Author: Dann Corbit
Date: 17:38:05 10/11/05
Go up one level in this thread
On October 11, 2005 at 20:22:47, chandler yergin wrote:
>On October 11, 2005 at 19:55:12, Dann Corbit wrote:
>
>>From here:
>>http://www.albert.nu/programs/dperft/main.htm
>>
>>Searching the root position we have:
>>Depth Perft value
>>1 20
>>2 400
>>3 8902
>>4 197281
>>5 4865609
>>6 119060324
>>7 3195901860
>>8 84998978956
>>9 2439530234167
>>10 69352859712417
>>11 2097651003696806
>>
>>That means that an 11 ply search of the root position using mini/max takes:
>>2,097,651,003,696,806
>>That's two quadrillion nodes.
>
>It's not an evaluation from the Starting Position,
>it's an evaluation of every legal position in the game.
>White has 20 Possible moves for the first move.
That is the 1 ply perft from above.
>Black has 20 moves for the first move.
For each of the 20 moves, there are 20 responses. Hence the 400 moves for the
ply 2 perft up above.
>Each move and the response is considered 1 ply
No. Each move is considered one ply. Each response is considered one ply.
Each move and response is considered 2 ply, unless you do something interesting
like Junior does where single reply extensions do not get counted.
>The Program evaluates all the possible legal moves 1/2 ply at a time.
This is wrong. Plain and simple.
>This is 1 iteration.
>Simple as that..
We should make things as simple as possible, but no simpler. Perhaps we need to
define some basic terms.
From:
http://www.chess-poster.com/english/glossary.htm
We have this:
"Ply: One play in a Chess game -white or black, which is one half of one
complete move pair. Computers have the capability to consider the probable
result of an almost infinite number of move/countermove strategems against each
move made by a player (except for book openings). These levels of move
combinations are referred to as "plies" or half-moves in computer terminology."
From the PGN Standard:
"16.1.3.5: Halfmove clock
The fifth field is a nonnegative integer representing the halfmove clock. This
number is the count of halfmoves (or ply) since the last pawn advance or
capturing move. This value is used for the fifty move draw rule."
Now, sometimes the word ply is also called 'move', which can be confusing. But
it is just like saying: "It's your move..." which does not imply that they get
to move two times.
>;)
>Chan
>
>>
>>If you can find ANY chess engine that will search the root position and get to
>>11 plies I will be pretty astonished if the node count is 2097651003696806
>>{meaning that every node has been examined}.
>>
>>On a 2GHz computer (assuming we can examine a node in one cycle which is
>>probably optimistic by a factor of about 1000), that would take 1048825.5
>>seconds or 12 days. Since chess engines are not just doing a perft, I would
>>expect a full width 11 ply search to take a full year on the fastest AMD
>>multiple CPU computer that money can buy.
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