Author: Michael Neish
Date: 21:58:42 02/02/00
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On February 03, 2000 at 00:04:38, Dan Newman wrote: > >I first tried bitboards maybe 2 yrs ago and decided they'd be a good deal >slower than (say) 0x88. I tried a few experiments in move generation that >seemed to indicate bitboard move generation was about half the speed I could >get with 0x88, so I concentrated on 0x88 and got what I thought were fair >results (aprox. 130 knps on a P6/200 with almost no eval). Then I decided to >try bitboards again--just for the heck of it--and now find that I'm now >getting much better performance than I thought possible--much better than >with 0x88. (I'm running just under 500 knps on a P3/500 with quite a few >eval terms thrown in too.) Very interesting reply, thanks for your time. I'm still a novice at this computer programming business, so pardon me, but what is 0x88? I'm using CodeWarrior on the Mac. On a 300MHz G3 I'm getting about 50 knps which I think is pretty pathetic. For starters, the BSF and BSR operations don't work here; I have to replace them with CNTLZW (count leading zeroes word) which means that, because it applies to words only, I have to test each half of the bitboard individually and shift 32 bits in between. I'm not sure how much slower this is, but as the most often-used routine in the program it must surely have some measurable effect. >The change is due in part to using the BSF and BSR operations for doing >first_one() and last_one() instead of the C++ code I had been using, and >also in part to the compiler I'm using now (MSVC 5.0). (I had been using >Watcom, and with Watcom the bitboard code is a bit slower than the 0x88. >I think some of this is due to the way I'm getting at the BSF and BSR >operations in MSVC vs Watcom.) Really very interesting. I had no idea that different compilers could make such a big difference in performance. Thanks for the comments. Mike.
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