Re: [Cooker] compiler flags
Karl Mitchell [EMAIL PROTECTED] writes: It's possibly also worth noting that Athlon/Duron chips optimise best on -O1 at present under gcc-2.95. I don't know why. -Karl better with -O1 than with -O2 or superior!?? -- Guillaume Cottenceau -- Distribution Developer for MandrakeSoft http://www.mandrakesoft.com/~gc/
Re: [Cooker] compiler flags
Antony Suter [EMAIL PROTECTED] writes: Guillaume Cottenceau wrote: till, you should use: export CXXFLAGS="-O3 -fomit-frame-pointer -fno-exceptions -fno-rtti -pipe -s -mpentium -mcpu=pentium -march=pentium -ffast-math -fexpensive-optimizations" I think that this is in error. I understand from gcc 2.95 documentation that only one of the flags -m, -mcpu and -march need be specified. My understanding is that:- "-mcpu=pentium" specifies to optimise for the pentium but allow to run on other cpus. "-march=pentium" specifies to optimise fully for the pentium, dropping compatibility for other cpus. actually the basic flags for mdk rpm's is: -march=pentium -cpu=pentiumpro it is supposed to: . use opcodes of Pentium . schedule for PentiumPro titi wanted to do that because this should optimize good for P-2 and P-3, since this architecture is close to ppro but far from pentium. however let's note i had to do -march=pentium for some c++ code such as gtkmm and clanlib, because gcc has a bug which prevents from successful linkage with that parameter. -- Guillaume Cottenceau -- Distribution Developer for MandrakeSoft http://www.mandrakesoft.com/~gc/
Re: [Cooker] compiler flags
Guillaume Cottenceau wrote: Karl Mitchell [EMAIL PROTECTED] writes: It's possibly also worth noting that Athlon/Duron chips optimise best on -O1 at present under gcc-2.95. I don't know why. -Karl better with -O1 than with -O2 or superior!?? Faster with -O1 than -O2 or -O3 under almost all criteria for speed. I can't remember the source though and the figures I've got (below) aren't a good comparison. If you replace -O1 with -O3 on test B (below) you'll see what I mean. By the way, I would urge against using gcc -ffast-math, as it can cause actual errors in floating point routines. I am a numerical modeller and I found for one of my floating point iterative routines the cumulative error was a few percent in one case. This could have been more to do with the version of egcs I was using, but I doubt it. Admittedly this doesn't matter for all programs, but perhaps something like 'octave' would suffer? Cheers, -Karl A) CFLAGS = -s -static -Wall B) CFLAGS = -s -static -Wall -O1 C) CFLAGS = -s -static -O3 -fomit-frame-pointer -Wall -mpentiumpro -march=pentiumpro -fforce-addr -fforce-mem -malign-loops=2 -malign-functions=4 -malign-jumps=2 -funroll-loops -fexpensive-optimisations -malign-double -fschedule-insns2 -mwide-multiply Based on K6-233 Index Mem Index Integer index FP Index A 1.349 1.014 1.824 B 3.605 2.284 5.003 C 3.609 3.245 7.175 -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-Karl Mitchell=-=-=-=-=-=-=-=-=-=-=-=-=-=- | Dept. of Geomatic Engineering |Secretary, ISPRS WG IV/5 | | University College London | "Extraterrestrial Mapping"| | Gower Street, LONDON WC1E 6BT | +44 (0)20 7504-2744| [EMAIL PROTECTED]=-=-==-=-=-=-=-=-=-=-=- "Science is like sex: sometimes something useful comes out, but that is not the reason we are doing it" -- Richard Feynman
Re: [Cooker] compiler flags
Karl Mitchell [EMAIL PROTECTED] writes: [...] better with -O1 than with -O2 or superior!?? Faster with -O1 than -O2 or -O3 under almost all criteria for speed. I can't remember the source though and the figures I've got (below) aren't a good comparison. If you replace -O1 with -O3 on test B (below) you'll see what I mean. By the way, I would urge against using gcc -ffast-math, as it can cause actual errors in floating point routines. I am a numerical modeller and I found for one of my floating point iterative routines the cumulative error was a few percent in one case. This could have been more to do with the version of egcs I was using, but I doubt it. Admittedly this doesn't matter for all programs, but perhaps something like 'octave' would suffer? I don't know precisely why this has been chosen. I think this is because, this is default parameters, and packagers are supposed to override them when needed. [...] A) CFLAGS = -s -static -Wall B) CFLAGS = -s -static -Wall -O1 C) CFLAGS = -s -static -O3 -fomit-frame-pointer -Wall -mpentiumpro -march=pentiumpro -fforce-addr -fforce-mem -malign-loops=2 -malign-functions=4 -malign-jumps=2 -funroll-loops -fexpensive-optimisations -malign-double -fschedule-insns2 -mwide-multiply Based on K6-233 Index Mem Index Integer index FP Index A 1.349 1.014 1.824 B 3.605 2.284 5.003 C 3.609 3.245 7.175 I don't understand. You did not explain the numbers: I suppose than B is faster than A because there is no optim for A. So given this, I interpret your numbers are "speed index" (opposed to "time consumed"), e.g. the greater the faster. So, For all three things, C is faster than B. Why do you say -O1 is faster than -O2, then? Is it something to do with the other parameters? (so why did you put other parameters for C..!?) -- Guillaume Cottenceau -- Distribution Developer for MandrakeSoft http://www.mandrakesoft.com/~gc/
Re: [Cooker] compiler flags
Guillaume Cottenceau wrote: Karl Mitchell [EMAIL PROTECTED] writes: [...] better with -O1 than with -O2 or superior!?? Faster with -O1 than -O2 or -O3 under almost all criteria for speed. I can't remember the source though and the figures I've got (below) aren't a good comparison. If you replace -O1 with -O3 on test B (below) you'll see what I mean. By the way, I would urge against using gcc -ffast-math, as it can cause actual errors in floating point routines. I am a numerical modeller and I found for one of my floating point iterative routines the cumulative error was a few percent in one case. This could have been more to do with the version of egcs I was using, but I doubt it. Admittedly this doesn't matter for all programs, but perhaps something like 'octave' would suffer? I don't know precisely why this has been chosen. I think this is because, this is default parameters, and packagers are supposed to override them when needed. [...] A) CFLAGS = -s -static -Wall B) CFLAGS = -s -static -Wall -O1 C) CFLAGS = -s -static -O3 -fomit-frame-pointer -Wall -mpentiumpro -march=pentiumpro -fforce-addr -fforce-mem -malign-loops=2 -malign-functions=4 -malign-jumps=2 -funroll-loops -fexpensive-optimisations -malign-double -fschedule-insns2 -mwide-multiply Based on K6-233 Index Mem Index Integer index FP Index A 1.349 1.014 1.824 B 3.605 2.284 5.003 C 3.609 3.245 7.175 I don't understand. You did not explain the numbers: I suppose than B is faster than A because there is no optim for A. So given this, I interpret your numbers are "speed index" (opposed to "time consumed"), e.g. the greater the faster. So, For all three things, C is faster than B. Why do you say -O1 is faster than -O2, then? Is it something to do with the other parameters? (so why did you put other parameters for C..!?) -- Guillaume Cottenceau -- Distribution Developer for MandrakeSoft http://www.mandrakesoft.com/~gc/ Probably he is referring to an article appeared on cpureview showing that sometimes on K7 -O1 would produce better results than -O2 or more. Those index seems the Byte index benchmark. Definitively I think we should do better benchmark for K7, Duron maybe using ssbench benchmark http://nastol.astro.lu.se/~stefans/bench.html Volunteers? I remember that we've already choosen to avoid -ffast-math for mathematical packages (gnuplot, octave, etc.). Maybe we should explicitely use it into the spec files, sort of CFLAGS="$RPM_OPT_FLAGS -fno-fast-math"? Bye. Giuseppe.
Re: [Cooker] compiler flags
On Fri, 25 Aug 2000, Antony Suter wrote: I think that this is in error. I understand from gcc 2.95 documentation that only one of the flags -m, -mcpu and -march need be specified. My understanding is that:- "-mcpu=pentium" specifies to optimise for the pentium but allow to run on other cpus. "-march=pentium" specifies to optimise fully for the pentium, dropping compatibility for other cpus. That's it. The cpu= stuff provides optimal instruction ordering for Pentiums (note that this same order differs for PPro and upper!) whereas the arch= introduces arch specific instructions. I think that it is non optimal to specify both -mcpu and -march at the same time. Well, it is - for Pentiums. Ppros run fine with it too, at least faster than without any of these. I don't know what the -mpentium is for. Oh, one last thing: using fast-math is tricky, especially for apps expecting full IEEE compliance. Try at all possible NOT to use it. -- Francis Galiegue, [EMAIL PROTECTED] "Programming is a race between programmers, who try and make more and more idiot-proof software, and universe, which produces more and more remarkable idiots. Until now, universe leads the race" -- R. Cook
Re: [Cooker] compiler flags
It's possibly also worth noting that Athlon/Duron chips optimise best on -O1 at present under gcc-2.95. I don't know why. -Karl -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-Karl Mitchell=-=-=-=-=-=-=-=-=-=-=-=-=-=- | Dept. of Geomatic Engineering |Secretary, ISPRS WG IV/5 | | University College London | "Extraterrestrial Mapping"| | Gower Street, LONDON WC1E 6BT | +44 (0)20 7504-2744| [EMAIL PROTECTED]=-=-==-=-=-=-=-=-=-=-=- "Science is like sex: sometimes something useful comes out, but that is not the reason we are doing it" -- Richard Feynman
Re: [Cooker] compiler flags
Francis Galiegue wrote: On Fri, 25 Aug 2000, Antony Suter wrote: I think that this is in error. I understand from gcc 2.95 documentation that only one of the flags -m, -mcpu and -march need be specified. My understanding is that:- "-mcpu=pentium" specifies to optimise for the pentium but allow to run on other cpus. "-march=pentium" specifies to optimise fully for the pentium, dropping compatibility for other cpus. That's it. The cpu= stuff provides optimal instruction ordering for Pentiums (note that this same order differs for PPro and upper!) whereas the arch= introduces arch specific instructions. I think that it is non optimal to specify both -mcpu and -march at the same time. Well, it is - for Pentiums. Ppros run fine with it too, at least faster than without any of these. I don't know what the -mpentium is for. I am still not sure what is optimal (when im compiling only for my own machine). It is best to specify both -mcpu=pentiumpro and -march=pentiumpro for my Pentium III machine? Oh, one last thing: using fast-math is tricky, especially for apps expecting full IEEE compliance. Try at all possible NOT to use it. Its a standard option for cross compiling the kernel in mdk 7.1 (im not sure about cooker). All the mandrake kernels ive seen, in source code form, specify all three of -m, -mcpu and -march. Also the kernels specify them multiple times in different places with multiple instances of other flags as well. So the kernel ends up with long redundant option strings on the gcc compile line. -- - Antony Suter ([EMAIL PROTECTED]) "Examiner" openpgp:71ADFC87 - "And how do you store the nuclear equivalent of the universal solvent?"
