Author: Robert Hyatt
Date: 10:24:00 02/19/04
Go up one level in this thread
On February 19, 2004 at 12:15:18, Frank Phillips wrote: >On February 19, 2004 at 08:56:27, Frank Phillips wrote: > >>On February 19, 2004 at 08:12:32, Dieter Buerssner wrote: >> >>>On February 18, 2004 at 20:45:32, Robert Hyatt wrote: >>> >>>>How are you testing? IE when I use intel's compiler, with PGO, the inline is >>>>faster here. Not significantly, but still faster... >>> >>>I used gcc without PGO (was too lazy to do the profile run). I added >>>-DINLINE_ASM to the CFLAGS and removed the asm= for the linux target. First I >>>had removed -DUSE_ASSEMBLY, but that didn't compile, because then the versions >>>in boolean.c would also be compiled. So, I added the DUSE_ASSEMBLY again (and >>>ignored the warning about static declaration follows extern declaration, which >>>IMO does not really matter). I did not use icc, because it says: >>> >>># -INLINE_ASM Compiles with the Intel assembly code for FirstOne(), >>># LastOne() and PopCnt(). This is for gcc-style inlining >>># and thoroughly breaks the Intel C/C++ compiler at the >>># present (version 8.0). >>># >>> >>>in the Makefile. >>> >>>Regards, >>>Dieter >> >> >>Does it (LastOne()/FirstOne) work in gcc (version 3.3.1 Mandrake Linux 9.2 >>3.3.1-2mdk) on an AMD XP? >> >>I get very different node counts, for a fixed depth search, compared to the >>array lookup method. It does not seem to work at all on Intel 8.0 as you say. >>Could be a bug in my program of course, but I have not found it yet. There were >>two places I called LastBit() with an empty array, but this was harmless - and I >>changed it. >> >>Frank > > >The different inlinex86.h version in 19.11 works. > >Array look-up still faster for me on an AMD XP. > >Frank The code has always worked with an input of zero, so that isn't a problem. I had inadvertently left the old inlinex86.h (or inlineasm.h whatever it was called) in the source distribution even though I never used it in a production sense. It was just an experiment done while participating in a discussion here on CCC a few months ago, about the apparently slowness of the cmovxx instruction on current Intel hardware. It had one known bug that Dieter pointed out (one clobbered register that the compiler might overlook although I would hope that with a dynamic register allocation scheme, it would notice the register was getting zapped). So anything could happen depending on the compiler. When I tried the old inline code on intel, it just choked and puked. The new inline asm works better. When you say array lookup is still faster, are you talking about firstone/lastone or popcnt or all three? bsf/bsr have always been the fastest for me on any platform...
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