On Saturday 23 June 2007 12:05:01 Claus Reinke wrote:
try making ray_sphere and intersect' local to intersect, then drop their constant ray parameter. saves me 25%. claus
also try replacing that (foldl' intersect') with (foldr (flip intersect'))!
using a recent ghc head instead of ghc-6.6.1 also seems to make a drastic difference (wild guess, seeing the unroll 1000 for ocaml: has there been a change to default unrolling in ghc?).
Wow! Now I get: GHC: 15.8s OCaml: 14s g++: 10s That's very impressive, and more than I was expecting. I think it is worth noting that you are now comparing optimized Haskell to unoptimized OCaml though, so the OCaml has more "low-hanging optimization fruit". :-) At this point, the single most productive optimization for the OCaml is to evade the polymorphism and closure in the "intersect" function by inlining the call to "List.fold_left". This makes the OCaml basically as fast as the C++ on my machine: GHC: 15.8s OCaml: 10.6s g++: 10s let delta = sqrt epsilon_float type vec = {x:float; y:float; z:float} let zero = {x=0.; y=0.; z=0.} let ( *| ) s r = {x = s *. r.x; y = s *. r.y; z = s *. r.z} let ( +| ) a b = {x = a.x +. b.x; y = a.y +. b.y; z = a.z +. b.z} let ( -| ) a b = {x = a.x -. b.x; y = a.y -. b.y; z = a.z -. b.z} let dot a b = a.x *. b.x +. a.y *. b.y +. a.z *. b.z let length r = sqrt(dot r r) let unitise r = 1. /. length r *| r let rec intersect orig dir (l, _ as hit) (center, radius, scene) = let l' = let v = center -| orig in let b = dot v dir in let disc = sqrt(b *. b -. dot v v +. radius *. radius) in let t1 = b -. disc and t2 = b +. disc in if t2>0. then if t1>0. then t1 else t2 else infinity in if l' >= l then hit else match scene with | [] -> l', unitise (orig +| l' *| dir -| center) | scenes -> intersects orig dir hit scenes and intersects orig dir hit = function | [] -> hit | scene::scenes -> intersects orig dir (intersect orig dir hit scene) scenes let light = unitise {x=1.; y=3.; z= -2.} and ss = 4 let rec ray_trace dir scene = let l, n = intersect zero dir (infinity, zero) scene in let g = dot n light in if g <= 0. then 0. else let p = l *| dir +| sqrt epsilon_float *| n in if fst (intersect p light (infinity, zero) scene) < infinity then 0. else g let rec create level c r = let obj = c, r, [] in if level = 1 then obj else let a = 3. *. r /. sqrt 12. in let aux x' z' = create (level - 1) (c +| {x=x'; y=a; z=z'}) (0.5 *. r) in c, 3. *. r, [obj; aux (-.a) (-.a); aux a (-.a); aux (-.a) a; aux a a] let level, n = try int_of_string Sys.argv.(1), int_of_string Sys.argv.(2) with _ -> 6, 512 let scene = create level {x=0.; y= -1.; z=4.} 1.;; Printf.printf "P5\n%d %d\n255\n" n n;; for y = n - 1 downto 0 do for x = 0 to n - 1 do let g = ref 0. in for dx = 0 to ss - 1 do for dy = 0 to ss - 1 do let aux x d = float x -. float n /. 2. +. float d /. float ss in let dir = unitise {x=aux x dx; y=aux y dy; z=float n} in g := !g +. ray_trace dir scene done; done; let g = 0.5 +. 255. *. !g /. float (ss*ss) in Printf.printf "%c" (char_of_int (int_of_float g)) done; done -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. The OCaml Journal http://www.ffconsultancy.com/products/ocaml_journal/?e