Hi, Firstly, Happy New Year! Secondly, I've written (and improved using other solutions I've found on the net) a simple sudoku solver which I'm trying to profile. Here is the code: import Array import List (transpose, nub, (\\)) import Data.List data Sudoku = Sudoku { unit :: Int, cells :: Array (Int, Int) Int, holes :: [(Int, Int)] } cell :: Sudoku -> (Int, Int) -> Int cell s i = (cells s) ! i instance Read Sudoku where readsPrec _ s = [(Sudoku unit cells holes, "")] where unit = length . words . head . lines $ s cells = listArray ((1, 1), (unit, unit)) (map read . words $ s) holes = [ c | c <- indices cells, (cells ! c) == 0] instance Show Sudoku where show s = unlines [unwords [show $ cell s (x,y) | x <- [1 .. unit s]] | y <- [1 .. unit s]] genNums :: Sudoku -> (Int, Int) -> [Int] genNums s c@(i,j) = ([1 .. u] \\) . nub $ used where used = (row s u i j) ++ (col s u i j) ++ (square s sq u i j) u = unit s sq = truncate . sqrt . fromIntegral $ u row s u i j = [cell s (i, y) | y <- [1 .. u]] col s u i j = [cell s (x, j) | x <- [1 .. u]] square s sq u i j = [cell s (x, y) | y <- [1 .. u], x <- [1 .. u], f x i, f y j] where f a b = div (a-1) sq == div (b-1) sq solve :: Sudoku -> [Sudoku] solve s = case holes s of [] -> [s] (h:hs) -> do n <- genNums s h let s' = Sudoku (unit s) ((cells s) // [(h, n)]) hs solve s' main = print . head . solve . read =<< getContents When I compile as such: $ ghc -O2 --make Sudoku.hs -prof -auto-all -caf-all -fforce-recomp and run it on the following puzzle: 0 2 3 4 3 4 1 0 2 1 4 0 0 3 2 1 I get the following profiling report: Fri Jan 1 10:34 2010 Time and Allocation Profiling Report (Final) Sudoku +RTS -p -RTS total time = 0.00 secs (0 ticks @ 20 ms) total alloc = 165,728 bytes (excludes profiling overheads) COST CENTRE MODULE %time %alloc CAF GHC.Handle 0.0 10.7 CAF Text.Read.Lex 0.0 2.1 CAF GHC.Read 0.0 1.2 square Main 0.0 2.8 solve Main 0.0 1.3 show_aVx Main 0.0 3.7 readsPrec_aYF Main 0.0 60.6 main Main 0.0 9.6 genNums Main 0.0 5.0 cell Main 0.0 1.2 individual inherited COST CENTRE MODULE no. entries %time %alloc %time %alloc MAIN MAIN 1 0 0.0 0.3 0.0 100.0 main Main 186 1 0.0 9.6 0.0 85.6 show_aVx Main 196 2 0.0 3.7 0.0 3.7 cell Main 197 16 0.0 0.0 0.0 0.0 solve Main 188 5 0.0 1.3 0.0 11.8 genNums Main 189 8 0.0 5.0 0.0 10.4 square Main 194 88 0.0 2.8 0.0 3.2 cell Main 195 16 0.0 0.4 0.0 0.4 col Main 192 4 0.0 0.7 0.0 1.1 cell Main 193 16 0.0 0.4 0.0 0.4 row Main 190 4 0.0 0.7 0.0 1.1 cell Main 191 16 0.0 0.4 0.0 0.4 readsPrec_aYF Main 187 3 0.0 60.6 0.0 60.6 CAF GHC.Read 151 1 0.0 1.2 0.0 1.2 CAF Text.Read.Lex 144 8 0.0 2.1 0.0 2.1 CAF GHC.Handle 128 4 0.0 10.7 0.0 10.7 CAF GHC.Conc 127 1 0.0 0.0 0.0 0.0 Does the column 'entries' represent the number of times the function was called? If so, I don't understand how the 'square' function could be called 88 times when it's caller is only called 8 times. Same thing with 'genNums' (called 8 times, and solve called 5 times) What am I missing here? Patrick -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada