Timing Functions

[Lemmih]

On Mon, 17 Jan 2005 10:48:18 -0600, jekwtw <jeaniek7 at comcast.net> wrote:
>  
> I'm putting together a script to gather run-time stats for some functions
> I'm working with, and I'm having a terrible time.  My strategy is to
> evaluate a function a number of times and compute the difference between the
> elapsed CPU time before and after the repeated calls. 
> 
> > timeNReps :: (a -> b) -> a -> Int -> FilePath -> IO ()
> > timeNReps func arg reps fileName =
> >             do t0 <- System.CPUTime.getCPUTime
> >                  runNReps func arg reps
> >                  t1 <- System.CPUTime.getCPUTime
> >                  appendFile fileName ((showMS (t1 - t0)) ++ "\n")
> >    where
> >    showMS n = show (n `quot` 1000000000)
> 
> showMS just converts the pico-second result into milli-seconds and
> stringifies it.
> 
> runNReps is an IO program (do sequence) that is intended to call the
> function and tail-call itself a given number of times: 
>   
> > runNReps :: (Int -> a) -> Int -> Int -> IO ()
> > runNReps f x todo
> >             | todo > 0 = do let junk = (f x)
> >                                    runNReps f x (todo - 1)
> >             | otherwise = return (())

Haskell is a non-strict language which means that 'junk' wont be
evaluated since it's not necessary for the function to terminate.
Check 'replicateM_' from Control.Monad.
> runNReps :: Int -> IO a -> IO ()
> runNReps = replicateM_

-- 
Friendly,
  Lemmih