Vector API reproducibility bug (?)

[Xiaohong Gong]

>

> I think what you are observing for your whole project is the difference between execution of the Vector API expressions in the interpreter and execution of the optimized code produced by C2. In the former, Math::acos will be used, in the latter an SVML-derived implementation will be used.

>



Is this a bug that different runs on the same system may get different results?



> (It may be possible to fix this difference between the interpreter and

> C2 for the vector operations, but it would some work to do so.)

>



OK, do you have a plan to fix this difference?



Thinking about such kind of optimization for AArch64, I noticed that there were some questions about the code quality and maintainability of SVML assembly [1]. As John also mentioned about other possible alternatives [2], my colleague pointed me a good project, SLEEF [3], which looks promising in terms of portability, quality and performance [4]. (I don't know much about license compatibility with OpenJDK.)





[1] https://github.com/openjdk/jdk/pull/3638

[2]

https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2021-May/047336.html

[3] https://sleef.org/

[4] https://sleef.org/benchmark.xhtml

Thanks,
Xiaohong Gong
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