Author: Robert Hyatt
Date: 08:01:39 03/08/06
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On March 07, 2006 at 00:09:58, Stuart Cracraft wrote: >On March 06, 2006 at 22:53:05, Dann Corbit wrote: > >>Lot's of programs have a problem with this one. It's a sacrifice leading to a >>forced mate. I would not worry about this one too much: >>[D] 4r1k1/p1qr1p2/2pb1Bp1/1p5p/3P1n1R/1B3P2/PP3PK1/2Q4R w - - bm Qxf4 > >Of course you're right but I'm still hopeful some day I can solve >things like that. I think I remember Bob talking about WAC 141. Here is what I believe is the correct way to use WAC for testing: (1) do _not_ do the one second per position run. You don't get much information there, and if a change doesn't get you more or less right answers, you get no info at all. (2) I have an "early exit" option when I run a test that says "if, at the end of N consecutive iterations, the correct (key) move has been found to be best, stop the search immediately, regardless of how much time has been used." I run the test with this value set to 1, so that when an iteration completes, if the right move is best, I quit and go to the next position. Take the times for each of the 300 positions, square them and then sum the result. Any change you make that reduces this number is good. Any change you make that increases this number is bad. Even if you get one more right, but now every position takes longer to solve, you hurt your tactical ability. The sum-of-squares is the easiest way to detect this. Otherwise suppose you get the same number right on two consecutive runs, and suppose you only have three positions in the suite and you get them all right. The first run, the times are 4, 4, and 2. The second run (changed code) gives you 3, 3 and 5. Which is better? I'd rather have the first (sum of squares = 36) rather than the latter (sum of squares = 43). For reference for times, on my 750 laptop, crafty gets 265 correct out of 300. On a single 2.8ghz xeon, it gets 285 right. using two cpus it gets 294 right. I have an 8-way opteron run that got 300 right in 1 sec/move but that is with extreme hardware. An older version saw 300 right at 1 sec per move on a dual alpha, run by Tim Mann, 3-4 years ago. I still have the log I believe... Yes, here is the summary: (this a dual 21264, do not know the speed) total positions searched.......... 300 number right...................... 300 number wrong...................... 0 percentage right.................. 100 percentage wrong.................. 0 total nodes searched.............. 236973211.0 average search depth.............. 4.5 nodes per second.................. 1783641 One caution, I can (and have) tuned Crafty to do better than this. But if you are not careful, you can kill real game performance as WAC likes check extensions, recapture extensions, etc. While real games might show those to waste excessive nodes and result in worse play OTB.
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