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From "Gianmarco De Francisci Morales (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (S4-30) DefaultHasher hashes keys to negative number
Date Sat, 24 Dec 2011 09:56:30 GMT

    [ https://issues.apache.org/jira/browse/S4-30?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175704#comment-13175704
] 

Gianmarco De Francisci Morales commented on S4-30:
--------------------------------------------------

I think that this snippet should do the trick (anyway you lose 1 bit of information because
Java does not have unsigned types and you actually don't care about doing exact arithmetic).
It should be faster than Math.abs() (but I haven't run microbenchmarks on it).

{code}
return (int) (rv & 0x7fffffff);
{code}
                
> DefaultHasher hashes keys to negative number
> --------------------------------------------
>
>                 Key: S4-30
>                 URL: https://issues.apache.org/jira/browse/S4-30
>             Project: Apache S4
>          Issue Type: Bug
>    Affects Versions: 0.4
>         Environment: All - Windows and Linux
>            Reporter: Quoc Nguyen
>            Priority: Blocker
>
> DefaultHasher uses HashAlgorithm hashAlgorithm = HashAlgorithm.FNV1_64_HASH; which hashes
key strings such as 118+18233, 118+17360, 118+17258, 118+18147 and 118+18121 and many more
to negative values which the DefaultPartitioner (int partitionId = (int) (hasher.hash(stringValue)
% partitionCount);) tries to partition the key to incorrect partition.
> Workaround:
> None - stream has those keys, they will get dropped because the partitioner cannot correctly
partition.

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