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From "Dmitry Chuyko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15033) Use java.util.zip.CRC32C for Java 9 and above
Date Tue, 14 Nov 2017 15:24:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15033?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16251538#comment-16251538
] 

Dmitry Chuyko commented on HADOOP-15033:
----------------------------------------

[~raviprak] I compared partial checksums over partial random array and byte buffer. Some more
details:
* Over 1000 elements (crc of 0 element, crc of 1 element...).
* Zero and non-zero offset.
* Interpreter, C1, C2 Hotspot compiler.
* OpenJDK 10-internal
* x86_64 and aarch64

CRC32C values required to be equal are equal.

> Use java.util.zip.CRC32C for Java 9 and above
> ---------------------------------------------
>
>                 Key: HADOOP-15033
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15033
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: performance, util
>    Affects Versions: 3.0.0
>            Reporter: Dmitry Chuyko
>
> java.util.zip.CRC32C implementation is available since Java 9.
> https://docs.oracle.com/javase/9/docs/api/java/util/zip/CRC32C.html
> Platform specific assembler intrinsics make it more effective than any pure Java implementation.
> Hadoop is compiled against Java 8 but class constructor may be accessible with method
handle on 9 to instances implementing Checksum in runtime.



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