Am Sonntag, 13. September 2009 18:03:30 schrieb Csaba Hruska:
Hi! I've upgraded my haskell programs to opengl 2.4.0.1 and I've noticed massive (3X) slowdown. I did only type fixes on code. Is it normal?
I could reproduce this, but the slowdown was related to the OpenGL package only indirectly, the real cause were your type fixes. I had a look at your code, and you can quickly get back your previous performance by an evil 2-line hack: ----------------------------------------------------------------------------------------------- panne@spock:~/build/lambdacube> diff lambdacube.orig/Graphics/LambdaCube/Render.hs lambdacude/Graphics/LambdaCube/Render.hs 11a12
import Unsafe.Coerce 42c43 < m <- (newMatrix ColumnMajor $ map realToFrac $ toListsMat44 t) :: IO (GLmatrix GLfloat)
m <- (newMatrix ColumnMajor $ unsafeCoerce $ toListsMat44 t) :: IO
(GLmatrix GLfloat) ----------------------------------------------------------------------------------------------- As I said, this is evil and probably not the right way to fix you code. Your FloatType and OpenGL's GLfloat have the same runtime representation, so 'realToFrac' is a no-op at runtime, *but* 'map realToFrac' is not a no-op, at least not with GHC's current optimizer. To avoid creating the transformation matrices over and over again, you could e.g. use a GLmatrix for your Transformation type or use GLfloat directly in your Math module. In a nutshell: "map realToFrac" considered harmful. ;-) Cheers, S.