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https://issues.apache.org/jira/browse/HADOOP-5598?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Scott Carey updated HADOOP-5598:
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Attachment: PureJavaCrc32.java
This version of PureJavaCrc32.java significantly beats, or equals, the native
implementation. For small chunks, it is far faster. For large chunks it is
equal.
This version is simply a term expansion of the previous one, and it operates
four bytes at a time.
There is a way to nearly double this one more time for large chunks, but it is
proving tricky to nail down correctly.
> Implement a pure Java CRC32 calculator
> --------------------------------------
>
> Key: HADOOP-5598
> URL: https://issues.apache.org/jira/browse/HADOOP-5598
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Reporter: Owen O'Malley
> Assignee: Todd Lipcon
> Attachments: crc32-results.txt, hadoop-5598-evil.txt,
> hadoop-5598-hybrid.txt, hadoop-5598.txt, hadoop-5598.txt, PureJavaCrc32.java,
> TestCrc32Performance.java, TestCrc32Performance.java
>
>
> We've seen a reducer writing 200MB to HDFS with replication = 1 spending a
> long time in crc calculation. In particular, it was spending 5 seconds in crc
> calculation out of a total of 6 for the write. I suspect that it is the
> java-jni border that is causing us grief.
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