Dear ghc-5.00.1 (binary, linux, i386-unknown), Here are some information on performance that may occur useful. Choose n, run test n in various modes and compare the timings. It consists mainly of merge sorting of a list of Int-s combined with reversing. The particular points I find are * ghc -interactive runs the compiled with -O code 1.4 times slower than it is for the batch mode and needs considerably larger minimal heap to obtain the result. * the performace difference between -O and -Onot looks small. ----------------- Serge Mechveliani mechvel@botik.ru -- statistics for test 55000 ------------------------- ghc-5.00.1 -interpreted time (under large heap) = 13.3 sec, minimal-needed(Heap -M...) = 12Mb compiled with -O -fvia-C -O2-for-C, loaded and run from -interactive time = 3.1, min(Heap) = 9Mb linked and run in batch mode 2.2 5Mb -Onot, run from -interactive 3.8 10Mb ghc-4.04 -Onot time for -M9m -H8m = 3.5 sec. -------------------------------------------------------- module CompPlatf (test) where -- main = putStr $ shows (test 55000) "\n" test :: Int -> Int test n = max' $ sort' $ zipWith (-) (reverse xs) xs where xs = [1..n] max' :: Ord a => [a] -> a max' [x] = x max' (x:y:xs) = case compare x y of LT -> max' (y:xs) _ -> max' (x:xs) sort' :: Ord a => [a] -> [a] sort' xs = s $ mergePairs [[x] | x <- xs] where s [] = [] s [xs] = xs s xss = s $ mergePairs xss mergePairs (xs:ys:zss) = (merge xs ys):(mergePairs zss) mergePairs xss = xss merge :: Ord a => [a] -> [a] -> [a] merge [] ys = ys merge xs [] = xs merge (x:xs) (y:ys) = case compare x y of GT -> y:(merge (x:xs) ys) _ -> x:(merge xs (y:ys))