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MapReduce >> mail # user >> Re: Input Split vs Task vs attempt vs computation

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Re: Input Split vs Task vs attempt vs computation
I have a few questions i am trying to understand:

1. Is each input split same as a record, (a rec can be a single line or multiple lines).

2. Is each Task a collection of few computations or attempts.

For ex: if i have a small file with 5 lines.

By default there will be 1 line on which each map computation is performed.
So totally 5 computations r done on 1 node.

This means JT will spawn 1 JVM for 1 Tasktracker on a node
and another JVM for map task which will instantiate 5 map objects 1 for each line.

The MT JVM is called the task which will have 5 attempts for  each line.
This means attempt is same as computation.

Please let me know if anything is incorrect.