[erlang-questions] native

Tony Rogvall tony@REDACTED
Tue Sep 11 08:57:20 CEST 2012

On 10 sep 2012, at 14:41, Thomas Lindgren <thomasl_erlang@REDACTED> wrote:

>> I started playing with a simple implementation of MD5 (basically straight from the wiki page) 
>> When the implementation produce the correct output, I did some timing for fun and also
>> tried to native compile it. 
>> To my astonishment I discovered that the code was slower when native compiled.
>> I am using R15B01 on mac.  Can this be true? And in this case why? 
>> Note that I do not care to optimize the implementation it self! I am more interested why
>> the native compiler produce slower code on this example.
> On my Mac, the best native result 7% is faster than the best beam result. But the timing varies by 20% from run to run, so I think the proper claim is they are about the same. (I also think Hipe ought to comfortably beat Beam on this sort of code.)
Good to know. On my computer all runs I have tried so far has been slower in native compile.
I could not believe my eyes.
So, everything is good then ? ;-)


> Unfortunately, 'pp_native' gave broken/confusing output so it's hard to trace what happens. The arithmetic looks like it's being inlined, which ought to provide a boost. There are calls to r/1 and rotate/2 in the inner loop (md5_/6) which possibly should have been inlined.
> Best,
> Thomas

"Installing applications can lead to corruption over time. Applications gradually write over each other's libraries, partial upgrades occur, user and system errors happen, and minute changes may be unnoticeable and difficult to fix"

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