{-# LANGUAGE BangPatterns               #-}
{-# LANGUAGE CPP                        #-}
{-# LANGUAGE DeriveDataTypeable         #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE ForeignFunctionInterface   #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MagicHash                  #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE TypeFamilies               #-}
#if __GLASGOW_HASKELL__ >= 801
{-# LANGUAGE TypeInType                 #-}
#endif
{-# LANGUAGE UnboxedTuples              #-}
#if __GLASGOW_HASKELL__ >= 707
{-# LANGUAGE RoleAnnotations            #-}
#endif
-- |
-- Module     : System.Random.PCG.Fast.Pure
-- Copyright  : Copyright (c) 2015, Christopher Chalmers <c.chalmers@me.com>
-- License    : BSD3
-- Maintainer : Christopher Chalmers <c.chalmers@me.com>
-- Stability  : experimental
-- Portability: CPP
--
-- Experimental pure haskell version of the fast variant of the PCG
-- random number generator. This module can perform faster than the c
-- bindings version, especially for parallel code.
--
-- See <http://www.pcg-random.org> for details.
--
-- @
-- import Control.Monad.ST
-- import System.Random.PCG.Fast.Pure
--
-- three :: [Double]
-- three = runST $ do
--   g <- create
--   a <- uniform g
--   b <- uniform g
--   c <- uniform g
--   return [a,b,c]
-- @
module System.Random.PCG.Fast.Pure
  ( -- * Gen
    Gen, GenIO, GenST
  , create, createSystemRandom, initialize, withSystemRandom

    -- * Getting random numbers
  , Variate (..)
  , advance, retract

    -- * Seeds
  , FrozenGen, save, restore, seed, initFrozen

    -- * Type restricted versions
    -- ** uniform
  , uniformW8, uniformW16, uniformW32, uniformW64
  , uniformI8, uniformI16, uniformI32, uniformI64
  , uniformF, uniformD, uniformBool

    -- ** uniformR
  , uniformRW8, uniformRW16, uniformRW32, uniformRW64
  , uniformRI8, uniformRI16, uniformRI32, uniformRI64
  , uniformRF, uniformRD, uniformRBool

    -- ** uniformB
  , uniformBW8, uniformBW16, uniformBW32, uniformBW64
  , uniformBI8, uniformBI16, uniformBI32, uniformBI64
  , uniformBF, uniformBD, uniformBBool
  ) where

import Control.Monad.Primitive
import Data.Bits
import Data.Data
import Data.Primitive.ByteArray
import Data.Primitive.Types
import GHC.Generics
import GHC.Word

import System.Random
import System.Random.PCG.Class

newtype FrozenGen = F Word64
  deriving (Int -> FrozenGen -> ShowS
[FrozenGen] -> ShowS
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Generic)

-- | State of the random number generator.
newtype Gen s = G (MutableByteArray s)
  deriving Typeable

type GenIO = Gen RealWorld
type GenST = Gen

-- $setup
-- >>> import System.Random.PCG.Fast.Pure as Fast.Pure
-- >>> import Control.Monad

-- internals -----------------------------------------------------------

data Pair = P {-# UNPACK #-} !Word64 {-# UNPACK #-} !Word32
  deriving Int -> Pair -> ShowS
[Pair] -> ShowS
Pair -> String
(Int -> Pair -> ShowS)
-> (Pair -> String) -> ([Pair] -> ShowS) -> Show Pair
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showsPrec :: Int -> Pair -> ShowS
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Show

fastMultiplier :: Word64
fastMultiplier :: Word64
fastMultiplier = Word64
6364136223846793005

-- Compute the next state of the generator
state :: Word64 -> Word64
state :: Word64 -> Word64
state Word64
s = Word64
s Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
* Word64
fastMultiplier

-- Compute the output random number from the state of the generator.
output :: Word64 -> Word32
output :: Word64 -> Word32
output Word64
s = Word64 -> Word32
forall a b. (Integral a, Num b) => a -> b
fromIntegral (Word64 -> Word32) -> Word64 -> Word32
forall a b. (a -> b) -> a -> b
$
  ((Word64
s Word64 -> Int -> Word64
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`shiftR` Int
22) Word64 -> Word64 -> Word64
forall a. Bits a => a -> a -> a
`xor` Word64
s) Word64 -> Int -> Word64
forall a. Bits a => a -> Int -> a
`unsafeShiftR` (Word64 -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral (Word64
s Word64 -> Int -> Word64
forall a. Bits a => a -> Int -> a
`shiftR` Int
61) Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
22)

-- Compute the next state and output in a strict pair.
pair :: Word64 -> Pair
pair :: Word64 -> Pair
pair Word64
s = Word64 -> Word32 -> Pair
P (Word64 -> Word64
state Word64
s) (Word64 -> Word32
output Word64
s)

-- Given some bound and the generator, compute the new state and bounded
-- random number.
bounded :: Word32 -> Word64 -> Pair
bounded :: Word32 -> Word64 -> Pair
bounded Word32
b Word64
s0 = Word64 -> Pair
go Word64
s0
  where
    t :: Word32
t = Word32 -> Word32
forall a. Num a => a -> a
negate Word32
b Word32 -> Word32 -> Word32
forall a. Integral a => a -> a -> a
`mod` Word32
b
    go :: Word64 -> Pair
go !Word64
s | Word32
r Word32 -> Word32 -> Bool
forall a. Ord a => a -> a -> Bool
>= Word32
t    = Word64 -> Word32 -> Pair
P Word64
s' (Word32
r Word32 -> Word32 -> Word32
forall a. Integral a => a -> a -> a
`mod` Word32
b)
          | Bool
otherwise = Word64 -> Pair
go Word64
s'
      where P Word64
s' Word32
r = Word64 -> Pair
pair Word64
s
{-# INLINE bounded #-}

advancing
  :: Word64 -- amount to advance by
  -> Word64 -- state
  -> Word64 -- multiplier
  -> Word64 -- increment
  -> Word64 -- new state
advancing :: Word64 -> Word64 -> Word64 -> Word64 -> Word64
advancing Word64
d0 Word64
s Word64
m0 Word64
p0 = Word64 -> Word64 -> Word64 -> Word64 -> Word64 -> Word64
go Word64
d0 Word64
m0 Word64
p0 Word64
1 Word64
0
  where
    go :: Word64 -> Word64 -> Word64 -> Word64 -> Word64 -> Word64
go Word64
d Word64
cm Word64
cp Word64
am Word64
ap
      | Word64
d Word64 -> Word64 -> Bool
forall a. Ord a => a -> a -> Bool
<= Word64
0    = Word64
am Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
* Word64
s Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
+ Word64
ap
      | Word64 -> Bool
forall a. Integral a => a -> Bool
odd Word64
d     = Word64 -> Word64 -> Word64 -> Word64 -> Word64 -> Word64
go Word64
d' Word64
cm' Word64
cp' (Word64
am Word64 -> Word64 -> Word64
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* Word64
cm) (Word64
ap Word64 -> Word64 -> Word64
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* Word64
cm Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
+ Word64
cp)
      | Bool
otherwise = Word64 -> Word64 -> Word64 -> Word64 -> Word64 -> Word64
go Word64
d' Word64
cm' Word64
cp' Word64
am        Word64
ap
      where
        cm' :: Word64
cm' = Word64
cm Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
* Word64
cm
        cp' :: Word64
cp' = (Word64
cm Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
+ Word64
1) Word64 -> Word64 -> Word64
forall a. Num a => a -> a -> a
* Word64
cp
        d' :: Word64
d'  = Word64
d Word64 -> Word64 -> Word64
forall a. Integral a => a -> a -> a
`div` Word64
2

advanceFast :: Word64 -> FrozenGen -> FrozenGen
advanceFast :: Word64 -> FrozenGen -> FrozenGen
advanceFast Word64
d (F Word64
s) = Word64 -> FrozenGen
F (Word64 -> FrozenGen) -> Word64 -> FrozenGen
forall a b. (a -> b) -> a -> b
$ Word64 -> Word64 -> Word64 -> Word64 -> Word64
advancing Word64
d Word64
s Word64
fastMultiplier Word64
0

------------------------------------------------------------------------
-- Seed
------------------------------------------------------------------------

-- | Save the state of a 'Gen' in a 'Seed'.
save :: PrimMonad m => Gen (PrimState m) -> m FrozenGen
save :: Gen (PrimState m) -> m FrozenGen
save (G MutableByteArray (PrimState m)
a) = MutableByteArray (PrimState m) -> Int -> m FrozenGen
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> m a
readByteArray MutableByteArray (PrimState m)
a Int
0
{-# INLINE save #-}

-- | Restore a 'Gen' from a 'Seed'.
restore :: PrimMonad m => FrozenGen -> m (Gen (PrimState m))
restore :: FrozenGen -> m (Gen (PrimState m))
restore FrozenGen
f = do
  MutableByteArray (PrimState m)
a <- Int -> m (MutableByteArray (PrimState m))
forall (m :: * -> *).
PrimMonad m =>
Int -> m (MutableByteArray (PrimState m))
newByteArray Int
8
  MutableByteArray (PrimState m) -> Int -> FrozenGen -> m ()
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> a -> m ()
writeByteArray MutableByteArray (PrimState m)
a Int
0 FrozenGen
f
  Gen (PrimState m) -> m (Gen (PrimState m))
forall (m :: * -> *) a. Monad m => a -> m a
return (Gen (PrimState m) -> m (Gen (PrimState m)))
-> Gen (PrimState m) -> m (Gen (PrimState m))
forall a b. (a -> b) -> a -> b
$! MutableByteArray (PrimState m) -> Gen (PrimState m)
forall s. MutableByteArray s -> Gen s
G MutableByteArray (PrimState m)
a
{-# INLINE restore #-}

-- | Generate a new seed using single 'Word64'.
--
--   >>> Fast.Pure.initFrozen 0
--   F 1
initFrozen :: Word64 -> FrozenGen
initFrozen :: Word64 -> FrozenGen
initFrozen Word64
w = Word64 -> FrozenGen
F (Word64
w Word64 -> Word64 -> Word64
forall a. Bits a => a -> a -> a
.|. Word64
1)

-- | Standard initial seed.
seed :: FrozenGen
seed :: FrozenGen
seed = Word64 -> FrozenGen
F Word64
0xcafef00dd15ea5e5

-- | Create a 'Gen' from a fixed initial seed.
create :: PrimMonad m => m (Gen (PrimState m))
create :: m (Gen (PrimState m))
create = FrozenGen -> m (Gen (PrimState m))
forall (m :: * -> *).
PrimMonad m =>
FrozenGen -> m (Gen (PrimState m))
restore FrozenGen
seed

-- | Initialize a generator a single word.
--
--   >>> Fast.Pure.initialize 0 >>= Fast.Pure.save
--   F 1
initialize :: PrimMonad m => Word64 -> m (Gen (PrimState m))
initialize :: Word64 -> m (Gen (PrimState m))
initialize Word64
a = FrozenGen -> m (Gen (PrimState m))
forall (m :: * -> *).
PrimMonad m =>
FrozenGen -> m (Gen (PrimState m))
restore (Word64 -> FrozenGen
initFrozen Word64
a)

-- | Seed with system random number. (\"@\/dev\/urandom@\" on Unix-like
--   systems, time otherwise).
withSystemRandom :: (GenIO -> IO a) -> IO a
withSystemRandom :: (GenIO -> IO a) -> IO a
withSystemRandom GenIO -> IO a
f = do
  Word64
w <- IO Word64
sysRandom
  Word64 -> IO (Gen (PrimState IO))
forall (m :: * -> *).
PrimMonad m =>
Word64 -> m (Gen (PrimState m))
initialize Word64
w IO GenIO -> (GenIO -> IO a) -> IO a
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= GenIO -> IO a
f

-- | Seed a PRNG with data from the system's fast source of pseudo-random
-- numbers. All the caveats of 'withSystemRandom' apply here as well.
createSystemRandom :: IO GenIO
createSystemRandom :: IO GenIO
createSystemRandom = (GenIO -> IO GenIO) -> IO GenIO
forall a. (GenIO -> IO a) -> IO a
withSystemRandom (GenIO -> IO GenIO
forall (m :: * -> *) a. Monad m => a -> m a
return :: GenIO -> IO GenIO)

-- | Advance the given generator n steps in log(n) time. (Note that a
--   \"step\" is a single random 32-bit (or less) 'Variate'. Data types
--   such as 'Double' or 'Word64' require two \"steps\".)
--
--   >>> Fast.Pure.create >>= \g -> replicateM_ 1000 (uniformW32 g) >> uniformW32 g
--   3725702568
--   >>> Fast.Pure.create >>= \g -> replicateM_ 500 (uniformD g) >> uniformW32 g
--   3725702568
--   >>> Fast.Pure.create >>= \g -> Fast.Pure.advance 1000 g >> uniformW32 g
--   3725702568
advance :: PrimMonad m => Word64 -> Gen (PrimState m) -> m ()
advance :: Word64 -> Gen (PrimState m) -> m ()
advance Word64
u (G MutableByteArray (PrimState m)
a) = do
  FrozenGen
s <- MutableByteArray (PrimState m) -> Int -> m FrozenGen
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> m a
readByteArray MutableByteArray (PrimState m)
a Int
0
  let s' :: FrozenGen
s' = Word64 -> FrozenGen -> FrozenGen
advanceFast Word64
u FrozenGen
s
  MutableByteArray (PrimState m) -> Int -> FrozenGen -> m ()
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> a -> m ()
writeByteArray MutableByteArray (PrimState m)
a Int
0 FrozenGen
s'
{-# INLINE advance #-}

-- | Retract the given generator n steps in log(2^64-n) time. This
--   is just @advance (-n)@.
--
--   >>> Fast.Pure.create >>= \g -> replicateM 3 (uniformW32 g)
--   [2951688802,2698927131,361549788]
--   >>> Fast.Pure.create >>= \g -> Fast.Pure.retract 1 g >> replicateM 3 (uniformW32 g)
--   [954135925,2951688802,2698927131]
retract :: PrimMonad m => Word64 -> Gen (PrimState m) -> m ()
retract :: Word64 -> Gen (PrimState m) -> m ()
retract Word64
u Gen (PrimState m)
g = Word64 -> Gen (PrimState m) -> m ()
forall (m :: * -> *).
PrimMonad m =>
Word64 -> Gen (PrimState m) -> m ()
advance (-Word64
u) Gen (PrimState m)
g
{-# INLINE retract #-}

------------------------------------------------------------------------
-- Instances
------------------------------------------------------------------------

instance (PrimMonad m, s ~ PrimState m) => Generator (Gen s) m where
  uniform1 :: (Word32 -> a) -> Gen s -> m a
uniform1 Word32 -> a
f (G MutableByteArray s
a) = do
    Word64
s <- MutableByteArray (PrimState m) -> Int -> m Word64
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> m a
readByteArray MutableByteArray s
MutableByteArray (PrimState m)
a Int
0
    let P Word64
s' Word32
r = Word64 -> Pair
pair Word64
s
    MutableByteArray (PrimState m) -> Int -> Word64 -> m ()
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> a -> m ()
writeByteArray MutableByteArray s
MutableByteArray (PrimState m)
a Int
0 Word64
s'
    a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return (a -> m a) -> a -> m a
forall a b. (a -> b) -> a -> b
$! Word32 -> a
f Word32
r
  {-# INLINE uniform1 #-}

  uniform2 :: (Word32 -> Word32 -> a) -> Gen s -> m a
uniform2 Word32 -> Word32 -> a
f (G MutableByteArray s
a) = do
    Word64
s <- MutableByteArray (PrimState m) -> Int -> m Word64
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> m a
readByteArray MutableByteArray s
MutableByteArray (PrimState m)
a Int
0
    let s' :: Word64
s' = Word64 -> Word64
state Word64
s
    MutableByteArray (PrimState m) -> Int -> Word64 -> m ()
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> a -> m ()
writeByteArray MutableByteArray s
MutableByteArray (PrimState m)
a Int
0 (Word64 -> Word64
state Word64
s')
    a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return (a -> m a) -> a -> m a
forall a b. (a -> b) -> a -> b
$! Word32 -> Word32 -> a
f (Word64 -> Word32
output Word64
s) (Word64 -> Word32
output Word64
s')
  {-# INLINE uniform2 #-}

  uniform1B :: (Word32 -> a) -> Word32 -> Gen s -> m a
uniform1B Word32 -> a
f Word32
b (G MutableByteArray s
a) = do
    Word64
s <- MutableByteArray (PrimState m) -> Int -> m Word64
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> m a
readByteArray MutableByteArray s
MutableByteArray (PrimState m)
a Int
0
    let P Word64
s' Word32
r = Word32 -> Word64 -> Pair
bounded Word32
b Word64
s
    MutableByteArray (PrimState m) -> Int -> Word64 -> m ()
forall a (m :: * -> *).
(Prim a, PrimMonad m) =>
MutableByteArray (PrimState m) -> Int -> a -> m ()
writeByteArray MutableByteArray s
MutableByteArray (PrimState m)
a Int
0 Word64
s'
    a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return (a -> m a) -> a -> m a
forall a b. (a -> b) -> a -> b
$! Word32 -> a
f Word32
r
  {-# INLINE uniform1B #-}

instance RandomGen FrozenGen where
  next :: FrozenGen -> (Int, FrozenGen)
next (F Word64
s) = (Word32 -> Word32 -> Int
forall a. Integral a => Word32 -> Word32 -> a
wordsTo64Bit Word32
w1 Word32
w2, Word64 -> FrozenGen
F Word64
s'')
    where
      P Word64
s'  Word32
w1 = Word64 -> Pair
pair Word64
s
      P Word64
s'' Word32
w2 = Word64 -> Pair
pair Word64
s'
  {-# INLINE next #-}

  split :: FrozenGen -> (FrozenGen, FrozenGen)
split (F Word64
s) = (Word32 -> Word32 -> FrozenGen
mk Word32
w1 Word32
w2, Word32 -> Word32 -> FrozenGen
mk Word32
w3 Word32
w4)
    where
      mk :: Word32 -> Word32 -> FrozenGen
mk Word32
a Word32
b  = Word64 -> FrozenGen
initFrozen (Word64 -> FrozenGen) -> Word64 -> FrozenGen
forall a b. (a -> b) -> a -> b
$! Word32 -> Word32 -> Word64
forall a. Integral a => Word32 -> Word32 -> a
wordsTo64Bit Word32
a Word32
b
      P Word64
s1 Word32
w1 = Word64 -> Pair
pair Word64
s
      P Word64
s2 Word32
w2 = Word64 -> Pair
pair Word64
s1
      P Word64
s3 Word32
w3 = Word64 -> Pair
pair Word64
s2
      w4 :: Word32
w4 = Word64 -> Word32
output Word64
s3 -- abandon old state
  {-# INLINE split #-}