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shortestPath with findSinglePath
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Mirko Nasato  
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 More options Apr 29 2012, 5:44 am
From: Mirko Nasato <mirko.nas...@gmail.com>
Date: Sun, 29 Apr 2012 02:44:51 -0700 (PDT)
Local: Sun, Apr 29 2012 5:44 am
Subject: shortestPath with findSinglePath
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Hi all,

Given

  PathFinder<Path> finder = GraphAlgoFactory.shortestPath(expander, 4);
  finder.findSinglePath(startNode, endNode);

seems like findSinglePath is not guaranteed to find the *shortest* path, it
just returns the first path it finds with length <= 4.

So it can return a path of length 4 even though one of length 3 exists -
and can be found using findAllPaths instead. Is that by design?

(I'm using Neo4j 1.7.)

Thanks

Mirko


 
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Mattias Persson  
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 More options Apr 29 2012, 8:34 am
From: Mattias Persson <matt...@neotechnology.com>
Date: Sun, 29 Apr 2012 14:34:51 +0200
Local: Sun, Apr 29 2012 8:34 am
Subject: Re: [Neo4j] shortestPath with findSinglePath
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Have you got an example where it returns a path that isn't the shortest?
findSinglePath will by design return the shortest path. The maxLength (=4
in your case) parameter is just to limit how far it is allowed to go if it
doesn't find any shorter path along the way.

2012/4/29 Mirko Nasato <mirko.nas...@gmail.com>

--
Mattias Persson, [matt...@neotechnology.com]
Hacker, Neo Technology
www.neotechnology.com

 
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Mirko Nasato  
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 More options Apr 29 2012, 9:41 am
From: Mirko Nasato <mirko.nas...@gmail.com>
Date: Sun, 29 Apr 2012 06:41:14 -0700 (PDT)
Local: Sun, Apr 29 2012 9:41 am
Subject: Re: [Neo4j] shortestPath with findSinglePath
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Hi Mattias,

Yes I did encounter an actual example where findSinglePath doesn't seem to
return the shortest path. In fact it returns a path of length 4 with
maxDepth = 4, and of length 3 with maxDepth = 3.

I have a graph of Wikipedia pages and their links. Recreating it is a bit
involved because you need a Wikipedia dump to start with, but my code is on
GitHub <https://github.com/mirkonasato/graphipedia>.

Here's what I see (using Groovy just for its interactive shell)

  groovy:000> println graphipedia.findPath("Microsoft", "Hotels.com",
4).join(" --> ")
  Microsoft --> Windows 7 --> Steven Sinofsky --> Cornell University -->
Hotels.com

  groovy:000> println graphipedia.findPath("Microsoft", "Hotels.com",
3).join(" --> ")
  Microsoft --> Human Rights Campaign --> Cornell University --> Hotels.com

  groovy:000> graphipedia.findShortestPaths("Microsoft", "Hotels.com",
4).each { path -> println path.join(" --> ") }
  Microsoft --> Bill Gates --> Cornell University --> Hotels.com
  Microsoft --> Human Rights Campaign --> Cornell University --> Hotels.com

In GraphipediaService<https://github.com/mirkonasato/graphipedia/blob/master/graphipedia-qu...>findPath calls findSinglePath and findShortestPaths calls findAllPaths.

Thanks

Mirko


 
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Mirko Nasato  
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 More options Apr 30 2012, 7:08 am
From: Mirko Nasato <mirko.nas...@gmail.com>
Date: Mon, 30 Apr 2012 04:08:56 -0700 (PDT)
Local: Mon, Apr 30 2012 7:08 am
Subject: Re: [Neo4j] shortestPath with findSinglePath
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Mattias Persson  
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 More options May 1 2012, 5:13 pm
From: Mattias Persson <matt...@neotechnology.com>
Date: Tue, 1 May 2012 23:13:16 +0200
Local: Tues, May 1 2012 5:13 pm
Subject: Re: [Neo4j] shortestPath with findSinglePath
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Thanks, I'll have a look at it as it seems to me like you've found a bug!

2012/4/30 Mirko Nasato <mirko.nas...@gmail.com>

--
Mattias Persson, [matt...@neotechnology.com]
Hacker, Neo Technology
www.neotechnology.com

 
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