Re: Two questions, -gp and why is it slow?

Hi Brandon,

Brandon Heller wrote:
> These times were from an unloaded P4 2.6Ghz with 512MB RAM and HT, yet the 
> times are much slower than the 1.5GHz 1.5GB RAM machine from Etienne's thesis 
> paper.  Is the sablecc benchmark heavily memory-dependent, have I missed a 
> 'debug' compiler switch, did the Simple C file change, or is something else to 
> blame for this discrepancy? 

There's nothing to blame on SableCC or SimpleC.  In SableVM, Classpath
and GCC, on the other hand, I see a few possible explanations (you would
need to actually perform tests to confirm any of these):
1- Because of changes in GCC, SableVM now turns off a few optimizations
to preserve inlinability of instructions.  This can affect negatively
the speed of the inlined engine.
2- It has been observed by some student of mine that some Classpath
merges have introduced slower class library code.  As we do not do class
library development, we haven't spend the necessary time to investigate
and identify the slowing code.

If you have the resources/time, you could actually try to run your
experiments with all SableCC versions 1.0.x and 1.1.x, and find any/all
performance regressions:
* 1.0.x
 http://prdownloads.sourceforge.net/sablevm/
* 1.1.* and later:
 http://sablevm.org/download/release/

IIRC, I used GCC 3.0 or 3.1 for my PhD experiments.  I think you can
expect different inlinability and/or prerformance with newer GCC
versions.  :-/

Please keep us informed of your findings. :-)

Hoping this helps,

Etienne

-- 
Etienne M. Gagnon, Ph.D.            http://www.info2.uqam.ca/~egagnon/
SableVM:                                       http://www.sablevm.org/
SableCC:                                       http://www.sablecc.org/

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