[erlang-questions] native

[Thomas Lindgren]

>________________________________
> From: Kostis Sagonas <kostis@REDACTED>
>
>
>I do not know why Thomas thinks that HiPE should be able to confortably beat BEAM on this sort of code (care to elaborate?).  From a brief glance it seems to me that the code spends a lot of time in BIFs written in C (most notably list_to_tuple/1 and element/2, but also trunc/1, abs/1 and math:sin/1. All of these are outside the reach of the native code compiler.


The regular MD5 algorithm is basically a loop doing lots of integer arithmetic and bit operations as well as accessing a few arrays. This ought on the face of it to be quite amenable to native code compilation. I'm amazed that the implementation Tony used managed to get trunc/abs/sin into the inner loop, but that might as you say well explain the problem.

>
>> Unfortunately, 'pp_native' gave broken/confusing output so it's hard to trace what happens.
>
>Well, this happens because the HiPE compiler compiles in parallel by default (!).  If you want to see the native code in the non-scrambled version use:
>
>    c(md5, [native, {hipe, [no_concurrent_comp, pp_native]}]).


Well well, you learn something new every day.

Best,
Thomas