I think this is what I want. Thanks! So I might have to repeat this
a few hundred times to actually get a legal position?
- George
Implemented that and my test serie of number of rounds needed to generate
legal board position is quite expected.
count=111, count=36, count=28, count=20, count=14, count=150, count=78,
count=13, count=149, count=113, count=186, count=43
count=149, count=178, count=103, count=57, count=21, count=23, count=47,
count=25, count=221, count=44, count=82
So it is actually 1.2% according (
http://homepages.cwi.nl:80/~tromp/go/legal.html) .
So average is fortunately less than hundred, so it is quite usable.
t. Harri
----- Original Message -----
From: "George Dahl" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, July 09, 2007 8:55 AM
Subject: Re: [computer-go] creating a "random" position
On 7/8/07, Paul Pogonyshev <[EMAIL PROTECTED]> wrote:
George Dahl wrote:
> How would one go about creating a random board position with a uniform
> distribution over all legal positions? Is this even possible? I am
> not quite sure what I mean by uniform. If one flipped a three sided
> coin to determine if each vertex was white,black or empty, then one
> would have to deal with stones with no liberties somehow. Could those
> just removed?
As I remember from theory of probability, you can create such a uniformly
"random" position this way[1]:
1. create a really random position, i.e. traverse all intersection and
assign a black/white/empty state at random to each;
2. if it happens to be not legal, discard and repeat step 1.
I believe it should be very fast, and this mustn't be difficult to check.
I.e. rate of discards should be low enough for speed of algorithm to be
speed of step 1 times C, where C is small.
However, this will tend to give you very artificial-looking positions.
Whether it is fine for your use-case, you know better.
[1] http://en.wikipedia.org/wiki/Rejection_sampling
Paul
I think this is what I want. Thanks! So I might have to repeat this
a few hundred times to actually get a legal position?
- George
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