Re: Pgcc in Deb
On Mon, Apr 03, 2000 at 11:35:08AM +0300, Eray Ozkural wrote:
> I disagree. From experience, I know that up to %50 speedup can be gained
> in number crunching stuff. I'd suspect %20 could be pretty normal for
> most CPU hungry apps, and the overall speedup would be significant.
Please post full information when you make claims like this. Code,
compiler versions and options, /proc/cpuinfo, ... We hear these claims a
lot - it's apparent that you haven't scanned the archives for the last time
this topic came up.
The numbers I ran on povray (a compute intensive task) don't show any
significant (-ly larger than the deviation between independent
measurements) speedups using a variety of -mcpu and -march options.
For instance, the best time for a K6/300 when compiled for i486 was 3
seconds (1.5%) faster than when compiled or scheduled for k6. Actually
scheduling for "pentium" had the most noticeable effect, and
that was a slowdown.
Real Pentium (R)'s seem to have weird scheduling requirements compared to
other ix86 platforms (bother newer and older), but scheduling for i486 (the
default) does as well as anything else. No other platform
(PII/Celeron/K6/486) showed significant variation with cpu/arch flags.
It would be interesting to add K7, the newer PIII's, and pgcc to these
benchmarks, but they'd all have to be rerun so that the exact same binaries
were used on all platforms (a big hassle). Until gcc 2.96 is released I see
little point in retesting for architecture differences. IIRC from my brief
tests of pgcc a while back it didn't perform as well as the then current
egcc anyway. The egcc speedup over gcc272 was around 10%.