On Wed, Jun 20, 2012 at 6:19 AM, Sebastian Schelter <[email protected]> wrote:
> I'm just asking because I review a paper where Mahout's SVM support on > M/R is mentioned :) > Interesting. We don't have anything release, I don't think. > As far as I recall All-Reduce is map + an aggregation tree that feeds > back the result? > Yes. Exactly, except that there isn't a map step. It typically also requires the use of combiners so that it can use a tree to broadcast to the aggregating node. This allows O(n / log n) average parallelism during aggregation and is critical for performance. > Giraph supports aggregators where every worker instance preaggregates > the data, the master computes the final aggregation and feeds it back to > the workers. So you could have a 1-level aggregation tree out of the box. > That won't cut it in the end, but might be useful in the short term since it avoids the horrible map-reduce iteration cost. The goal is to sum a (big) vector from each node. A 1-level aggregation tree requires that all the vectors be copied to a single node where the sums will be done. > Best, > Sebastian > > On 20.06.2012 15:07, Ted Dunning wrote: > > No. > > > > But L1 regularization for hinge loss should give essentially identical > results. We currently support logit loss but this is pluggable. This is in > the sgd framework which currently lacks a map reduce implementation. > > > > Speaking of that, does anybody offhand know whether giraph supports an > allreduce primitive. That is the primary thing missing to get parallel sgd. > > > > Sent from my iPhone > > > > On Jun 20, 2012, at 6:01 AM, Sebastian Schelter <[email protected]> wrote: > > > >> Hi, > >> > >> Did we ever have a M/R implementation of an SVM? > >> > >> Best, > >> Sebastian > >
