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From "Zhenyu Zheng (Jira)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-23133) Numeric operations can have different result across hardware archs
Date Tue, 12 May 2020 09:25:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-23133?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zhenyu Zheng updated HIVE-23133:
--------------------------------
    Status: Open  (was: Patch Available)

> Numeric operations can have different result across hardware archs
> ------------------------------------------------------------------
>
>                 Key: HIVE-23133
>                 URL: https://issues.apache.org/jira/browse/HIVE-23133
>             Project: Hive
>          Issue Type: Sub-task
>            Reporter: Zhenyu Zheng
>            Assignee: Zhenyu Zheng
>            Priority: Major
>         Attachments: HIVE-23133.1.patch, HIVE-23133.2.patch, HIVE-23133.3.patch, HIVE-23133.4.patch,
HIVE-23133.5.patch
>
>
> Currently, we have set up an ARM CI to test out how Hive works on ARM platform:
> [https://builds.apache.org/view/H-L/view/Hive/job/Hive-linux-ARM-trunk/]
> Among the failures, we have observed that some numeric operations can have different
result across hardware archs, such as:
> [https://builds.apache.org/view/H-L/view/Hive/job/Hive-linux-ARM-trunk/25/testReport/org.apache.hadoop.hive.cli/TestCliDriver/testCliDriver_vector_decimal_udf2_/]
> [https://builds.apache.org/view/H-L/view/Hive/job/Hive-linux-ARM-trunk/25/testReport/org.apache.hadoop.hive.cli/TestSparkCliDriver/testCliDriver_subquery_select_/]
> [https://builds.apache.org/view/H-L/view/Hive/job/Hive-linux-ARM-trunk/25/testReport/org.apache.hadoop.hive.cli/TestSparkCliDriver/testCliDriver_vectorized_math_funcs_/]
> we can see that the calculation results of log, exp, cos, toRadians etc is slitly different
than the .out file results that we are
> comparing(they are tested and wrote on X86 machines), this is because of we use [Math
Library|https://docs.oracle.com/javase/6/docs/api/java/lang/Math.html] for these kind of calculations.
> and according to the [illustration|https://docs.oracle.com/javase/6/docs/api/java/lang/Math.html]:
> _Unlike some of the numeric methods of class StrictMath, all implementations of the equivalent
functions of class Math are not_
> _defined to return the bit-for-bit same results. This relaxation permits better-performing
implementations where strict reproducibility_
> _is not required._
> _By default many of the Math methods simply call the equivalent method in StrictMath
for their implementation._
> _Code generators are encouraged to use platform-specific native libraries or microprocessor
instructions, where available,_
> _to provide higher-performance implementations of Math methods._
> so the result will have difference across hardware archs.
> On the other hand, JAVA provided another library [StrictMath|https://docs.oracle.com/javase/6/docs/api/java/lang/StrictMath.html]
that will not have this kind of problem as according to its' [reference|https://docs.oracle.com/javase/6/docs/api/java/lang/StrictMath.html]:
> _To help ensure portability of Java programs, the definitions of some of the numeric
functions in this package require that they produce_
> _the same results as certain published algorithms._
> So in order to fix the above mentioned problem, we have to consider switch to use StrictMath
instead of Math.
>  
>  
>  



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