Calculation and Turing-Completeness

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FIrst off- it's nice. I come from the Unix tradition of short&sweet. Of course, 
I want a new feature :)

Hadoop workflow drivers all seem to believe in code&fire&forget: some allow 
if/then/else branching and oozie supports expressions. I have not found any 
that support conditionally starting over or jumping into the middle.

Many machine learning algorithms use repetitive calculations driving towards a 
finishing condition (often a maximum error value). The Mahout project, which 
focuses on machine learning on Map/Reduce, has a great many multistage 
calculation jobs which have to be coded in Java entirely due to this.

Here is a very simple feature addition that would solve all of these: a 
decision node that calls a Java object. One of the possible decisions would be: 
branch X is a goto to another place in the workflow. This would hack the 
generation numbers on the paths after the target node.

Original issue reported on code.google.com by lance.no...@gmail.com on 31 Jul 2011 at 11:27