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{-# LANGUAGE ParallelArrays #-}
{-# OPTIONS -fvectorise #-}
module QuickHullVect (quickhull) where
import Types
import Data.Array.Parallel
import Data.Array.Parallel.Prelude.Double
import qualified Data.Array.Parallel.Prelude.Int as Int
import qualified Prelude as P
distance :: Point -> Line -> Double
distance (xo, yo) ((x1, y1), (x2, y2))
= (x1-xo) * (y2 - yo) - (y1 - yo) * (x2 - xo)
hsplit :: [:Point:] -> Line -> [:Point:]
hsplit points line@(p1, p2)
| lengthP packed Int.< 2 = singletonP p1 +:+ packed
| otherwise
= concatP [: hsplit packed ends | ends <- [:(p1, pm), (pm, p2):] :]
where
cross = [: distance p line | p <- points :]
packed = [: p | (p,c) <- zipP points cross, c > 0.0 :]
pm = points !: maxIndexP cross
quickHull' :: [:Point:] -> [:Point:]
quickHull' points
| lengthP points Int.== 0 = points
| otherwise
= concatP [: hsplit points ends | ends <- [: (minx, maxx), (maxx, minx) :] :]
where
xs = [: x | (x, y) <- points :]
minx = points !: minIndexP xs
maxx = points !: maxIndexP xs
quickhull :: PArray Point -> PArray Point
{-# NOINLINE quickhull #-}
quickhull ps = toPArrayP (quickHull' (fromPArrayP ps))
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