RE: computer-go: Super-Ko

["Grajdeanu, Adrian" <adrian.grajdeanu@xxxxxxx>]

if the hash key is (or roughly is) the number of stones on the board, then
the two versions are equally costly in terms of time.

> -----Original Message-----
> From: John Tromp [mailto:tromp@xxxxxxxxxxxxxxxxx]
> Sent: Friday, 13 July, 2001 09:39
> To: computer-go@xxxxxxxxxxxxxxxxx
> Subject: Re: computer-go: Super-Ko
> 
> 
> > About Super-Ko
> > 
> > How much speed will it take out of a program, 
> > if for every move the total numbers of stones actual on the 
> board is counted and stores in an array,
> > and the Super-Ko is only checked with the prevous board 
> position where the count of stones is equal to the present position ?
> 
> That's still neither as simple nor as fast as looking up the 
> current boardhash
> in a hashtable. E.g. in java you can just define a
> 
>   HashSet oldboards = new HashSet();
> 
> and a new move will violate superko if
> 
>   oldboards.add(board.zobristHash()) == false
> 
> (add() returns true if its argument is not already present)
> this will take constant time.
> 
> regards,
> 
> %!PS                       %  -John Tromp (http://www.cwi.nl/~tromp/)
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