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From Apache Wiki <wikidi...@apache.org>
Subject [Hama Wiki] Update of "Hamburg" by udanax
Date Wed, 01 Jul 2009 03:02:16 GMT
Dear Wiki user,

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The following page has been changed by udanax:
http://wiki.apache.org/hama/Hamburg

New page:
== Motivation ==
The MapReduce (M/R) programming model is inappropriate to problems based on data where each
portion depends on many other potions and their relations are very complicated. It is because
these problems cause as follows:
 * limit to assigning one reducer
  * In case that the relations of data are very complex, assigning intermediate data to appropriate
reducers by considering their dependency of partitioned graphs may be very hard. Assigning
only one reducer is a straightway to solve complexity dependency, but it is apparent to cause
deterioration of scalability.
 * many M/R iterations
 * or make an M/R program more complicated
  * To avoid above two inefficient methods, the M/R program will be complicated with code
to communicate data among data nodes.

These problems are very common in many areas; especially, many graph problems are exemplary.
Let's write description of an example
Therefore, we try to propose a new programming model, named Hamburg. The main objective of
Hamburg is to support well the problems based on data having complexity dependency one another.
This page is an initial work of our proposal.
== Goal ==
Follow scalability concept of shared-nothing architecture
Support to computation for data having complexity relations, like graph data.

== Hamburg ==
Hambrug is an alternative to M/R programming model. It is based on bulk synchronization parallel
(BSP) model. Like M/R, Hambrug takes advantages from shared-nothing architecture (SN), so
I expect that it will also show scalablity without almost degradation of performance as the
number of participant nodes increases.
A Hamburg based on BSP computation step consists of three sub steps:
 * Computation on data that reside in local storage; it is similar to map operation in M/R.
 * Each node communicates its necessary data into one another.
 * All processors synchronize which waits for all of the communications actions to complete.
The main difference between Hamburg and M/R is that Hamburg does not make intermediate data
aggregate into reducer. Instead, each computation node communicates only necessary data into
one another. 
It will be efficient if total communicated data is smaller then intermediate data to be aggregated
into reducers.

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