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https://issues.apache.org/jira/browse/LUCENE-1604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12698873#action_12698873
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Michael McCandless commented on LUCENE-1604:
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bq. If guys at Java HotSpot Compiler are doing their homework, checking
something != null before accessing something should come almost for free,
because each access checks for null anyway.
The problem is, depending on the result of the null check, we do very different
things; I think we are relying on the CPU to correctly predict the branch,
which I even wonder about since multiple threads could be running that code
with the if going different ways. And even a correct prediction there's still
[small] added cost...
> Stop creating huge arrays to represent the absense of field norms
> -----------------------------------------------------------------
>
> Key: LUCENE-1604
> URL: https://issues.apache.org/jira/browse/LUCENE-1604
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.9
> Reporter: Shon Vella
> Priority: Minor
> Fix For: 2.9
>
> Attachments: LUCENE-1604.patch
>
>
> Creating and keeping around huge arrays that hold a constant value is very
> inefficient both from a heap usage standpoint and from a localility of
> reference standpoint. It would be much more efficient to use null to
> represent a missing norms table.
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