Random Walks on Graphs

Implementing RWR on Giraph should be a very simple modification of the SimplePageRankVertex code.

if ( myID == sourceID )
      DoubleWritable vertexValue = new DoubleWritable((0.15f + 0.85f * sum);
else
      DoubleWritable vertexValue = new DoubleWritable(0.85f * sum);

It would be nice to make it as configurable as possible by using parametric damping factors, preference vectors, strongly preferential, etc...
More or less along these lines:
http://law.dsi.unimi.it/software/docs/it/unimi/dsi/law/rank/PageRank.html