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Yet Another Novice Tries To Write AGo Program/ Move Undo Data Structure And Algorithm
Sub-page of YetAnotherNoviceTriesToWriteAGoProgram

I gleaned this from Bruce Wilcox's discussion of RiscIgo. He describes his move structure as:

  • Color (1 bit)
  • Location (9 bits)
  • Ko Flag (1 bit)
  • Kill Directions (4 bits)
  • Plus 1 unused bit = 16 bits

What caught my eye is Kill Directions. How can 4 bits be enough information to replace captured stones upon undo? Ah, well of course! You just flood fill starting at the adjacent empty point(s).

[Diagram]
Capture

W1 is:

  • Color: White
  • Location: B18
  • Ko:no
  • Kill Directions: North (or East), South

[Diagram]
Undo

To undo this move, just flood fill with opposite color from the North (n) and South (s) points and then empty the location.


[Diagram]
Undo

Nifty!



This is a copy of the living page "Yet Another Novice Tries To Write AGo Program/ Move Undo Data Structure And Algorithm" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.