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Subject: Re: The Code for the Rybka-Mate-Bug

Author: Dann Corbit

Date: 16:25:38 12/14/05

Go up one level in this thread


On December 14, 2005 at 19:18:28, Uri Blass wrote:

>On December 14, 2005 at 18:53:21, Dann Corbit wrote:
>
>>On December 14, 2005 at 08:00:00, Vasik Rajlich wrote:
>>
>>>On December 14, 2005 at 04:44:15, Steve Maughan wrote:
>>>
>>>>Vasik,
>>>>
>>>>>The problem is when the hash entry ages.
>>>>
>>>>This is easy to get around - just store the distance to mate from the *position*
>>>>(i.e. not the root) in the hash table.
>>>>
>>>>In pseudo code:
>>>>
>>>>procedure push_hash(position)
>>>>begin
>>>>	if winning_mate_value_in_hash then
>>>>		hash_draft_depth += position's_ply_from_root
>>>>	else if losing_mate_value_in_hash then
>>>>		hash_draft_depth -= position's_ply_from_root
>>>>	store(position)
>>>>end;
>>>>
>>>>procedure probe_hash(position)
>>>>begin
>>>>	if found_in_table(poistion) then
>>>>	begin
>>>>		get_hash(position)
>>>>		if winning_mate_value_in_hash then
>>>>			hash_draft_depth -= position's_ply_from_root
>>>>		else if losing_mate_value_in_hash then
>>>>			hash_draft_depth += position's_ply_from_root
>>>>	end
>>>>end;
>>>>
>>>>I hope this helps!
>>>>
>>>>Regards,
>>>>
>>>>Steve
>>>
>>>Steve,
>>>
>>>thanks, I guess this also works - although it's a bit dirty.
>>
>>What's the other way to do it?
>
>see my post in
>
>http://www.talkchess.com/forums/1/message.html?470096

Can't the same position (therefore) have a huge number of different scores then
(depending on where we saw it in the tree)?

Tbis way seems more complicated to me.



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