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From Thomas Jungblut <thomas.jungb...@googlemail.com>
Subject Re: About the memory requirements of Hama/Pregel
Date Wed, 29 Jun 2011 06:15:05 GMT
Hi Claudio,

we don't have an IO System to keep the data, so you're forced to manage this
by yourself. Never the less the example will load your input into a HashMap
for performance. So you're right that you're graph has to fit at least into
But at least you can fork your own PageRank example and add disk paging to

Have fun.

2011/6/28 Claudio Martella <claudio.martella@tis.bz.it>

> Hi,
> I was considering an issue not discussed in Pregel paper. One
> interesting thing about MapReduce is that the memory limit for each job
> in a cluster node is the number of task assigned to that node * the
> memory allocated by each task (plus of course the framework overhead).
> The input data is iteratively loaded (and kind of emitted too) from
> storage and doesn't need to be kept in memory or loaded together in
> advance.
> In Pregel, to me, it looks like the whole graph has to fit in memory
> among the cluster nodes. As it is somehow stateful and doesn't have an
> iterative job-job nature as MapReduce, at the beginning of the job all
> the vertices and their data have to be loaded into the cluster (and kept
> in memory).
> So the question is: if i want to run Pagerank over my graph, do I need
> to be able to store the whole graph in memory?
> Thanks!
> --
> Claudio Martella
> Digital Technologies
> Unit Research & Development - Analyst
> TIS innovation park
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Thomas Jungblut

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