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Re: Do we get the other 15% performance back too?


Burkhard Militzer <militzer@llnl.gov> writes:

> Hello,
>
> As a fan of the C++ gnu compiler project, I would like to congratulate the 
> gurus on the recent performance increase probably coming from corrections 
> in the prefetch routines. My benchmark shows

-O3 does not use prefetching it all.

Can you destill some small testcase that shows the problems?

Andreas

> Processor/OS         Compiler/options             Time(sec)
> Pentium 4 1.7Ghz     pgCC -O3 -fast -Minline=3/4   8.27  
> Pentium 4 1.7Ghz     gnu g++ -O3 (2.95.2)          8.62  <-- fastest
> Pentium 4 1.7Ghz     Intel icpc 5.0 -O3            8.65  
> Pentium 4 1.7Ghz     gnu g++ -O3 (2.95.3)         10.94   
> Pentium 4 1.7Ghz     gnu g++ -O3 (3.2)            11.30  <-- new
> Pentium 4 1.7Ghz     gnu g++ -O3 (3.01)           15.09  <-- previous
>
> The improvement from 3.01 to 3.2 are significant but it their a way of 
> somehow getting the performance of 2.95.2 back?
>
> Anyway, great work! Thanks a lot,
>
> Burkhard Militzer
>
> For comparison:
>       						    
> DEC Alpha 1GHz       KCC kcc3.4d -O3               5.2   
> DEC Alpha 667MHz     KCC kcc3.4g2 -O3              8.4   
> DEC Alpha 667MHz     g++ -O3 (2.96?)              10.3   
> DEC Al-Linux 667Mhz  g++ -O3 (2.96?)              14.66  
> O2K R10000           KCC -O3 +K3 --no_exceptions  18.26
> IMB SP2 332MHz       KCC kcc3.4d -O3 +K3          27.56  
>
>

-- 
 Andreas Jaeger
  SuSE Labs aj@suse.de
   private aj@arthur.inka.de
    http://www.suse.de/~aj


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