[Computer-go] Semeais

[Petr Baudis]

  Hi!

On Thu, Jan 13, 2011 at 12:52:58PM +0100, Kahn Jonas wrote:
> By the way, has anybody tried the most basic way to settle semeais in
> playouts? I mean:
> * Spot semeais (not basic at all, but probably necessary for almost all
> approaches).

  I think one problem is, most programs use only chain information, not
group information (well, "group" is chain in Pachi lingo, but that is
rather unfortunate historical remnant) - then, in many cases part of an
eye will be considered a different group, etc. Another problem is that
during simulation, most programs do not judge chain _safety_ at all;
they do not check if it can live independently, is seki, is making
nakade within larger group (Pachi checks this newly now), or is in
semeai. The problem is, this kind of analysis is very expensive. It is
difficult to code it without many bugs in the first place, it will bias
the simulations even worse than now if inaccurate, and it is very slow
so it must work well even with small number of playouts.

  (Maybe Zen and Valkyria are doing high-level analysis like above,
though...)

  There is plenty of places where to put high level analysis. But it
takes a lot of time and the progress is slow. I'm myself rather trying
for more domain-independent techniques to address semeai - though I also
sense that likely, adding some stone safety analysis will be inevitable
for pro-level 19x19 performance in the end.


  (Yes, I guess I'm optimistic in the last few days ;-), but now I'm
rather convinced that MCTS can reach pro-level performance in a few
years; it scales well with hardware, and there is still huge amount
of research going on. The problem for most people I think is certainly
not a shortage of very promising ideas to try, but time to code them
and most importantly debug them - in my experience, that can easily take
10x the programming time, not just checking that the code finally does
what you want in the situation you want, but also all the crazy things
it does in variety of other situations.)

> * Play all the moves in the semeai before going to usual playouts.

  You forgot "in correct order". This can be also very complex
decision-making process.

-- 
				Petr "Pasky" Baudis
Computer science education cannot make an expert programmer any more
than studying brushes and pigment can make an expert painter. --esr