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Posted to mapreduce-dev@hadoop.apache.org by "Anubhav Dhoot (JIRA)" <ji...@apache.org> on 2014/07/18 01:10:05 UTC

[jira] [Created] (MAPREDUCE-5979) MR1 FairScheduler zero weight can cause sort failures

Anubhav Dhoot created MAPREDUCE-5979:
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             Summary: MR1 FairScheduler zero weight can cause sort failures
                 Key: MAPREDUCE-5979
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5979
             Project: Hadoop Map/Reduce
          Issue Type: Bug
          Components: scheduler
    Affects Versions: 1.2.1
            Reporter: Anubhav Dhoot


When the weight is set to zero (which is possible with a custom weight adjuster) we can get failures in comparing schedulables.
This is because when calculating running tasks to weight ratio could result in a 0.0/0.0 which ends up as NaN. Comparisons with NaN are undefined such that (int)Math.signum(NaN - anyNumber) will be 0 causing different criteria to be used in comparison which may not be consistent. This will result in 
{{IllegalArgumentException: Comparison method violates its general contract!}}
 



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