# Timing computations

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Revision as of 21:29, 28 February 2009 by DonStewart (Talk | contribs)

Timing an IO computation.

import Text.Printf import Control.Exception import System.CPUTime time :: IO t -> IO t time a = do start <- getCPUTime v <- a end <- getCPUTime let diff = (fromIntegral (end - start)) / (10^12) printf "Computation time: %0.3f sec\n" (diff :: Double) return v main = do putStrLn "Starting..." time $ product [1..10000] `seq` return () putStrLn "Done."

And running this.

$ runhaskell A.hs Starting... Computation time: 1.141 sec Done.

See also Timing out computations and Timing computation in cycles.

Timing a pure computation:

import Text.Printf import Control.Exception import System.CPUTime import Control.Parallel.Strategies import Control.Monad import System.Environment lim :: Int lim = 10^6 time :: (Num t, NFData t) => t -> IO () time y = do start <- getCPUTime replicateM_ lim $ do x <- evaluate $ 1 + y rnf x `seq` return () end <- getCPUTime let diff = (fromIntegral (end - start)) / (10^12) printf "Computation time: %0.9f sec\n" (diff :: Double) printf "Individual time: %0.9f sec\n" (diff / fromIntegral lim :: Double) return () main = do [n] <- getArgs let y = read n putStrLn "Starting..." time (y :: Int) putStrLn "Done."