On Thu, Oct 16, 2003 at 11:26:11AM +0200, Andreas.Schroeder@gillardon.de wrote:
1. how can i do performance tests if the tests are small? In imperative languages, you cycle through 1000 times and divide the runtime by 1000. How can i do something similar in haskell?
Even in an imperative language, running a fast calculation in a loop is a fishy way to run a timing. I'd say that whatever sort of language you're using, the best way to run a timing is always in the context of how you plan to actually use the routine. If it's so fast that you can't distinguish its time from that spent in the calling routine, it means you don't need to bother optimizing it. That being said, you you can pretty easily use map and fold to run a function a number of times and actually used. Whether you're using a functional language or an imperative one, in the presense of sufficiently smart compilers you always have to make sure your result is actually used in some way--otherwise the compiler could just skip the loop. In a lazy language like haskell, even if the compiler isn't smart, if the results aren't used it'll probably skip the loop. slow_function :: Double -> Double test max = sum $ map slow_function [0.0,0.001..max]
2. How do i get haskell to do something _without_ printing anything on the screen? For now, i do something like
main = do startt <- getCPUTime putStr $ (show testAIBD1) ++ ", " ++ (show testZins1) endt <- getCPUTime putStr $ "\tTook " ++ (show $ (endt - startt) `div` ((10^6) * 5)) ++ " ns\n"
where testAIBD1 is a sum of 40 calculation results and also is testZins1.
main = do startt <- getCPUTime when (testAIBD1 == a value) $ exitWith ExitSuccess when (testZins1 == a value) $ exitWith ExitSuccess endt <- getCPUTime putStr $ "\tTook " ++ (show $ (endt - startt) `div` ((10^6) * 5)) ++ "ns\n" Except that you probably need to give an input via the IO monad to testAIBD1, otherwise the compiler can determine at compile time that the equality is false and not bother generating any code for it. -- David Roundy http://www.abridgegame.org/darcs