Response from Brent Douglas:
Hi Vladimir,
I'm not sure this is the same thing being discussed however if it is not
I had intended to request this anyhow. When I looked into using
infinispans's map reduce facility this is the the task I came up with:
http://pastebin.com/7GGjVnVt
I would prefer to specify it as:
http://pastebin.com/HTSq3g66
I'm pretty sure this is the not intended use case but it distributes the
creation of my reports which is what I want. It's not really a big deal
for me as I can get around this limitation by creating a wrapper class
such as in the first example but it would be nice if I did not have
to. Is this a reasonable request?
Also, and this is probably just wrong, when I use this I bundle up the
task and execute it via JMS. Would it be reasonable to make Collator
extend Serializable?
Brent
On 12-01-30 11:47 AM, Vladimir Blagojevic wrote:
Guys,
I was looking at this again recently and I still do not understand how
combiner could have different interface than Reducer! Hadoop forces a
user to implement combiner as a Reducer
http://developer.yahoo.com/hadoop/tutorial/module4.html#functionality
and
http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/Job.html#setCombinerClass%28java.lang.Class%29
In addition, the original paper does not mention any change of types.
What we have admittedly done wrong is to apply Reducer on individual
Mapper without checking if a reduce function is both /commutative/ and
/associative/! This can lead to problems:
http://philippeadjiman.com/blog/2010/01/14/hadoop-tutorial-series-issue-4-to-use-or-not-to-use-a-combiner/
So yes, I am all for adding Combiner (it should do the optional
reducer per mapper we do automatically now) but I do not see why we
have to change the interface!
Regards,
Vladimir
_______________________________________________
infinispan-dev mailing list
infinispan-dev@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/infinispan-dev
_______________________________________________
infinispan-dev mailing list
infinispan-dev@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/infinispan-dev
