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From Felix Halim <felix.ha...@gmail.com>
Subject Re: Pregel article
Date Fri, 02 Jul 2010 12:04:40 GMT
Exactly how to activate a particular vertex is not clear from the
paper (is it random access?) and this feature is probably not as good
as it sounds for complex graph algorithms. It might be better off to
assume all vertices are active (to reduce the overhead of the flag
needed and the space to make it randomly accessible, by storing it in
blocks or whatever).

Here is my argument:

The way Pregel (and existing MR) works is iterative, where each
iteration is separated by a super-step barrier where all messages have
to arrive. Algorithms that have fewer super-steps are preferable than
those that have large number of super-steps. In fact, we should
measure Algorithms in terms of the number of super-steps required. To
minimize the number of super-steps, likely we need to activate as much
vertices as possible to do all the work in current super-step, rather
than spill-over to the next super-step. In this case, the feature to
"turn off" vertices is useless, since most of the time all vertices
will be active to effectively reduce the number of super-steps.

Unfortunately, I don't have experiments to backup my argument... I
don't have Pregel...

Felix Halim

On Fri, Jul 2, 2010 at 7:37 PM, Claudio Martella
<claudio.martella@tis.bz.it> wrote:
> I did too. See:
> http://blog.acaro.org/entry/pregel-is-out-but-what-is-pregel
> Felix Halim wrote:
>> I have. See my comment in this blog:
>> http://blog.udanax.org/2010/06/summary-of-google-pregel.html
>> Felix Halim
>> On Tue, Jun 8, 2010 at 4:00 AM, Mark Kerzner <markkerzner@gmail.com> wrote:
>>> Hi,
>>> anybody has read it?
>>> Thank you,
>>> Mark
> --
> Claudio Martella
> Digital Technologies
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