https://github.com/igrigorik/pregel

Single-node implementation of Google's Pregel framework for graph processing.
https://github.com/igrigorik/pregel

Last synced: about 2 months ago
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Single-node implementation of Google's Pregel framework for graph processing.

• Host: GitHub
• URL: https://github.com/igrigorik/pregel
• Owner: igrigorik
• Created: 2010-10-30T23:12:39.000Z (about 14 years ago)
• Default Branch: master
• Last Pushed: 2012-02-10T17:09:01.000Z (almost 13 years ago)
• Last Synced: 2024-10-31T13:46:44.361Z (2 months ago)
• Language: Ruby
• Homepage:
• Size: 104 KB
• Stars: 74
• Watchers: 6
• Forks: 12
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Pregel

Single-node implementation of Google's Pregel framework for graph processing. It does not provide any of the distributed components, but implements the core functional pieces within a single Ruby VM such that you can develop and run iterative graph algorithms as if you had the full power of Pregel at your disposal.

To learn more about Pregel see following resources:

 * [Pregel, a system for large-scale graph processing](http://portal.acm.org/citation.cfm?id=1582716.1582723)

 * [Large-scale graph computing at Google](http://googleresearch.blogspot.com/2009/06/large-scale-graph-computing-at-google.html)

 * [Phoebus](http://github.com/xslogic/phoebus) is a distributed Erlang implementation of Pregel

# PageRank example with Pregel

To run a PageRank computation on an arbitrary graph, you simply specify the vertices & edges, and then define a compute function for each vertex. The coordinator then partitions the work between a specified number of workers (Ruby threads, in our case), and iteratively executes "supersteps" until we converge on a result. At each superstep, the vertex can read and process incoming messages and then send messages to other vertices. Hence, the full PageRank implementation is:

```ruby

class PageRankVertex < Vertex

  def compute

    if superstep >= 1

      sum = messages.inject(0) {|total,msg| total += msg; total }

      @value = (0.15 / num_nodes) + 0.85 * sum

    end

    if superstep < 30

      deliver_to_all_neighbors(@value / neighbors.size)

    else

      halt

    end

  end

end

```

The above algorithm will run for 30 iterations, at which point all vertices will mark themselves as inactive and the coordinator will terminate our computation.

 * [Computing PageRank for a simple circular graph](https://github.com/igrigorik/pregel/blob/master/spec/coordinator_spec.rb#L52)

 * [Computing PageRank for a more complex grap](https://github.com/igrigorik/pregel/blob/master/spec/coordinator_spec.rb#L70)

# License

(The MIT License)

Copyright (c) 2010 Ilya Grigorik

Permission is hereby granted, free of charge, to any person obtaining

a copy of this software and associated documentation files (the

'Software'), to deal in the Software without restriction, including

without limitation the rights to use, copy, modify, merge, publish,

distribute, sublicense, and/or sell copies of the Software, and to

permit persons to whom the Software is furnished to do so, subject to

the following conditions:

The above copyright notice and this permission notice shall be

included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,

EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY

CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,

TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE

SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.