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From Venkata Sastry Malladi <>
Subject All pairs shortest paths
Date Mon, 24 Sep 2012 18:24:24 GMT
I'm thinking of modifying the simple shortest paths algorithm so that it
calculates the shortest paths between all pairs of nodes (not just from a
single source node). I wanted to get some general advice on whether these
are feasible in Giraph:

1. Without quitting the job after all vertices voteToHalt(), is it possible
to just restart from superstep 0, but with a different source node? In
other words, when we want to do simultaneous runs of the simple shortest
paths algorithm, how can we avoid the overhead of re-reading the graph into
memory between the runs?

2. Is it possible to run some kind of reducer before the vertices are
written to the output? Let's say the VertexWriter outputs something like
(Source, Destination) -> Route for each node. Is it possible to combine
many such outputs to produce a single output? Like (Source, Destination) -
> (Route1, Route2, Route3).


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