Author: Dave Gomboc
Date: 22:48:45 12/31/02
Go up one level in this thread
On January 01, 2003 at 01:44:59, Dave Gomboc wrote: >On January 01, 2003 at 01:03:14, Robert Hyatt wrote: > >>On December 31, 2002 at 23:03:03, Dave Gomboc wrote: >> >>>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; >>>> >>>>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; >>>> >>>>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. >>>> >>>>If I assume that the condition x>=0 happen in most of the cases then it seems >>>>clear that A[x]=1 is faster. >>>> >>>>Uri >>> >>>Referencing A[-1] will likely give you intermittent problems that are hard to >>>track down. If you really think you can't afford the check, though, then do >>>something like this (C++ code below:) >>> >>>int PADDED_A[102]; >>>... >>>const int & A = PADDED_A+2; >>> >>>Now you can reference A[i] where i is an int in the range -2 to 99 without >>>trashing memory that doesn't belong to you. AFAIK this hack technically invokes >>>undefined behaviour, but it's safer than not having the padding at all, where >>>you might change the value of another variable by accident. Personally, I'd >>>just test for the condition. >>> >>>Dave >> >> >>I assume you mean const int *A = PADDED_A + 2; >> >>:) > >Yep, whoops. :-) > >Dave No, wait a sec, that's wrong too! Correct is: int PADDED_A[102]; ... int * const A = PADDED_A+2; I want A itself to be const, not the stuff that A is pointing to. Dave
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