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https://issues.apache.org/jira/browse/HADOOP-6166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12745143#action_12745143
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Tsz Wo (Nicholas), SZE commented on HADOOP-6166:
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> Because the '8' variants shift to one byte at a time if the input is less
> than 8 bytes, they perform worse than the old PureJavaCrc32 at the 4 byte to
> 7 byte level. Is this important? It would be useful to know how often the crc
> code is called on small byte chunks. We can get this to near PureJavaCrc32
> speeds for 4 byte sizes if we add a four byte at a time block to 8_8d.
I tried this before but it did not help. BTW, the while-loop in the middle
should be an if-statement since we have len <= 7.
> Improve PureJavaCrc32
> ---------------------
>
> Key: HADOOP-6166
> URL: https://issues.apache.org/jira/browse/HADOOP-6166
> Project: Hadoop Common
> Issue Type: Improvement
> Components: util
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Tsz Wo (Nicholas), SZE
> Attachments: c6166_20090722.patch, c6166_20090722_benchmark_32VM.txt,
> c6166_20090722_benchmark_64VM.txt, c6166_20090727.patch,
> c6166_20090728.patch, c6166_20090810.patch, c6166_20090811.patch, graph.r,
> graph.r, Rplots-laptop.pdf, Rplots-nehalem32.pdf, Rplots-nehalem64.pdf,
> Rplots.pdf, Rplots.pdf, Rplots.pdf
>
>
> Got some ideas to improve CRC32 calculation.
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