[
https://issues.apache.org/jira/browse/HADOOP-3383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12621081#action_12621081
]
Steve Loughran commented on HADOOP-3383:
----------------------------------------
the whole 17/37 stuff comes from effective Java (page 37 :), and some of the
IDEs implement the feature, so its become quite common:
http://www.google.com/codesearch?hl=en&q=+lang:java+%5C*37&start=20&sa=N
Maybe the goal was to have 37 * (17 + f(x)), but the braces were left out. Even
then, I don't know whether is beneficial or just some form of superstition.
> Redundant computation in hashCode() implemenation
> -------------------------------------------------
>
> Key: HADOOP-3383
> URL: https://issues.apache.org/jira/browse/HADOOP-3383
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Reporter: Tsz Wo (Nicholas), SZE
>
> In some hashCode() implementation (e.g. Block.hashCode()), the formula has
> the form
> {noformat}
> 37 * 17 + f(x),
> {noformat}
> where f( x ) is some function. Adding 37*17 to f( x ) shifts the value of f(
> x ). It is not effective to do shifting in hash functions. The computation
> is redundant.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
