[infinispan-dev] [inifnispan-dev] MapReduce enhancement

[Mircea Markus]

On 2 Jan 2012, at 16:49, Vladimir Blagojevic wrote:

> Hi Ondra,
> 
> On 12-01-02 9:40 AM, Ondra Nevelik wrote:
>> Hi all,
>> I was supposed to write an arbitrary app with Infinispan so I wanted to rewrite one of my programs that is implemented using Hadoop MapReduce to have a comparison of performance between the two.
>> 
>> However the way MapReduce is done in Infinispan right now greatly limits the number of problems that can be solved with it - there is a reduce phase on local data on each of the compute nodes to decrease the amount of data transferred. There is a "global" reduce after that. This means that the types of input keys/values has to be the same as output types and that differs from the original MapReduce concept.
> This is simply not true!
Vladimir, I think Ondra refers to the fact that Reduce.reduce function consumes and returns the same type of objects: VOut [1]
IIRC the reason behind this restrictive signature was to allow all sorts of internal optimisations, e.g. parallelising the reduce phase.  

[1] http://bit.ly/vO0GjY