BOU.LI.NA. method for generation of random Chess960 positions

 

This 3-step method ensures that all 960 starting positions have an equal probability to appear. It is considered to be the simplest method to produce a random Chess960 initial position. It uses 8 playing cards, separated in odds and evens.

Playing_card_club_1 Playing_card_club_3 Playing_card_club_5 Playing_card_club_7

Playing_card_club_2 Playing_card_club_4 Playing_card_club_6 Playing_card_club_8

 

Step 1: Randomly pick one card from each stack. These first two cards are the positions for the two Bishops. 

Obviously there will be one white and one black Bishop. For example, suppose the 5 and the 6 were drawn :

Playing_card_club_6 Playing_card_club_5

 

After placing the two Bishops accordingly :

Chess960 randomly generated position after step 1

Chess960 randomly generated position after Step 1

 

Step 2: Shuffle the remaining 6 cards and draw 3 random cards. These are the positions for the Queen and the 2 Knights.

In our example the remaining cards are 1, 2, 3, 4, 7, 8. Let’s say we drew the 2, 1 and 8, in this order:

Playing_card_club_2 Playing_card_club_1 Playing_card_club_8

 

The new position will be :

bview (2)

Step 3: The remaining empty squares are for Rook, King, Rook, in this order, so that castling is possible both ways.

After placing the last pieces, we get the following position :

Chess960 randomly generated position after step 3

Chess960 randomly generated position after Step 3

 

And the full starting position will look like this :

Chess960 randomly generated position displayed in full

Chess960 randomly generated position displayed in full

 

The BOU.LI.NA. method was devised by Boussios Christos, Likartsis Athanasios and Navrozidis Georgios (hence the name).

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