On Wed, May 27, 2009 at 9:59 AM, Andrew Butterfield
Magnus Therning wrote:
timeIt times ioa = let timeOnce = do t1 <- getCPUTime a <- ioa t2 <- getCPUTime let t = fromIntegral (t2-t1) * 1e-12 return t in sequence $ take times $ repeat timeOnce
main = do fh <- openBinaryFile "/dev/urandom" ReadMode d <- liftM BS.unpack $ BS.hGet fh 100000 t <- timeIt 10 $ return $! B64.encode d print t
I suspect that it all comes from `B64.encode d` being pure, hence the encoding happens only once. Now I _really_ want the encoding to happen 10 times, is there some easy way to achieve this?
A quick answer - not a lot of thought - pass function *and* argument separately into timeIt ?
timeIt times ioaf ioaarg .... a <- ioaf ioaarg
As it stands you pass the thunk (B64.encode d) in so it only gets evaluated once If you pass the function and argument in then a new thunk is built each time around (unless the optimiser nabbles it.......)
Hmm, my naive implementation of that didn't improve the situation, `t <- timeIt 10 (\ x -> return $! B64.encode x) d` still results in only one measurement /= 0. Of course that also makes `timeIt` less general. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe