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1+{-# LANGUAGE BangPatterns #-}
2+
3+module Timer (timer) where
4+
5+import Control.Exception (evaluate)
6+import Data.Time.Clock.POSIX (getPOSIXTime)
7+import GHC.Float (FFFormat(..), formatRealFloat)
8+
9+ickyRound :: Int -> Double -> String
10+ickyRound k = formatRealFloat FFFixed (Just k)
11+
12+timer :: Int -> a -> (a -> b) -> IO String
13+timer count a0 f = do
14+ let loop !k !fastest
15+ | k <= 0 = return fastest
16+ | otherwise = do
17+ start <- getPOSIXTime
18+ let inner a i
19+ | i <= 0 = return ()
20+ | otherwise = evaluate (f a) >> inner a (i-1)
21+ inner a0 count
22+ end <- getPOSIXTime
23+ let elapsed = end - start
24+ loop (k-1) (min fastest (elapsed / fromIntegral count))
25+ t <- loop (3::Int) 1e300
26+ let log10 x = log x / log 10
27+ ft = realToFrac t
28+ prec = round (log10 (fromIntegral count) - log10 ft)
29+ return $! ickyRound prec ft
30+{-# NOINLINE timer #-}