On Sun, 10 Aug 2003 11:12, you wrote: > I decided to spend a few hours experimenting with compiler options in > Gentoo last night. I wanted to measure the performance difference of > "optimal" compiler settings. I built Gentoo from stage 1 with the > following options: Expressing an opinion here, I think that you would see a much greater difference in performance if the test/benchmark programs were 'deep math' applications. All the proggies following have a fair amount os disk i/o while the computer is sitting there just waitng for the data to come off of the disk. This will seriously mask any effect of code optimisations. In general the faster the cpu, the less overall benefit you will see from optimisations. Perhaps you might care to repeat the tests with something like POVray rendering a relatively complex scene on a less than up to the moment cpu.
Also it's fairly well documented, in the lore if nowhere else, that the use of '-O3' can sometimes be rather counter productive on some chip sets. Unfortunatly I know not what. > "Optimal" settings, based on Gentoo documentation: > CFLAGS="-march=athlon-mp -O3 -pipe -fomit-frame-pointer" > CHOST="i686-pc-linux-gnu" > > "Base" settings: > CFLAGS="-O2" > CHOST="i386-pc-linux-gnu" > > The configuration of the system was exactly the same other than the > above settings. I initially built the system with the "optimal" > settings, performed a benchmark, then rebuilt the entire system with the > "base" settings. [ ... ] -- Sincerely etc., Christopher Sawtell
