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I was studying about minmax algorithms and it said the branching factor of a chess game is around average 35. Meaning a player can move about 35 legal moves per position.

I am not able to comprehend this.Like if I do the opening in chess I was able to count 20 possible legal moves.(1 or 2 possible moves for 8 pawns that gives us 16. 2 possible for 2 knights respectively giving a total of 20)

So how it was calculated?

Shad
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    The initial position is very unusual. Why would you expect it to have about the average number of available moves? – David Richerby Sep 06 '16 at 15:54
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    And what does this have to do with computer science? – David Richerby Sep 06 '16 at 15:55
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    Count the moves after 1. e4 e5. – gnasher729 Sep 06 '16 at 19:01
  • It might be connected to Computer Science, slightly, and would be more on-topic if it was more about Minimax, I didn't knew there is chess site, but it appears there are also some related questions about chess branching factor, but this also makes the question even less on-topic here in the current form. – Evil Sep 06 '16 at 21:57
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    The connection witih computer science may be related to movement tree. In the book "Artificial Intellige: A Modern Aproach", the authors said that in average, the branch factor of 35, but I can`t found why in the book. In the internet, I found a number of 31 over 2.5 millions game analysis. With branch factor of 35 and a usual game going with 80 movements, there are 10^123 possible positions in the game, while observable universe has only 10^80 atoms as stimation. Make a computer play chess is a good problem for computer science. – Welyab Paula Oct 08 '23 at 23:57

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Since the moves differ per turn it was calculated as the average. Yes you are right, there are exactly 20 moves in the first turn, but after advancing with knights, bishops, rooks and queen into the center of the board the number of legal moves is increasing and since it is average of the minimax tree also the situation after encrouning with several queens on the both sides is calculated (not very wise game, but still perfectly valid to have more than 100 available moves in one turn.

Please check for some more legal chess positions.

Evil
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