Author: James Robertson
Date: 21:23:56 10/24/99
Go up one level in this thread
On October 24, 1999 at 23:18:32, Robert Hyatt wrote: >On October 24, 1999 at 16:02:34, Frank Schneider wrote: > >>On October 24, 1999 at 10:08:45, Robert Hyatt wrote: >> >>>On October 24, 1999 at 05:59:40, Frank Schneider wrote: >>> >>>> >>>>I haven't tried the 'strings lapetite.exe', but I believe you that there are >>>>lots of strings that were just translated. I agree that is strong evidence >>>>that lapetite's I/O is based on Crafty. But is there any evidence that the >>>>engine is still a crafty clone? >>>> >>>>Copying an engine is, from my point of view, much worse than reusing the >>>>I/O stuff and structure of the userinterface. >>>> >>> >>>Run the second test I mentioned: start "La Petite" under a debugger, and >>>look for the area where all the 64 bit masks are in memory. You will find >>>patterns like 80000000 00000000, 40000000 00000000, 20000000 00000000, etc. >>>then look for the rotated masks which are like the above, but in a different >>>order (64 bits, 1 bit set). Then compare to crafty.exe. Look at data.c to >>>find the pre-initialized scoring array patterns. See if you can find 'em in >>>La Petite. :) >>> >>>etc. >>I don't have La Petite. >> >>But I have very similar bit masks in Gromit (only 16 bit, because Gromit >>does not use bitboards) and I wonder how to write a bitboard-base program >>without such bit masks. Is there anything special about the order of masks >>in Crafty that is unlikely to be invented independently by others? > >there are 64 of the masks that are just 1 bit shifted right slowly but surely. >I can't imagine why you would have such masks (notice that they are each 64 >bits long) if you aren't doing bitmaps. I have another set that has one bit >set in each 64 bit value, but the bit isn't in the 'sliding' pattern, as it is >used to update the rotated-left-90-degree board. Another set of 64 for each >of the two 45-degree-rotated boards. Those are pretty unique to my style of >rotating... There are many other masks as well, including the compact-attacks >array of values that _nobody_ would likely have without using the crafty engine >(this was the code done by Mark Bromley). > > > >> >>Do other bit board based programs use such masks? How do they look in >>Inmichess? Insomniac (if it uses bit boards)? > >any bitboard program probably has the 64 masks with the sliding 1, but the >other 3 sets are very unlikely, and the compact-attack stuff is probably >impossible to reproduce exactly without copying, as there are so many >different ways to do the same thing. > I think it is not _that_ unlikely. My rotated bitboard code was written with a lot of English (and a little code) advice from Tim Diamond (thanks Tim!). He basically explained in _great_ detail how rotated bitboards work, and I implemented them with original code. I didn't use the Crafty source at all for the early part of my program (I do peek at it sometimes now, and have gotten a lot of ideas from it. Thanks Bob! :). I have the masks with 1 bit shifted, and they should look identical to Crafty's, Arasan's, GLChess's, and Galahad's. I have two arrays that simply have set bits for any square a knight or king attacks from a certain square. I'll bet all the programs I mentioned have these exact arrays (it seems the easiest way to generate knight and king moves to me). If they use 0 for A1, the arrays should? look identical in memory. As for your rotated masks, they were an integral part of Tim's method (which I presume he learned from you....?), so I have them too. :) I was poking around in Arasan many months back and thought I saw similar masks in Jon's program. Don't know if mine would line up in memory with yours, but they serve the same or a similar purpose. Beyond this, I believe you are right. I would be _shocked_ if any programmer invented the same mobility, evaluation, etc. etc. etc. arrays invented by any other programmer. James > > > >> >>I agree that it is something different if LaPetite uses the same scoring arrays. >>Everyone uses them, but finding lots of identical scores would be surprising. >> >> >>I'd really like to see a statement here, where G. Mueller gives her point >>of view. >> >> >>Frank > > >So would I. Because it is so blatant. But G. Mueller didn't discuss voyager >a year ago when she burst upon the scene with a program stronger than almost >any new amateur, complete with parallel search... I doubt we will hear anything >now...
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