Hacker News Reader

Comment by Peaker | Hacker News Reader

The Why Functional Programming Matters[1] paper builds a minimax in a lazy functional language and then enhances it to an alpha-beta.

The minimax looks like:

  evaluate = maximize . maptree static . prune 5 . gametree

maximize finds the maximum value. static is a heuristic analysis of the value of the board. prune cuts the tree to a certain depth. gametree generates the infinite game tree.

The alphabeta is more complicated, but also fits well within a pageful.

[1]: http://www.cs.utexas.edu/~shmat/courses/cs345/whyfp.pdf

View on HN

I'm sure the OP would appreciate a Haskell implementation optimized for clarity (not for speed). I wonder how speedy that would be.

This is my attempt to translate from the functional OCaml version, focusing on elegancy. If you like to, please help me optimize it while retaining elegancy :) https://github.com/phuc/Score4-haskell/blob/master/Main.hs

Why not work with the code/examples in "Why FP matters"?

Actually, I very much appreciate the fact that he didn't - this way the comparison is more fair - and easier to follow for people new to functional programming (like me).

Well, I think it's nice to take the best representative of each language, and not some arbitrary point. That way the comparison is more meaningful, and people can learn more from the code.

Stay tuned. I will do the one in this paper once I have time ;)

Added to the repos - can you please provide your prefered optimization parameters to GHC ? e.g. a Makefile?

Hey ttsiodras, "ghc -O2 Main.hs" should be enough. I've updated the code a bit. It's now half F#'s execution time on my computer :)

Excellent. And committed - I will study your code, Haskell is next on my agenda :-)

So I updated my code to also print out debug. And Haskell now is almost 4 times faster than F# on my computer ;)

Hmm... the scores you printed are not correct (look at the two board edges):

C++: sh -c "time ./bin.release/score4 o53 y43 -debug" Depth 7, placing on 0, score:2 Depth 7, placing on 1, score:8 Depth 7, placing on 2, score:8 Depth 7, placing on 3, score:8 Depth 7, placing on 4, score:8 Depth 7, placing on 5, score:8 Depth 7, placing on 6, score:2 5

Your Haskell code:

sh -c "time ./score4.bin o53 y43 -debug" Depth 7, placing on 0, score 0 Depth 7, placing on 1, score 8 Depth 7, placing on 2, score 8 Depth 7, placing on 3, score 8 Depth 7, placing on 4, score 8 Depth 7, placing on 5, score 8 Depth 7, placing on 6, score 0 5

I'll try to see why your code miscalculates on the two borders, but I don't speak Haskell so don't expect much :-)

Hi ttsiodras, thanks for poiting out :D. I looked at the code and figured out where it went wrong. I discussed my problem further on https://github.com/phuc/Score4-haskell/issues/1. Btw I don't know whether Github notifies everytime I respond. I'm so inefficient at communicating, lol.

Reply on news.ycombinator.com