[Computer-go] Computing CFG distance in practice

[Fuming Wang]

how to calculate CFG distance?

Fuming

On Tue, Jan 25, 2011 at 3:49 AM, Brian Sheppard <sheppardco at aol.com> wrote:

> I use CFG distance only in the tree. The playout uses the concept
> "adjacent"
> which is trivial to compute.
>
> The only distance I am concerned about is the distance to the last move,
> and
> there are only 4 classes: distance 1,2,3, and >3. So it is cheap.
>
> The advantage is in semeais. Moves at CFG distance 3 are the outside
> liberties of the opponent's string.
>
> There was not a big difference compared to the other two heuristics. I
> found
> that
>
> - CFG is best
> - max(dx, dy) + (dx + dy)/2 is second best
> - Manhattan is third.
>
> Brian
>
> -----Original Message-----
> From: computer-go-bounces at dvandva.org
> [mailto:computer-go-bounces at dvandva.org] On Behalf Of Jacques Basaldúa
> Sent: Monday, January 24, 2011 2:41 PM
> To: computer-go at dvandva.org
> Subject: [Computer-go] Computing CFG distance in practice
>
> Hi,
>
> I got a lot of improvement recently (something you all
> did long time ago) with proximity heuristics. I am using
>
> Manhattan distance:
>   d = max(dx, dy)
>
> and
>   d = max(dx, dy) + (dx + dy)/2
>
> where dx = abs(ex - ox) and dy = abs(ey - oy)
>
> But many people report CFG distance to be superior.
>
> What do you do:
>
> a. Compute it in root. Then build a lookup table and
> use the LUT during playouts and tree search.
>
> b. Compute the shortest path from (ox, oy) to (ex, ey)
> connected by the stones on the board each time you need
> to evaluate a distance.
>
> I don't like a because it looks inefficient as the
> board changes a lot during the search.
>
> I don't like b because it looks computing intense
> unless there is some smart idea I am missing.
>
>
> Jacques.
>
>
>
>
>
>
>
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