Author: Peter McKenzie
Date: 19:50:41 12/08/99
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On December 08, 1999 at 20:03:41, Dann Corbit wrote: >On December 08, 1999 at 19:56:04, Bruce Moreland wrote: > >>On December 08, 1999 at 18:28:26, Dann Corbit wrote: >> >>>On December 08, 1999 at 17:16:28, Luis E. Alvarado wrote: >>> >>>>I agree with you 100%. Humans tend to be far more inconsistent than computers. >>> >>>You might be surprised. Computers will play a real stinker move some times. >>>Could be an unknown hash collision. Could be a bad opening book entry. Could >>>be a program bug or just an inferior algorithmic decision. But for whatever >>>reason, computers screw up now and again, in a big way. >> >>I have never seen evidence of a hash collision causing a game to be lost. I >>have seen people suggest this as a reason for losing when a particularly bad >>clunker is made, but this suggestion is always made before investigation and >>never after. >> >>In college I used to do a lot of programming in a large open area full of a >>bunch of crazy people, on a minicomputer that we all shared. I noticed that >>whenever one particular guy had a bug, he would tell us all to save our work, >>because he believed that the mini was behaving strangely and was about to crash. >> >>This is the same sort of deal I think. >> >>Most bad moves are produced as a result of the program working as designed, and >>responsibility for this falls on the shoulders of the programmer. >Hash collisions are so improbable that it would be very difficult to pinpoint >that as the problem. But if you shrink the hash tables to 10K or so, I suspect >the problems will show up frequently if not handled correctly [which brings up >the point -- how do you handle hash collisions?]. Every increase in size will >make collisions less likely, but even with a terabyte a collision is possible. >That collision could cause a key choice to be made incorrectly. It's just not >very likely. According to my reasoning, shrinking the size of the hash table will probably make a hash collision less likely. I am assuming that by 'hash collision' you mean having two different positions hashing to the same hash key. This can cause a problem if the following series of events happen: (a) reach position A, with hash key X, store a hash record H in the table (b) reach position B which is different to A but has same hash key Y (c) retrieve hash record H which has a score that is nonsensical for position B I would think that the chance of the above happening decreases with smaller tables. The reason being that between (a) and (b), the chance that hash record H gets overwritten will increase dramatically in a small hash table.
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