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From "Kaepke, Marc" <marc.kae...@haw-hamburg.de>
Subject Re: Gelly PageRank implementations in 1.2 to 1.3
Date Sun, 23 Jul 2017 10:38:36 GMT
Hi Greg,

I do an evaluation between Gelly and GraphX (Spark). Both frameworks implement PageRank and
Gelly provides a lot of variants (*thumbs up*).
During a really small initial test I get for the vertex-centric, scatter-gather and gsa version
the same ranking result. Just the implementation in 1.3.X (without any graph model) computed
a different result (ranking).


/* vertex centric */
DataSet<Vertex<Double, Double>> pagerankVC = small.run(new PageRank<>(0.5,
10));
System.err.println("VC");
pagerankVC.printToErr();

/* scatter gather */
DataSet<Vertex<Double, Double>> pageRankSG = small
    .run(new org.apache.flink.graph.library.PageRank<>(0.5, 10));
System.err.println("SG");
pageRankSG.printToErr();

/* gsa */
DataSet<Vertex<Double, Double>> pageRankGSA = small.run(new GSAPageRank<>(0.5,
10));
System.err.println("GSA");
pageRankGSA.printToErr();

/* without graph model */
DataSet<Result<Double>> pageRankDI = small
    .run(new PageRank<>(0.5, 10));
System.err.println("delta iteration");
pageRankDI.printToErr();

My input graph is:
vertices

  *   id 1, val 0
  *   id 2, val 0
  *   id 3, val 0
  *   id 4, val 0

edges

  *   src 1, trg 2, val 3
  *   src 1, trg 1, val 2
  *   src 2, trg 1, val 3
  *   src 2, trg 4, val 6

Ranking output

  *   vertex-centric
     *   id 4 with 1.16
     *   id 1 with 1.103
     *   id 2 with 0.815
     *   id 3 with 0
  *   sg and gsa
     *   id 4 with 2.208
     *   id 1 with 2.114
     *   id 2 with 1.546
     *   id 3 with 0
  *   new PageRank in Gelly 1.3.X
     *   id 1 with 0.392
     *   id 2 with 0.313
     *   id 4 with 0.294

Do you know why?


Best
Marc


Am 23.07.2017 um 02:22 schrieb Greg Hogan <code@greghogan.com<mailto:code@greghogan.com>>:

Hi Marc,

PageRank and GSAPageRank were moved to the flink-gelly-examples jar in the org.apache.flink.graph.examples
package. A library algorithm was added that supports both source and sink vertices. This limitation
of the old algorithms was noted in the class documentation and I understand to be an effect
of delta iterations. The new implementation is also significantly faster (https://github.com/apache/flink/pull/2733#issuecomment-278789830).

PageRank can be run using the examples jar from the command line, for example (don’t wildcard
the jar file as in the documentation until we get the javadoc jar removed from the next release).

$ mv opt/flink-gelly* lib/
$ ./bin/flink run examples/gelly/flink-gelly-examples_2.11-1.3.1.jar \
    --algorithm PageRank \
    --input CSV --type integer --simplify directed --input_filename <filename> --input_field_delimiter
$'\t' \
    --output print

The output can also be written to CSV in similar fashion to the input.

The code to call the library PageRank from the examples driver is as with any GraphAlgorithm
(https://github.com/apache/flink/blob/release-1.3/flink-libraries/flink-gelly-examples/src/main/java/org/apache/flink/graph/drivers/PageRank.java):

graph.run(new PageRank<K, VV, EV>(dampingFactor, iterations,  convergenceThreshold));

Please let us know of any issues or additional questions!

Greg


On Jul 22, 2017, at 4:33 PM, Kaepke, Marc <marc.kaepke@haw-hamburg.de<mailto:marc.kaepke@haw-hamburg.de>>
wrote:

Hi there,

why was the PageRank version (which implements the GraphAlgorithm interface) removed in 1.3?

How can I use the new PageRank implementation in 1.3.x?

Why PageRank doesn’t use the graph processing models (vertex-centric, sg or gsa) anymore?

Thanks!

Bests,
marc

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