[computer-go] How to cache local tactical searches?

[Chrilly]

Thanks for the pointer to the article.
The article is very interesting, but its not about local search. I assum you mean the indexing scheme which is better than plain-vanilla bitboards.

Chrilly


  ----- Original Message ----- 
  From: Peter Drake 
  To: computer-go 
  Sent: Monday, July 31, 2006 6:21 PM
  Subject: Re: [computer-go] How to cache local tactical searches?


  You might try the method I used for caching the result of life-and-death searches in a recent paper:


  http://www.lclark.edu/~drake/go/icai2006-final-drake.pdf


  Peter Drake
  Assistant Professor of Computer Science
  Lewis & Clark College
  http://www.lclark.edu/~drake/








  On Jul 31, 2006, at 1:29 AM, Chrilly wrote:


    The eval of Suzie has a ladder-searcher which I plan now to extend to Geta's and simple 3-Liberty Problems. Although the ladder-code is reasonable fast, in more complicated positions the speed of the eval goes down considerable due to the local tacitical search. So far I use the most primitive cache method. A hash-table with the global hash-code. Due to iterative deeping there are some cache-hits, but the percentage is much lower than with a more clever cache-scheme.
    One idea is that the local search marks a Dirty-Bitmap. All the intersection which have been visited (and probably also the neighbours of the visited stones, because e.g. the status of a ladder-breaker depends also on its liberties). The dirty Bitmap and the current Board-Bitmaps are stored. When the local search is called again, the old result is used, if the new board matches the stored one on the intersections of the dirty bitmap.
    I do not know if the method works in case of ladders at all, e.g. the liberties of a ladder breaker can depend on a stone in a completly other part of the board. Its not my intention to have a perfect ladder code. The question is, if the idea is flawed at all and not only in some tricky special cases.
    A also do not know if the BitMap Key is the best way. I am not really satiesfied with this idea. One has to store 3 Bitmaps and also the comparision is relative slow (but of course much faster than doing the search again). Any other suggestions?


    Chrilly 
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