (values of type <bold>double</bold>).
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param stateFactory initial state for the traversal branches.
Expand All @@ -412,10 +413,10 @@ public static PathFinder<WeightedPath> dijkstra( PathExpander expander,

/**
* See {@link #dijkstra(RelationshipExpander, CostEvaluator)}.
*
*
* Uses a cost evaluator which uses the supplied property key to
* represent the cost (values of type <bold>double</bold>).
*
* represent the cost (values of type <bold>double</bold>).
*
* @param expander the {@link PathExpander} to use for expanding
* {@link Relationship}s for each {@link Path}.
* @param stateFactory initial state for the traversal branches.
Expand Down
41 changes: 20 additions & 21 deletions community/graph-algo/src/main/java/org/neo4j/graphalgo/impl/path/ExactDepthPathFinder.java
View file
Expand Up @@ -19,13 +19,6 @@
*/
package org.neo4j.graphalgo.impl.path;

import static org.neo4j.graphdb.traversal.Evaluators.atDepth;
import static org.neo4j.graphdb.traversal.Evaluators.toDepth;
import static org.neo4j.kernel.StandardExpander.toPathExpander;
import static org.neo4j.kernel.Traversal.bidirectionalTraversal;
import static org.neo4j.kernel.Traversal.traversal;
import static org.neo4j.kernel.Uniqueness.RELATIONSHIP_GLOBAL;

import org.neo4j.graphalgo.impl.util.LiteDepthFirstSelector;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.PathExpander;
Expand All @@ -35,6 +28,13 @@
import org.neo4j.graphdb.traversal.TraversalBranch;
import org.neo4j.graphdb.traversal.TraversalDescription;
import org.neo4j.graphdb.traversal.Traverser;
import org.neo4j.graphdb.traversal.Uniqueness;

import static org.neo4j.graphdb.traversal.Evaluators.atDepth;
import static org.neo4j.graphdb.traversal.Evaluators.toDepth;
import static org.neo4j.kernel.StandardExpander.toPathExpander;
import static org.neo4j.kernel.Traversal.bidirectionalTraversal;
import static org.neo4j.kernel.Traversal.traversal;

/**
* Tries to find paths in a graph from a start node to an end node where the
Expand All @@ -53,39 +53,38 @@ public class ExactDepthPathFinder extends TraversalPathFinder
private final PathExpander expander;
private final int onDepth;
private final int startThreshold;
private final Uniqueness uniqueness;

public ExactDepthPathFinder( RelationshipExpander expander, int onDepth,
int startThreshold )
public ExactDepthPathFinder( RelationshipExpander expander, int onDepth, int startThreshold, boolean allowLoops )
{
this( toPathExpander( expander ), onDepth, startThreshold );
this( toPathExpander( expander ), onDepth, startThreshold, allowLoops );
}

public ExactDepthPathFinder( PathExpander expander, int onDepth, int startThreshold )
public ExactDepthPathFinder( PathExpander expander, int onDepth, int startThreshold, boolean allowLoops )
{
this.expander = expander;
this.onDepth = onDepth;
this.startThreshold = startThreshold;
this.uniqueness = allowLoops ? Uniqueness.RELATIONSHIP_GLOBAL : Uniqueness.NODE_PATH;
}

@Override
protected Traverser instantiateTraverser( Node start, Node end )
{
TraversalDescription side = traversal().breadthFirst().expand( expander ).uniqueness( RELATIONSHIP_GLOBAL ).order(
new BranchOrderingPolicy()
TraversalDescription side =
traversal().breadthFirst().uniqueness( uniqueness ).order( new BranchOrderingPolicy()
{
@Override
public BranchSelector create( TraversalBranch startSource, PathExpander expander )
{
return new LiteDepthFirstSelector( startSource,
startThreshold, expander );
return new LiteDepthFirstSelector( startSource, startThreshold, expander );
}
} );

return bidirectionalTraversal()
.startSide( side.evaluator( toDepth( onDepth/2 ) ) )
.endSide( side.evaluator( toDepth( onDepth-onDepth/2 ) ) )
return bidirectionalTraversal().startSide( side.expand( expander ).evaluator( toDepth( onDepth / 2 ) ) )
.endSide( side.expand( expander.reverse() ).evaluator( toDepth( onDepth - onDepth / 2 ) ) )
.collisionEvaluator( atDepth( onDepth ) )
// TODO Level side selector will make the traversal return wrong result, why?
// .sideSelector( SideSelectorPolicies.LEVEL, onDepth )
// TODO Level side selector will make the traversal return wrong result, why?
// .sideSelector( SideSelectorPolicies.LEVEL, onDepth )
.traverse( start, end );
}
}

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