benchpress-0.1: Test/BenchPress.hs
------------------------------------------------------------------------
-- |
-- Module : Test.BenchPress
-- Copyright : (c) Johan Tibell 2008
-- License : BSD3-style (see LICENSE)
--
-- Maintainer : johan.tibell@gmail.com
-- Stability : experimental
-- Portability : portable
--
-- Benchmarks actions and produces statistics such as min, mean,
-- median, standard deviation, and max execution time. Also computes
-- execution time percentiles. There are functions to pretty-print
-- the results.
--
-- Here's an example showing a benchmark of copying a file:
--
-- > import Control.Monad.Trans
-- > import qualified Data.ByteString as B
-- > import System.IO
-- > import Test.BenchPress
-- >
-- > inpath, outpath :: String
-- > inpath = "/tmp/infile"
-- > outpath = "/tmp/outfile"
-- >
-- > blockSize :: Int
-- > blockSize = 4 * 1024
-- >
-- > copyUsingByteString :: Handle -> Handle -> IO ()
-- > copyUsingByteString inf outf = go
-- > where
-- > go = do
-- > bs <- B.hGet inf blockSize
-- > let numRead = B.length bs
-- > if numRead > 0
-- > then B.hPut outf bs >> go
-- > else return ()
-- >
-- > main :: IO ()
-- > main = bench 100 $ liftIO $ do
-- > inf <- openBinaryFile inpath ReadMode
-- > outf <- openBinaryFile outpath WriteMode
-- > copyUsingByteString inf outf
-- > hClose outf
-- > hClose inf
--
------------------------------------------------------------------------
module Test.BenchPress
( -- * The 'Benchmark' type
Benchmark,
start,
stop,
-- * Running a benchmark
benchmark,
bench,
benchMany,
-- * Benchmark stats
Stats(..),
) where
import Control.Monad (forM_)
import Control.Monad.Trans (MonadIO, liftIO)
import Data.List (intercalate, sort)
import Data.Time.Clock (UTCTime, NominalDiffTime, diffUTCTime, getCurrentTime)
import qualified Math.Statistics as Math
import Prelude hiding (max, min)
import qualified Prelude
import Text.Printf (printf)
-- ---------------------------------------------------------------------
-- The Benchmark monad
-- | The benchmark state.
data S = S
{-# UNPACK #-} !NominalDiffTime -- elapsed time
{-# UNPACK #-} !(Maybe UTCTime) -- last mark
initState :: S
initState = S 0 Nothing
{-# INLINE initState #-}
-- | Starts the benchmark timer again after it has been previously
-- stopped by calling 'stop'. It's not necessary to call 'start' at
-- the beginning of the action you want to benchmark as it is done
-- automatically by 'benchmark'.
start :: Benchmark ()
start = Benchmark $ \(S elapsed _) -> do
mark <- liftIO getCurrentTime
return ((), S elapsed (Just mark))
{-# INLINE start #-}
-- | Stops the benchmark timer. Stopping the timer is useful when you
-- need to perform some set up that you don't want to count in the
-- benchmark timings. It's not necessary to call 'stop' at the end of
-- the action you want to benchmark as it is done automatically by
-- 'benchmark'.
stop :: Benchmark ()
stop = Benchmark $ \(S elapsed (Just mark)) -> do
now <- liftIO getCurrentTime
return ((), S (elapsed + (diffUTCTime now mark)) Nothing)
{-# INLINE stop #-}
newtype Benchmark a = Benchmark { runBenchmark :: S -> IO (a, S) }
execBenchmark :: Benchmark a -> S -> IO S
execBenchmark m s = do
(_, s') <- runBenchmark m s
return s'
instance Monad Benchmark where
return a = Benchmark $ \s -> return (a, s)
{-# INLINE return #-}
m >>= k = Benchmark $ \s -> do
(a, s') <- runBenchmark m s
runBenchmark (k a) s'
{-# INLINE (>>=) #-}
fail str = Benchmark $ \_ -> fail str
instance MonadIO Benchmark where
liftIO m = Benchmark $ \s -> m >>= \a -> return (a, s)
{-# INLINE liftIO #-}
-- ---------------------------------------------------------------------
-- Running a benchmark
-- TODO: Make sure that iters is > 0.
-- | @benchmark iters bm@ runs the action @bm@ @iters@ times measuring
-- the execution time of each run.
benchmark :: Int -> Benchmark a -> IO Stats
benchmark iters ma = do
timings <- (map millis) `fmap` go iters
let xs = sort timings
return Stats
{ min = head xs
, mean = Math.mean xs
, stddev = Math.stddev xs
, median = Math.median xs
, max = last xs
, percentiles = percentiles' xs
}
where
go 0 = return []
go n = do (S elapsed _) <- execBenchmark (start >> ma >> stop) initState
timings <- go $! n - 1
return $! elapsed : timings
-- | Convenience function that runs a benchmark using 'benchmark' and
-- prints timing statistics.
bench :: Int -> Benchmark a -> IO ()
bench iters bm = do
stats <- benchmark iters bm
let colWidth = columnWidth [stats]
printSummaryHeader 0 colWidth
printSummary colWidth "" stats
putStrLn ""
let psTbl = unlines $ columns (percentiles stats)
putStrLn "Percentiles (ms)"
putStr psTbl
where
columns = map $ \(p, value) -> printf " %3d%% %5.3f" p value
-- | Convenience function that runs several benchmarks using
-- 'benchmark' and prints a timing statistics summary. Each benchmark
-- has an associated label that is used to identify the benchmark in
-- the printed results.
benchMany :: Int -> [(String, Benchmark a)] -> IO ()
benchMany iters bms = do
results <- mapM (benchmark iters . snd) bms
let lblLen = maximum (map (length . fst) bms) + 2
colWidth = columnWidth results
printSummaryHeader lblLen colWidth
forM_ (zip (map fst bms) results) $ \(label, stats) ->
printSummary colWidth (printf "%-*s" lblLen (label ++ ": ")) stats
return ()
-- | Column headers.
headers :: [String]
headers = ["min", "mean", "+/-sd", "median", "max"]
-- | Computes the minimum column width needed to print the results
-- table.
columnWidth :: [Stats] -> Int
columnWidth = Prelude.max (maximum $ map length headers) . maximum . map width
where
width (Stats min' mean' sd median' max' _) =
maximum $ map (length . (printf "%.3f" :: Double -> String))
[min', mean', sd, median', max']
-- | Pad header with spaces up till desired width.
padHeader :: Int -> String -> String
padHeader w s
| n > w = s
| odd (w - n) = replicate (amt + 1) ' ' ++ s ++ replicate amt ' '
| otherwise = replicate amt ' ' ++ s ++ replicate amt ' '
where
n = length s
amt = (w - n) `div` 2
-- | Print table headers.
printSummaryHeader :: Int -> Int -> IO ()
printSummaryHeader lblLen colWidth = do
putStrLn "Times (ms)"
putStr $ (replicate lblLen ' ') ++ " "
putStrLn $ intercalate " " $ map (padHeader colWidth) headers
-- | Print a row showing a summary of the given stats.
printSummary :: Int -> String -> Stats -> IO ()
printSummary w label (Stats min' mean' sd median' max' _) =
putStrLn $ printf "%s %*.3f %*.3f %*.3f %*.3f %*.3f"
label w min' w mean' w sd w median' w max'
-- ---------------------------------------------------------------------
-- Benchmark stats
-- | Timing statistics for the benchmark. All measured times are
-- given in milliseconds.
data Stats = Stats
{ min :: Double
-- ^ Shortest execution time.
, mean :: Double
-- ^ Average execution time.
, stddev :: Double
-- ^ Execution time standard deviation.
, median :: Double
-- ^ Median execution time.
, max :: Double
-- ^ Longest execution time.
, percentiles :: [(Int, Double)]
-- ^ Execution time divided into percentiles. The first component
-- of the pair is the percentile given as an integer between 0 and
-- 100, inclusive. The second component is the execution time of
-- the slowest iteration within the percentile.
} deriving (Eq, Show)
-- ---------------------------------------------------------------------
-- Computing statistics
-- | Compute percentiles given a list of execution times in ascending
-- order.
percentiles' :: [Double] -> [(Int, Double)]
percentiles' xs = zipWith (\p ys -> (p, ys !! (rank p))) ps (repeat xs)
where
n = length xs
rank p = ceiling ((fromIntegral n / 100) * fromIntegral p :: Double) - 1
ps = [50, 66, 75, 80, 90, 95, 98, 99, 100]
-- ---------------------------------------------------------------------
-- Internal utilities
-- | Convert microseconds to milliseconds.
millis :: NominalDiffTime -> Double
millis t = realToFrac t * (10^(3 :: Int))