1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
{-# LANGUAGE Trustworthy #-}
-- |
-- Module : Criterion.Monad
-- Copyright : (c) 2009 Neil Brown
--
-- License : BSD-style
-- Maintainer : bos@serpentine.com
-- Stability : experimental
-- Portability : GHC
--
-- The environment in which most criterion code executes.
module Criterion.Monad
(
Criterion
, withConfig
, getGen
) where
import Control.Monad.Reader (asks, runReaderT)
import Control.Monad.Trans (liftIO)
import Criterion.Monad.Internal (Criterion(..), Crit(..))
import Criterion.Types hiding (measure)
import Data.IORef (IORef, newIORef, readIORef, writeIORef)
import System.IO.CodePage (withCP65001)
import System.Random.MWC (GenIO, createSystemRandom)
-- | Run a 'Criterion' action with the given 'Config'.
withConfig :: Config -> Criterion a -> IO a
withConfig cfg (Criterion act) = withCP65001 $ do
g <- newIORef Nothing
runReaderT act (Crit cfg g)
-- | Return a random number generator, creating one if necessary.
--
-- This is not currently thread-safe, but in a harmless way (we might
-- call 'createSystemRandom' more than once if multiple threads race).
getGen :: Criterion GenIO
getGen = memoise gen createSystemRandom
-- | Memoise the result of an 'IO' action.
--
-- This is not currently thread-safe, but hopefully in a harmless way.
-- We might call the given action more than once if multiple threads
-- race, so our caller's job is to write actions that can be run
-- multiple times safely.
memoise :: (Crit -> IORef (Maybe a)) -> IO a -> Criterion a
memoise ref generate = do
r <- Criterion $ asks ref
liftIO $ do
mv <- readIORef r
case mv of
Just rv -> return rv
Nothing -> do
rv <- generate
writeIORef r (Just rv)
return rv
|
