art with code


Branching factor generator

A function to generate a stream of tree branching factors to approximate a non-integer branching factor.

branches' x i sum =
let v = (if sum/i > x then floor x else ceiling x) :: Int in
v : branches' x (i+1) (sum+fromIntegral v)

branches n = branches' n 0 0

e_branches = branches (exp 1)
e_100000 = take 100000 $ e_branches
average l = sum l / fromIntegral (length l)
average $ map fromIntegral e_100000 == 2.71828

You could also write the average function as

average2 l = snd $ foldl (\(i, avg) e -> (i+1, (avg*(i-1) + e)/i)) (1, 0) l

average2 $ map fromIntegral e_100000

even though that is less accurate. You can use a similar trick for the branches' function to use a running average instead of a running sum.

branches2' x i avg =
let v = (if avg > x then floor x else ceiling x) :: Int in
v : branches2' x (i+1) ((avg*(i-1)+fromIntegral v)/i)

branches2 n = branches2' n 1 0
average $ map fromIntegral $ take 100000 $ branches2 (exp 1)

To generate a tree of wanted size out of the branching factor list, you'd have a tree generator that eats values off the list and generates tree nodes breadth-first. It is kind of a pain to write.
Post a Comment

Blog Archive

About Me

My photo

Built art installations, web sites, graphics libraries, web browsers, mobile apps, desktop apps, media player themes, many nutty prototypes, much bad code, much bad art.

Have freelanced for Verizon, Google, Mozilla, Warner Bros, Sony Pictures, Yahoo!, Microsoft, Valve Software, TDK Electronics.

Ex-Chrome Developer Relations.