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Timing computations

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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.