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https://issues.apache.org/jira/browse/KYLIN-3656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687718#comment-16687718
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ASF GitHub Bot commented on KYLIN-3656:
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hit-lacus opened a new pull request #345: KYLIN-3656 Improve HLLCounter
performance
URL: https://github.com/apache/kylin/pull/345
The current HLLCounter implementation has some room to improve performance,
as we find in our product environment. Improvement related to getCountEstimate
of HLLCounter and constructor of HLLCounter.
- Create HLLCounter from another HLLCounter, we can copy register(using
System.arraycopy) instead of merge. (Constructor of HLLCounter)
- Precompute harmonic mean in the HLLCSnapshot to avoid doing this on the
fly. (getCountEstimate of HLLCounter)
UnitTest has add cost duration compare.
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> Improve HLLCounter performance
> ------------------------------
>
> Key: KYLIN-3656
> URL: https://issues.apache.org/jira/browse/KYLIN-3656
> Project: Kylin
> Issue Type: Improvement
> Affects Versions: all
> Reporter: Chang chen
> Assignee: Chang chen
> Priority: Major
> Fix For: v2.6.0
>
> Attachments: 0001-KYLIN-3656-Improve-HLLCounter-performance.patch,
> image-2018-11-05-18-15-36-463.png
>
>
> The current HLLCounter implementation has some room to improve performance,
> as we find in our product environment.
> # Create HLLCounter from another HLLCounter, we can copy register instead
> of merge
> # To compute harmonic mean in the HLLCSnapshot, we could
> ## using table to cache all 1/2^r without computing on the fly
> ## remove floating addition by using integer addition in the bigger loop
> ## remove branch, e.g. needn't checking whether registers[i] is zero or not,
> although this is minor improvement.
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