module Control.Monad.MC.Sample (
sample,
sampleWithWeights,
sampleSubset,
sampleSubset',
sampleInt,
sampleIntWithWeights,
sampleIntSubset,
sampleIntSubset',
shuffle,
shuffleInt,
shuffleInt',
) where
import Control.Monad
import Control.Monad.ST
import Control.Monad.MC.Base
import Control.Monad.MC.Walker
import Data.Vector.Unboxed( MVector, Unbox )
import qualified Data.Vector as BV
import qualified Data.Vector.Mutable as BMV
import qualified Data.Vector.Unboxed as V
import qualified Data.Vector.Generic.Mutable as MV
sample :: (MonadMC m) => [a] -> m a
sample xs = let
n = length xs
in sampleHelp n xs $ sampleInt n
sampleWithWeights :: (MonadMC m) => [(Double, a)] -> m a
sampleWithWeights wxs = let
(ws,xs) = unzip wxs
n = length xs
in sampleHelp n xs $ sampleIntWithWeights ws n
sampleSubset :: (MonadMC m) => Int -> [a] -> m [a]
sampleSubset k xs = let
n = length xs
in sampleListHelp n xs $ sampleIntSubset k n
sampleSubset' :: (MonadMC m) => Int -> [a] -> m [a]
sampleSubset' k xs = do
s <- sampleSubset k xs
length s `seq` return s
sampleHelp :: (Monad m) => Int -> [a] -> m Int -> m a
sampleHelp _n xs f = let
arr = BV.fromList xs
in liftM (BV.unsafeIndex arr) f
sampleHelpU :: (Unbox a, Monad m) => Int -> [a] -> m Int -> m a
sampleHelpU _n xs f = let
arr = V.fromList xs
in liftM (V.unsafeIndex arr) f
sampleListHelp :: (Monad m) => Int -> [a] -> m [Int] -> m [a]
sampleListHelp _n xs f = let
arr = BV.fromList xs
in liftM (map $ BV.unsafeIndex arr) f
sampleListHelpU :: (Unbox a, Monad m) => Int -> [a] -> m [Int] -> m [a]
sampleListHelpU _n xs f = let
arr = V.fromList xs
in liftM (map $ V.unsafeIndex arr) f
sampleInt :: (MonadMC m) => Int -> m Int
sampleInt n | n < 1 = fail "invalid argument"
| otherwise = uniformInt n
sampleIntWithWeights :: (MonadMC m) => [Double] -> Int -> m Int
sampleIntWithWeights ws n =
let qjs = computeTable n ws
in liftM (indexTable qjs) (uniform 0 1)
sampleIntSubset :: (MonadMC m) => Int -> Int -> m [Int]
sampleIntSubset k n | k < 0 = fail "negative subset size"
| k > n = fail "subset size is too big"
| otherwise = do
us <- randomIndices k n
return $ runST $ do
ints <- MV.new n :: ST s (MVector s Int)
sequence_ [ MV.unsafeWrite ints i i | i <- [0 .. n1] ]
sampleIntSubsetHelp ints us (n1)
where
randomIndices k' n' | k' == 0 = return []
| otherwise = unsafeInterleaveMC $ do
u <- uniformInt n'
us <- randomIndices (k'1) (n'1)
return (u:us)
sampleIntSubsetHelp _ [] _ = return []
sampleIntSubsetHelp ints (u:us) n' = unsafeInterleaveST $ do
i <- MV.unsafeRead ints u
MV.unsafeWrite ints u =<< MV.unsafeRead ints n'
is <- sampleIntSubsetHelp ints us (n'1)
return (i:is)
sampleIntSubset' :: (MonadMC m) => Int -> Int -> m [Int]
sampleIntSubset' k n = do
s <- sampleIntSubset k n
length s `seq` return s
shuffle :: (MonadMC m) => [a] -> m [a]
shuffle xs = let
n = length xs
in shuffleInt n >>= \swaps -> (return . BV.toList . BV.create) $ do
marr <- MV.new n :: ST s (BMV.MVector s a)
zipWithM_ (MV.unsafeWrite marr) [0 .. n1] xs
mapM_ (swap marr) swaps
return marr
where
swap marr (i,j) | i == j = return ()
| otherwise = do
x <- MV.unsafeRead marr i
y <- MV.unsafeRead marr j
MV.unsafeWrite marr i y
MV.unsafeWrite marr j x
shuffleU :: (Unbox a, MonadMC m) => [a] -> m [a]
shuffleU xs = let
n = length xs
in shuffleInt n >>= \swaps -> (return . V.toList . V.create) $ do
marr <- MV.new n
zipWithM_ (MV.unsafeWrite marr) [0 .. n1] xs
mapM_ (swap marr) swaps
return marr
where
swap marr (i,j) | i == j = return ()
| otherwise = do
x <- MV.unsafeRead marr i
y <- MV.unsafeRead marr j
MV.unsafeWrite marr i y
MV.unsafeWrite marr j x
shuffleInt :: (MonadMC m) => Int -> m [(Int,Int)]
shuffleInt n =
let shuffleIntHelp i | i <= 1 = return []
| otherwise = unsafeInterleaveMC $ do
j <- uniformInt i
ijs <- shuffleIntHelp (i1)
return $ (i1,j):ijs in
shuffleIntHelp n
shuffleInt' :: (MonadMC m) => Int -> m [(Int,Int)]
shuffleInt' n = do
ss <- shuffleInt n
length ss `seq` return ss