Author: Tanya Deborah
Date: 19:48:28 12/14/05
Go up one level in this thread
On December 13, 2005 at 11:52:03, Álvaro Begué wrote:
>On December 13, 2005 at 08:47:51, Chrilly Donninger wrote:
>
>>Just for the curious, below is the code for the Rybka-Mate bug. I have seen
>>another bug in the Beta-Code too. There are in every programm hundreds of bugs,
>>so it would be more surprising to say: I have seen no other bug.
>>
>>.text:0040CD07 mov ebp, [esp+868h+var_854]
>>.text:0040CD0B cmp ebp, 0FFFF810Ch
>>.text:0040CD11 mov dword_667A14, edi
>>.text:0040CD17 jnz loc_40CDCA
>>.text:0040CD1D mov eax, [esp+868h+arg_C]
>>.text:0040CD24 neg al
>>.text:0040CD26 pop edi
>>.text:0040CD27 pop ebx
>>.text:0040CD28 pop esi
>>.text:0040CD29 pop ebp
>>.text:0040CD2A sbb eax, eax
>>.text:0040CD2C and eax, 0FFFF8300h
>>.text:0040CD31 add esp, 858h
>>.text:0040CD37 retn
>>
>>In C this reads as:
>>if(Bestscore == -32500( // No legal move found
>> if(InCheck) {
>> return -32000;
>> }
>> else { // Stalemate
>> return 0;
>> }
>>}
>>
>>The bug is, that all mates are the same. In fact shorter mates are better for
>>the mate-giving side (or worse for the mated side) than longer mates. One has to
>>subtract the Plies/Distance from the starting position.
>>The bug is in my opinion a consequence of a bad design decision. There are 2
>>different "minus-infinite" values. In BestScore minus infinite is -32500, for
>>mate its -32000. If one sets bestscore at the first place to -32000+Ply one gets
>>cleaner and more efficient code and avoids the bug.
>>I had the same bug in Nimzo 1.0. But I must admit, that Rybka 1.0 is stronger.
>>
>>Chrilly
>
>
>I use the exact same solution that Chrilly proposes, combined with the "store
>only bounds for mating scores in the hash table" idea that I picked from Bruce
>Moreland's website. As far as I can tell, it works great.
>
>Álvaro.
Hi Alvaro.
Sorry for my question, (because it is not about chess) Did you worked in a new
Torquemada version in all this time?
There are some news about a new Spanish program?
Thanks in advance
Regards
Tanya Deborah
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