[Vm-dev] 3 Bugs in LargeInteger primitives

Stefan Marr smalltalk at stefan-marr.de
Sat Sep 1 20:49:14 UTC 2012


Hi Nicolas:

On 01 Sep 2012, at 22:15, Nicolas Cellier wrote:

> I just tried on a stack VM (MacOSX core 2...), and I get different
> measurements, at most 3% penalty, not 20%

Sorry, the 20% claim is based on wrong assumptions...
In short, I don't know what the penalty is on microbenchmarks.

I was only checking the benchmark results here:
  http://soft.vub.ac.be/~ppp/codespeed/changes/?tre=5&rev=5e18a83ed285c900aacd4190f91df6627d9ccc01&exe=1&env=2
The corresponding patch is here:
  https://github.com/smarr/RoarVM/commit/5e18a83ed285c900aacd4190f91df6627d9ccc01

As you can see, the IntLoop benchmark is taking a pretty strong hit.
I was not cross-checking what the benchmark actually does, unfortunately.
I was just assuming it does multiplication, which would explain the hit, but it does only do subtraction.

So, actually, I don't know.
The benchmark is not measuring that primitive, and the other benchmarks are looking ok (taking measurement errors into account).

Still wonder what's wrong with the IntLoop benchmark thought. 20% for perhaps a new offset in the binary for related code, sounds like a lot.


Best regards
Stefan


-- 
Stefan Marr
Software Languages Lab
Vrije Universiteit Brussel
Pleinlaan 2 / B-1050 Brussels / Belgium
http://soft.vub.ac.be/~smarr
Phone: +32 2 629 2974
Fax:   +32 2 629 3525



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