I am using the Automatic Analysis function of Arena Chess. A great way to analyze many positions without human interaction. Arena produces an log-file with the result of an analysis. In the first line of a new position being analyzed there are three numbers, the middle one is a puzzle for me. Here an example output:

 1 - 0 1                
    Avoid move: 
    Best move (SF16): Ng1-f3
    Not found in: 00:00
     1/1    00:00.001            247    247k    +0.02   1.Nf3

In the first row, the leftmost 1 refers to the position count, the last number 1 is the move number, what is the 0 in the middle? The number in the middle is not always 0, other values are often seen too.

1 Answer 1


I found the answer. It is the Halfmove clock; the number of halfmoves since the last capture or pawn advance, used for the fifty-move rule.

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