[Haskell-cafe] Why monoids will abide...

Eugene Kirpichov ekirpichov at gmail.com
Thu Jan 22 10:44:04 EST 2009

Thanks; I saw you mention the paper before, but now I finally started
reading it :)
By the way, the paper *does* arrange an extra infrastructure for
mappending only adjacent results.
Looks like with a commutative monoid, a fold could be done in a fully
distributed fashion, however it would no more be a scan.

2009/1/22 Dan Piponi <dpiponi at gmail.com>:
> On Wed, Jan 21, 2009 at 11:12 PM, Eugene Kirpichov <ekirpichov at gmail.com> wrote:
>> To my mind, in the map-reduce case you generally need a commutative
>> monoid. Or, you need an extra infrastructure that mappend's only
>> results from adjacent machines, or something like that.
> This is a good paper on the stuff I'm talking about:
> http://citeseer.ist.psu.edu/blelloch90prefix.html It doesn't
> explicitly mention monoids but it's all about associative operations
> with identity.
> --
> Dan

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