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From "Milind Bhandarkar (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3221) Need a "LineBasedTextInputFormat"
Date Wed, 09 Apr 2008 21:38:04 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12587354#action_12587354
] 

Milind Bhandarkar commented on HADOOP-3221:
-------------------------------------------

Arkady,

OneLineInputFormat is not checked into Hadoop yet. I created this jira, so that we can make
the necessary modifications (e.g. LocationHints, adjusting to numMappers etc), and contribute
it.


> Need a "LineBasedTextInputFormat"
> ---------------------------------
>
>                 Key: HADOOP-3221
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3221
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>    Affects Versions: 0.16.2
>         Environment: All
>            Reporter: Milind Bhandarkar
>
> In many "pleasantly" parallel applications, each process/mapper processes the same input
file (s), but with computations are controlled by different parameters.
> (Referred to as "parameter sweeps").
> One way to achieve this, is to specify a set of parameters (one set per line) as input
in a control file (which is the input path to the map-reduce application, where as the input
dataset is specified via a config variable in JobConf.).
> It would be great to have an InputFormat, that splits the input file such that by default,
one line is fed as a value to one map task, and key could be line number. i.e. (k,v) is (LongWritable,
Text).
> If user specifies the number of maps explicitly, each mapper should get a contiguous
chunk of lines (so as to load balance between the mappers.)
> The location hints for the splits should not be derived from the input file, but rather,
should span the whole mapred cluster.
> (Is there a way to do this without having to return an array of nSplits*nTaskTrackers
?)
> Increasing the replication of the "real" input dataset (since it will be fetched by all
the nodes) is orthogonal, and one can use DistributedCache for that.
> (P.S. Please chose a better name for this InputFormat. I am not in love with  "LineBasedText"
name.)

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