[computer-go] a few more questions

[Álvaro Begué]

On Tue, May 13, 2008 at 4:22 PM, Carter Cheng <carter_cheng at yahoo.com> wrote:
>  2) When generating random variables for the case where the "values" of placing a stone on different points on the board are different. Are there good ways to throw and determine which point has been selected for the next move by the random player?

I can answer this. The best way I know of getting a random point with
different weights (proportional to probabilities) for each point is to
keep a sum of weights per row and a total sum of weights for the
entire board. These are easy to update dynamically when an individual
weight changes. In order to pick a point, start with a random number
between 0 and the total sum. Go down row by row subtracting the weight
of each row, until you would get a negative number. Then walk the row
subtracting the weight of each point until you would get a negative
number. The place where you stop is the selected point.

This method may not be very robust if you use floating-point numbers
to represent weights (because you can't rely on associativity of
addition), but it works fine if you use an integer type.

If the description is not good enough, I can write some C++ code for you.


Álvaro.