Re: computer-go: Sharing Go modules

["Magnus Persson" <magnus.persson@xxxxxxxxxx>]

Well here is number 4 (a variant) :-)

> The coordinate coding method that I use is X,Y converts to X+Y*20. The
> arrays are all 421 long where all te points at 0,Y and X,0 contain special
> values to make it easy to detect the edge of the board. This is a convenient
> coding since it's still fairly easy to see which coordinates they represent
> (for example: 63 is 3,3 and 356 is 16,17). However I do realise that every
> Go programmmer has their own idea of how this should be done and that
> there's little chance that I can convince everyone in the world to use this
> scheme (that would be nice though <grin>) instead of using separate X and Y
> coordinates.

I use the same way of accessing an one-dimensional array except that 
I have two layers of border data, because I once thought that i would 
need to access a points two spaces away from a given point without 
having to check any boundaries.

In practice I almost never do that (I only look at points one space 
away) so every array I use in my program spends a lot of memory (and 
since all my array big enough to hold 21x21 boards they are rather 
large).

The only drawback I have experienced is in patternmatching - because 
the way I do it is necessary to work with x,y coordinates, and check 
for boundaries.

I also often uses bitmaps to store logical information about points 
visited etc. And then you also need to make a conversion from index 
to coordinates, using division that is slow. I solved that by table 
look up. For each point in the one-dimensional array there is a pair 
of integer in a table that tells me which line (32-bit word) a column 
(bit) is corresponding bit in the bitmap.

I personally love this way of representing the board since two 
variables (x,y) make the code longer and much harder.

One nice thing I do is to keep increments in an array such that I can 
jump around in a given pattern from a given point. In Pascal it looks 
like this.

--------
var
  p: boardoffset;
begin
  for u := 0 to 3 do
  begin
    Inc(p, URDL[u]); // UpRightDownLeft
    DoSomething(p);
  end;
end;

--------

Best wishes 
Magnus
--
Magnus Persson
Department of psychology, Uppsala University
Box 1225, SE-751 42, Sweden
018-471 2141 (work), 018-460264 (home)
070-2987879 (cellular)
MAILTO: magnus.persson@xxxxxxxxxxxxxxxxx
URL: http://www.docs.uu.se/~magnuspe