Author: Ricardo Gibert
Date: 21:37:52 06/17/05
Go up one level in this thread
On June 17, 2005 at 20:39:58, Ricardo Gibert wrote:
>On June 17, 2005 at 18:56:08, Vincent Diepeveen wrote:
>
>>On June 16, 2005 at 18:42:44, Vasik Rajlich wrote:
>>
>>>On June 16, 2005 at 13:31:39, Vincent Diepeveen wrote:
>>>
>>>>On June 16, 2005 at 05:22:26, Vasik Rajlich wrote:
>>>>
>>>>>On June 15, 2005 at 22:40:22, Tor Alexander Lattimore wrote:
>>>>>
>>>>>>Hi
>>>>>>Is it possible to use a single variable in the MTD(f) search? Something like
>>>>>>this:
>>>>>>
>>>>>>int MTD(int depth, int guess)
>>>>>>{
>>>>>> if (depth<1) return Evaluate();
>>>>>> MOVE move_to_search;
>>>>>> int best=-INFINITY;
>>>>>> GenMoves();
>>>>>> while (GetNextMove(&move_to_search))
>>>>>> {
>>>>>> PlayMove(move_to_search);
>>>>>> val = -MTD(depth - 1, -guess + 1);
>>>>>> UnPlayMove(move_to_search);
>>>>>> if (val>best)
>>>>>> {
>>>>>> best=val;
>>>>>> if (val>=guess)
>>>>>
>>>>>You missed a line here. Fail-hard is "return guess", fail-soft is "return val".
>>>>>
>>>>>Fail soft helps when you need to re-search, so it helps more in MTD (f) than
>>>>>PVS, and doesn't matter at all in pure alpha-beta.
>>>> ^^^^^^^
>>>>I guess you meant a small typo here. doesn't ==> does
>>>>
>>>
>>>Actually I just forgot about hash effects at the next iteration. Without those,
>>>the statement would be true .. (as far as I can see)
>>
>>The hashtable is the thing that is refuting so so many algorithms... ...one of
>>them is for example no-progress pruning. With a hashtable it is an incorrect way
>>to search.
>
>
>I've "reverse engineered" the no progress pruning algorithm and it does not
>depend on the transposition table. Unless I've somehow reverse engineered it
>"improperly," the idea appears to be 100% sound to me.
I've thought it over and I think understand what it is you're getting at now.
Interesting.
Thanks for making me think!
>
>
>>
>>>Vas
>>>
>>>>>
>>>>>Vas
>>>>>
>>>>>> }
>>>>>> }
>>>>>> return (best);
>>>>>>}
>>>>>>
>>>>>>perhaps there is something very wrong with this? or perhaps it's used already, I
>>>>>>just noticed that on Aske Plaat's site he always uses an Alpha-Beta search with
>>>>>>0 width windowed searches, but doesn't this do the same thing? Is using
>>>>>>fail-soft type algorithms used in MTD(f) since it could well help zoom into the
>>>>>>correct score sooner?
>>>>>>
>>>>>>Cheers
>>>>>>Tor
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