On 23/09/2008, at 14:59, Roman Leshchinskiy wrote:
dotp :: [:Int:] -> [:Int:] -> Int dotp v w = I.sumP [: (I.*) x y | x <- v, y <- w :]
The way the vectoriser works at the moment, it will repeat the array w (lengthP v) times, i.e., create an array of length (lengthP v * lengthP w). This is quite unfortunate and needs to be fused away but isn't at the moment. The only advice I can give is to stay away from array comprehensions for now. They work but are extremely slow. This definition should work fine:
dotp v w = I.sumP (zipWithP (I.*) v w)
Actually, I didn't pay attention when I wrote this. The two are not equivalent, of course. Only the second one computes the dot product. With comprehensions, you'd have to write dotp v w = [: (I.*) x y | x <- v | y <- w :] I suspect that will perform reasonably even now. Roman