In message <[EMAIL PROTECTED]> you wrote:
>
> I was searching for the best mcpu option for amcc440, compiling and
> running a small program you can find here:
> http://magnux.free.fr/gcc/mandelbrot.c. My distro is a ppc fedora core 6, and
> results are obviously the same using DENX4.0.
In general, you should need to meddle much with such options; the ELDK
default settings are usually OK.
> --------------------
> -bash-3.00# gcc -O2 ./mandelbrot.c -o ./mandelbrot && time ./mandelbrot && rm
> -f ./mandelbrot
>
> real 1m15.059s
> user 1m14.996s
> sys 0m0.060s
> -bash-3.00# gcc -O2 -mcpu=440 ./mandelbrot.c -o ./mandelbrot && time
> ./mandelbrot && rm -f ./mandelbrot
>
> real 0m39.606s
> user 0m39.552s
> sys 0m0.028s
> -bash-3.00# gcc -O2 -mcpu=440fp ./mandelbrot.c -o ./mandelbrot && time
> ./mandelbrot && rm -f ./mandelbrot
>
> real 1m15.016s
> user 1m14.988s
> sys 0m0.024s
> -bash-3.00# gcc -O2 -msoft-float ./mandelbrot.c -o ./mandelbrot && time
> ./mandelbrot && rm -f ./mandelbrot
>
> real 0m39.577s
> user 0m39.544s
> sys 0m0.032s
This looks to me as if you have been runing all these tests in the
SAME environment, probably the /opt/eldk/ppc_4xx root file system,
which is soft-float based. You must not do this.
For tests with FP instructions, you MUST use the /opt/eldk/ppc_4xxFP
root file system. For tests with soft-float, you MUST use the
/opt/eldk/ppc_4xx root file system.
You CANNOT link an application build with one settings against
libraries using other settings, or you will run into trouble. You
would probably have seen the problems if you had used any test where
the results of the calculations would have been visible.
> * I do not explain why not using FPU gives better results ?
Because you did not run the tests you thought yoiu were running.
> * mcpu option seems to not have any effect ?
Use "gcc -v" to see exactly which options get passed to the compiler
stages.
> * My third test was to compile and run mplayer.
> - With default options (no mcpu specified), my test mpeg was smooth.
> - With mcpu=440fp, my test mpeg was not smooth.
>
> Can anybody bring me some lights about the right gcc mcpu option for amcc440
> ?
Just use the defaults, unless you know exactly what you are doing.
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office: Kirchenstr. 5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: [EMAIL PROTECTED]
If there was anything that depressed him more than his own cynicism,
it was that quite often it still wasn't as cynical as real life.
- Terry Pratchett, _Guards! Guards!_
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