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|
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE LambdaCase #-}
module PPL.Internal
( uniform,
Prob (..),
Meas,
score,
scoreLog,
sample,
samples,
newTree,
HashMap,
Tree(..),
)
where
import Control.Monad
import Control.Monad.IO.Class
import Control.Monad.Trans.Class
import Control.Monad.Trans.Writer
import Data.Bifunctor
import Data.Monoid
import qualified Language.Haskell.TH.Syntax as TH
import Numeric.Log
import System.Random hiding (split, uniform)
import qualified System.Random as R
import Data.IORef
import System.IO.Unsafe
import qualified Data.Vector.Mutable as VM
import qualified Data.Vector.Unboxed.Mutable as UM
import qualified Data.Vector.Hashtables as H
type HashMap k v = H.Dictionary (H.PrimState IO) VM.MVector k UM.MVector v
-- Reimplementation of the LazyPPL monads to avoid some dependencies
data Tree = Tree
{ draw :: !Double,
split :: (Tree, Tree)
}
{-# INLINE newTree #-}
newTree :: IORef (HashMap [Bool] Double, StdGen) -> Tree
newTree s = go []
where
go id = Tree (unsafePerformIO $ do
(m, g) <- readIORef s
H.lookup m id >>= \case
Nothing -> do
let (x, g') = R.random g
H.insert m id x
writeIORef s (m, g')
pure x
Just x -> pure x) (go (False : id), go (True : id))
newtype Prob a = Prob {runProb :: Tree -> a}
instance Monad Prob where
Prob f >>= g = Prob $ \t ->
let (t1, t2) = split t
(Prob g') = g (f t1)
in g' t2
instance Functor Prob where fmap = liftM
instance Applicative Prob where pure = Prob . const; (<*>) = ap
uniform = Prob $ \(Tree r _) -> r
newtype Meas a = Meas (WriterT (Product (Log Double)) Prob a)
deriving (Functor, Applicative, Monad)
{-# INLINE score #-}
score :: Double -> Meas ()
score = scoreLog . Exp . log . max eps
where
eps = $(TH.lift (2 * until ((== 1) . (1 +)) (/ 2) (1 :: Double))) -- machine epsilon, force compile time eval
{-# INLINE scoreLog #-}
scoreLog :: Log Double -> Meas ()
scoreLog = Meas . tell . Product
{-# INLINE sample #-}
sample :: Prob a -> Meas a
sample = Meas . lift
{-# INLINE samples #-}
samples :: forall a. Meas a -> Tree -> [(a, Log Double)]
samples (Meas m) = map (second getProduct) . runProb f
where
f = runWriterT m >>= \x -> (x :) <$> f
|
