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Posted to dev@hbase.apache.org by "stack (JIRA)" <ji...@apache.org> on 2009/01/20 00:52:59 UTC
[jira] Reopened: (HBASE-1136) HashFunction inadvertently destroys
some randomness
[ https://issues.apache.org/jira/browse/HBASE-1136?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
stack reopened HBASE-1136:
--------------------------
Reopening. TestFilter fails. Reverted patch. Can you fix Jonathan?
> HashFunction inadvertently destroys some randomness
> ---------------------------------------------------
>
> Key: HBASE-1136
> URL: https://issues.apache.org/jira/browse/HBASE-1136
> Project: Hadoop HBase
> Issue Type: Bug
> Reporter: Jonathan Ellis
> Fix For: 0.20.0
>
> Attachments: hash.patch
>
>
> the code
> for (int i = 0, initval = 0; i < nbHash; i++) {
> initval = result[i] = Math.abs(hashFunction.hash(b, initval) % maxValue);
> }
> restricts initval for the next hash to the [0, maxValue) range of the hash indexes returned. This is suboptimal, particularly for larger nbHash and smaller maxValue. Instead, use:
> for (int i = 0, initval = 0; i < nbHash; i++) {
> initval = hashFunction.hash(b, initval);
> result[i] = Math.abs(initval) % maxValue;
> }
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