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JobInProgress contains two sets of TaskInProgress instances:

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  TaskInProgress maps\[\], an array holding one tip per split

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  TaskInProgress reduces\[\], an array holding one tip per partition \\

Method initTask() fills out those tips. initTask also creates:

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  hostMaps\[\], which cotains a mapping from a host to file split id's that the host is holding on DFS. \\

JobInProgress also offers two methods for creating a !Task instance to run, out of maps\[\] and reduces\[\]:

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InputFormat is an interface for instantiating file splits and the readers for map task.

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  FileSplit\[\] getSplits(), creates an array of FileSplit for the job. A FileSplit is a span of a given file.

• RecordReader getRecordReader(), creates a reader for a given split.
  

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