Author: Robert Hyatt
Date: 22:01:24 12/31/02
Go up one level in this thread
On December 31, 2002 at 20:32:28, Uri Blass wrote: >On December 31, 2002 at 19:50:43, Robert Hyatt wrote: > >>On December 31, 2002 at 17:49:52, Uri Blass wrote: >> >>>From Ed programmer stuff >>> >>>Killer-One [current ply] 110 >>>Killer-One [current ply-2] 108 >>>Killer-Two [current ply] 106 >>>Killer-Two [current ply-2] 104 >>> >>>I until today used only >>> >>>Killer-One [current ply] >>>Killer-Two [current ply] >>> >>>I am interested to know if using 4 killers is a new idea or maybe this idea is >>>known to be used by other programs. >> >>It was known in 1975. Chess 4.0 used this. You can find it mentioned in >>the chess 4.7 chapter of "Chess Skill in Man and Machine." >> >>We did that in Cray Blitz, but we also did more killers, going back to the >>root in fact... >> >> >> >>> >>>I did try part of the idea that Ed suggested without clear results. >>> >>>I changed the order of moves in movei to >>> >>>Killer-One [current ply] >>>Killer-One [current ply-2] >>>Killer-Two [current ply] >>> >>>instead of >>> >>>Killer-One [current ply] >>>Killer-Two [current ply] >>> >>>I found that it is better only in part of the cases and have not clear results >>>if it is better or worse than previous order but I had a bug in the >>>implementation and I checked killer[ply-2] even in cases when ply-2<0. >>> >>>It is surprising that the program did not crush and even performed better in >>>part of the cases. >>> >>>I still do not use check bound software. >>>I asked in a previous discussion about checking bounds but I solved the >>>problem that caused me to ask about it and I also read a claim that if a >>>varaible is out of bound the program should crush. >>> >>>I also looked for a software that will help me under visual C++ but after I >>>asked to get it for free evaluation and I only got an email that suggest me to >>>contact them by fax or telephone I did not respond(I responded by email but my >>>email was blocked for some reason and I decided that the subject is probably not >>>very important). >>> >>>I think now that it may be important because a chess program may even play well >>>inspite of the fact that it calls killer[-1] so it is possible that I have more >>>mistakes like that. >>> >> >>That probably won't hurt a thing. That move probably would not pass your >>legality check, so even a garbage move would just waste a tiny bit of time >>as you notice it is not legal in the current position. > >Yes but I can still imagine problems. > >1)If I am unlucky a garbage move may be legal so it can be counterproductive. > >2)I thought that garbage may do something worse than giving a random >number. >I thought that if my program try to look at some place that does not exist the >program may crush and not give me a random number or may change another array. > >I also cared not to have -1 > A[x]=1; and not >if (x>=0) >A[x]=1; That doesn't hurt a thing. a[-1] is one "thing" before a[0]. If a is an integer, a[-1] is simply 4 bytes in front of a[0]... > >If you are right then it means that there are cases when I can save time by >doing something like > >A[x]=1; instead of >if (x>=0) >A[x]=1; You can do that just so you _know_ what is in front of A. IE in fortran, arrays go from 1 to N, rather than 0 to N-1 as in C. But in Cray Blitz we wanted to reference a[i] where i could be 0, 1, ... and all we did was make sure that there was a memory word that could safely be zapped, in front of a[1]. We did it like this: common /x/ dummy, a(10) a(1) thru a(10) are normal array references. a(0) actually stores on top of "dummy". > >The point is that if I understand correctly then I understand from your post >that a[x]=1 when x=-1 can not change relevant information. No, it can _definitely_ change something, just not exactly what you think it is changing. :) It will change what is in _front_ of the array. In C, the only way to know what is in front of the array is to put the array in a structure, and then put something right in front of that array declaration to declare the "dummy" space needed for a[-1]. Or a[-2] if you want to go backward even farther. > >If I assume that the condition x>=0 happen in most of the cases then it seems >clear that A[x]=1 is faster. Correct. If you know that -1 <= x <= N, then one dummy word in front of the array will let you eliminate the test. > >Uri
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