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-- |
-- Module: Math.NumberTheory.Primes.Sieve.Eratosthenes
-- Copyright: (c) 2011 Daniel Fischer
-- Licence: MIT
-- Maintainer: Daniel Fischer <daniel.is.fischer@googlemail.com>
--
-- Sieve
--
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# OPTIONS_GHC -fspec-constr-count=8 #-}
module Math.NumberTheory.Primes.Sieve.Eratosthenes
( primes
, psieveFrom
, PrimeSieve(..)
, psieveList
, primeList
, primeSieve
, sieveBits
, sieveRange
, sieveTo
) where
import Control.Monad (when)
import Control.Monad.ST
import Data.Array.Base
import Data.Array.ST
import Data.Bits
import Data.Coerce
import Data.Proxy
import Data.Word
import Math.NumberTheory.Primes.Sieve.Indexing
import Math.NumberTheory.Primes.Types
import Math.NumberTheory.Roots
import Math.NumberTheory.Utils.FromIntegral
iXMASK :: Num a => a
iXMASK = 0xFFFFF
iXBITS :: Int
iXBITS = 20
iXJMASK :: Num a => a
iXJMASK = 0x7FFFFF
iXJBITS :: Int
iXJBITS = 23
jMASK :: Int
jMASK = 7
jBITS :: Int
jBITS = 3
-- Sieve in 128K chunks.
-- Large enough to get something done per chunk
-- and hopefully small enough to fit in the cache.
sieveBytes :: Int
sieveBytes = 128 * 1024
-- Number of bits per chunk.
sieveBits :: Int
sieveBits = 8 * sieveBytes
-- Last index of chunk.
lastIndex :: Int
lastIndex = sieveBits - 1
-- Range of a chunk.
sieveRange :: Int
sieveRange = 30 * sieveBytes
wSHFT :: (Bits a, Num a) => a
wSHFT = if finiteBitSize (0 :: Word) == 64 then 6 else 5
-- | Compact store of primality flags.
data PrimeSieve = PS !Integer {-# UNPACK #-} !(UArray Int Bool)
-- | Sieve primes up to (and including) a bound (or 7, if bound is smaller).
-- For small enough bounds, this is more efficient than
-- using the segmented sieve.
--
-- Since arrays are 'Int'-indexed, overflow occurs when the sieve
-- size comes near @'maxBound' :: 'Int'@, that corresponds to an
-- upper bound near @15/8*'maxBound'@. On @32@-bit systems, that
-- is often within memory limits, so don't give bounds larger than
-- @8*10^9@ there.
primeSieve :: Integer -> PrimeSieve
primeSieve bound = PS 0 (runSTUArray $ sieveTo bound)
-- | Generate a list of primes for consumption from a
-- 'PrimeSieve'.
primeList :: forall a. Integral a => PrimeSieve -> [Prime a]
primeList ps@(PS v _)
| doesNotFit (Proxy :: Proxy a) v
= [] -- has an overflow already happened?
| v == 0 = (coerce :: [a] -> [Prime a])
$ takeWhileIncreasing $ 2 : 3 : 5 : primeListInternal ps
| otherwise = (coerce :: [a] -> [Prime a])
$ takeWhileIncreasing $ primeListInternal ps
primeListInternal :: Num a => PrimeSieve -> [a]
primeListInternal (PS v0 bs)
= map ((+ fromInteger v0) . toPrim)
$ filter (unsafeAt bs) [lo..hi]
where
(lo, hi) = bounds bs
-- | Returns true if integer is beyond representation range of type a.
doesNotFit :: forall a. Integral a => Proxy a -> Integer -> Bool
doesNotFit _ v = toInteger (fromInteger v :: a) /= v
-- | Extracts the longest strictly increasing prefix of the list
-- (possibly infinite).
takeWhileIncreasing :: Ord a => [a] -> [a]
takeWhileIncreasing = \case
[] -> []
x : xs -> x : foldr go (const []) xs x
where
go :: Ord a => a -> (a -> [a]) -> a -> [a]
go y f z = if z < y then y : f y else []
-- | Ascending list of primes.
--
-- >>> take 10 primes
-- [Prime 2,Prime 3,Prime 5,Prime 7,Prime 11,Prime 13,Prime 17,Prime 19,Prime 23,Prime 29]
--
-- 'primes' is a polymorphic list, so the results of computations are not retained in memory.
-- Make it monomorphic to take advantages of memoization. Compare
--
-- >>> primes !! 1000000 :: Prime Int -- (5.32 secs, 6,945,267,496 bytes)
-- Prime 15485867
-- >>> primes !! 1000000 :: Prime Int -- (5.19 secs, 6,945,267,496 bytes)
-- Prime 15485867
--
-- against
--
-- >>> let primes' = primes :: [Prime Int]
-- >>> primes' !! 1000000 :: Prime Int -- (5.29 secs, 6,945,269,856 bytes)
-- Prime 15485867
-- >>> primes' !! 1000000 :: Prime Int -- (0.02 secs, 336,232 bytes)
-- Prime 15485867
primes :: Integral a => [Prime a]
primes
= (coerce :: [a] -> [Prime a])
$ takeWhileIncreasing $ 2 : 3 : 5 : concatMap primeListInternal psieveList
-- | List of primes in the form of a list of 'PrimeSieve's, more compact than
-- 'primes', thus it may be better to use @'psieveList' >>= 'primeList'@
-- than keeping the list of primes alive during the entire run.
psieveList :: [PrimeSieve]
psieveList = makeSieves plim sqlim 0 0 cache
where
plim = 4801 -- prime #647, 644 of them to use
sqlim = plim*plim
cache = runSTUArray $ do
sieve <- sieveTo (4801 :: Integer)
new <- unsafeNewArray_ (0,1287) :: ST s (STUArray s Int Word64)
let fill j indx
| 1279 < indx = return new -- index of 4801 = 159*30 + 31 ~> 159*8+7
| otherwise = do
p <- unsafeRead sieve indx
if p
then do
let !i = indx .&. jMASK
k = indx `shiftR` jBITS
strt1 = (k*(30*k + 2*rho i) + byte i) `shiftL` jBITS + idx i
!strt = intToWord64 (strt1 .&. iXMASK)
!skip = intToWord64 (strt1 `shiftR` iXBITS)
!ixes = intToWord64 indx `shiftL` iXJBITS + strt `shiftL` jBITS + intToWord64 i
unsafeWrite new j skip
unsafeWrite new (j+1) ixes
fill (j+2) (indx+1)
else fill j (indx+1)
fill 0 0
makeSieves :: Integer -> Integer -> Integer -> Integer -> UArray Int Word64 -> [PrimeSieve]
makeSieves plim sqlim bitOff valOff cache
| valOff' < sqlim =
let (nc, bs) = runST $ do
cch <- unsafeThaw cache :: ST s (STUArray s Int Word64)
bs0 <- slice cch
fcch <- unsafeFreeze cch
fbs0 <- unsafeFreeze bs0
return (fcch, fbs0)
in PS valOff bs : makeSieves plim sqlim bitOff' valOff' nc
| otherwise =
let plim' = plim + 4800
sqlim' = plim' * plim'
(nc,bs) = runST $ do
cch <- growCache bitOff plim cache
bs0 <- slice cch
fcch <- unsafeFreeze cch
fbs0 <- unsafeFreeze bs0
return (fcch, fbs0)
in PS valOff bs : makeSieves plim' sqlim' bitOff' valOff' nc
where
valOff' = valOff + intToInteger sieveRange
bitOff' = bitOff + intToInteger sieveBits
slice :: STUArray s Int Word64 -> ST s (STUArray s Int Bool)
slice cache = do
hi <- snd `fmap` getBounds cache
sieve <- newArray (0,lastIndex) True
let treat pr
| hi < pr = return sieve
| otherwise = do
w <- unsafeRead cache pr
if w /= 0
then unsafeWrite cache pr (w-1)
else do
ixes <- unsafeRead cache (pr+1)
let !stj = word64ToInt ixes .&. iXJMASK -- position of multiple and index of cofactor
!ixw = word64ToInt (ixes `shiftR` iXJBITS) -- prime data, up to 41 bits
!i = ixw .&. jMASK
!k = ixw - i -- On 32-bits, k > 44717396 means overflow is possible in tick
!o = i `shiftL` jBITS
!j = stj .&. jMASK -- index of cofactor
!s = stj `shiftR` jBITS -- index of first multiple to tick off
(n, u) <- tick k o j s
let !skip = intToWord64 (n `shiftR` iXBITS)
!strt = intToWord64 (n .&. iXMASK)
unsafeWrite cache pr skip
unsafeWrite cache (pr+1) ((ixes .&. complement iXJMASK) .|. strt `shiftL` jBITS .|. intToWord64 u)
treat (pr+2)
tick stp off j ix
| lastIndex < ix = return (ix - sieveBits, j)
| otherwise = do
p <- unsafeRead sieve ix
when p (unsafeWrite sieve ix False)
tick stp off ((j+1) .&. jMASK) (ix + stp*delta j + tau (off+j))
treat 0
-- | Sieve up to bound in one go.
sieveTo :: Integer -> ST s (STUArray s Int Bool)
sieveTo bound = arr
where
(bytes,lidx) = idxPr bound
!mxidx = 8*bytes+lidx
mxval :: Integer
mxval = 30*intToInteger bytes + intToInteger (rho lidx)
!mxsve = integerSquareRoot mxval
(kr,r) = idxPr mxsve
!svbd = 8*kr+r
arr = do
ar <- newArray (0,mxidx) True
let start k i = 8*(k*(30*k+2*rho i) + byte i) + idx i
tick stp off j ix
| mxidx < ix = return ()
| otherwise = do
p <- unsafeRead ar ix
when p (unsafeWrite ar ix False)
tick stp off ((j+1) .&. jMASK) (ix + stp*delta j + tau (off+j))
sift ix
| svbd < ix = return ar
| otherwise = do
p <- unsafeRead ar ix
when p (do let i = ix .&. jMASK
k = ix `shiftR` jBITS
!off = i `shiftL` jBITS
!stp = ix - i
tick stp off i (start k i))
sift (ix+1)
sift 0
growCache :: Integer -> Integer -> UArray Int Word64 -> ST s (STUArray s Int Word64)
growCache offset plim old = do
let (_,num) = bounds old
(bt,ix) = idxPr plim
!start = 8*bt+ix+1
!nlim = plim+4800
sieve <- sieveTo nlim -- Implement SieveFromTo for this, it's pretty wasteful when nlim isn't
(_,hi) <- getBounds sieve -- very small anymore
more <- countFromToWd start hi sieve
new <- unsafeNewArray_ (0,num+2*more) :: ST s (STUArray s Int Word64)
let copy i
| num < i = return ()
| otherwise = do
unsafeWrite new i (old `unsafeAt` i)
copy (i+1)
copy 0
let fill j indx
| hi < indx = return new
| otherwise = do
p <- unsafeRead sieve indx
if p
then do
let !i = indx .&. jMASK
k :: Integer
k = intToInteger (indx `shiftR` jBITS)
strt0 = ((k*(30*k + intToInteger (2*rho i))
+ intToInteger (byte i)) `shiftL` jBITS)
+ intToInteger (idx i)
strt1 = strt0 - offset
!strt = integerToWord64 strt1 .&. iXMASK
!skip = integerToWord64 (strt1 `shiftR` iXBITS)
!ixes = intToWord64 indx `shiftL` iXJBITS .|. strt `shiftL` jBITS .|. intToWord64 i
unsafeWrite new j skip
unsafeWrite new (j+1) ixes
fill (j+2) (indx+1)
else fill j (indx+1)
fill (num+1) start
-- Danger: relies on start and end being the first resp. last
-- index in a Word
-- Do not use except in growCache and psieveFrom
{-# INLINE countFromToWd #-}
countFromToWd :: Int -> Int -> STUArray s Int Bool -> ST s Int
countFromToWd start end ba = do
wa <- (castSTUArray :: STUArray s Int Bool -> ST s (STUArray s Int Word)) ba
let !sb = start `shiftR` wSHFT
!eb = end `shiftR` wSHFT
count !acc i
| eb < i = return acc
| otherwise = do
w <- unsafeRead wa i
count (acc + popCount w) (i+1)
count 0 sb
-- | @'psieveFrom' n@ creates the list of 'PrimeSieve's starting roughly
-- at @n@. Due to the organisation of the sieve, the list may contain
-- a few primes less than @n@.
-- This form uses less memory than @['Integer']@, hence it may be preferable
-- to use this if it is to be reused.
psieveFrom :: Integer -> [PrimeSieve]
psieveFrom n = makeSieves plim sqlim bitOff valOff cache
where
k0 = ((n `max` 7) - 7) `quot` 30 -- beware arithmetic underflow
valOff = 30*k0
bitOff = 8*k0
start = valOff+7
ssr = integerSquareRoot (start-1) + 1
end1 = start - 6 + intToInteger sieveRange
plim0 = integerSquareRoot end1
plim = plim0 + 4801 - (plim0 `rem` 4800)
sqlim = plim*plim
cache = runSTUArray $ do
sieve <- sieveTo plim
(lo,hi) <- getBounds sieve
pct <- countFromToWd lo hi sieve
new <- unsafeNewArray_ (0,2*pct-1) :: ST s (STUArray s Int Word64)
let fill j indx
| hi < indx = return new
| otherwise = do
isPr <- unsafeRead sieve indx
if isPr
then do
let !i = indx .&. jMASK
!moff = i `shiftL` jBITS
k :: Integer
k = intToInteger (indx `shiftR` jBITS)
p = 30*k+intToInteger (rho i)
q0 = (start-1) `quot` p
(skp0,q1) = q0 `quotRem` intToInteger sieveRange
(b0,r0)
| q1 == 0 = (-1,6)
| q1 < 7 = (-1,7)
| otherwise = idxPr (integerToInt q1 :: Int)
(b1,r1) | r0 == 7 = (b0+1,0)
| otherwise = (b0,r0+1)
b2 = skp0*intToInteger sieveBytes + intToInteger b1
strt0 = ((k*(30*b2 + intToInteger (rho r1))
+ b2 * intToInteger (rho i)
+ intToInteger (mu (moff + r1))) `shiftL` jBITS)
+ intToInteger (nu (moff + r1))
strt1 = ((k*(30*k + intToInteger (2*rho i))
+ intToInteger (byte i)) `shiftL` jBITS)
+ intToInteger (idx i)
(strt2,r2)
| p < ssr = (strt0 - bitOff,r1)
| otherwise = (strt1 - bitOff, i)
!strt = integerToWord64 strt2 .&. iXMASK
!skip = integerToWord64 (strt2 `shiftR` iXBITS)
!ixes = intToWord64 indx `shiftL` iXJBITS .|. strt `shiftL` jBITS .|. intToWord64 r2
unsafeWrite new j skip
unsafeWrite new (j+1) ixes
fill (j+2) (indx+1)
else fill j (indx+1)
fill 0 0
{-# INLINE delta #-}
delta :: Int -> Int
delta = unsafeAt deltas
deltas :: UArray Int Int
deltas = listArray (0,7) [4,2,4,2,4,6,2,6]
{-# INLINE tau #-}
tau :: Int -> Int
tau = unsafeAt taus
taus :: UArray Int Int
taus = listArray (0,63)
[ 7, 4, 7, 4, 7, 12, 3, 12
, 12, 6, 11, 6, 12, 18, 5, 18
, 14, 7, 13, 7, 14, 21, 7, 21
, 18, 9, 19, 9, 18, 27, 9, 27
, 20, 10, 21, 10, 20, 30, 11, 30
, 25, 12, 25, 12, 25, 36, 13, 36
, 31, 15, 31, 15, 31, 47, 15, 47
, 33, 17, 33, 17, 33, 49, 17, 49
]
{-# INLINE byte #-}
byte :: Int -> Int
byte = unsafeAt startByte
startByte :: UArray Int Int
startByte = listArray (0,7) [1,3,5,9,11,17,27,31]
{-# INLINE idx #-}
idx :: Int -> Int
idx = unsafeAt startIdx
startIdx :: UArray Int Int
startIdx = listArray (0,7) [4,7,4,4,7,4,7,7]
{-# INLINE mu #-}
mu :: Int -> Int
mu = unsafeAt mArr
{-# INLINE nu #-}
nu :: Int -> Int
nu = unsafeAt nArr
mArr :: UArray Int Int
mArr = listArray (0,63)
[ 1, 2, 2, 3, 4, 5, 6, 7
, 2, 3, 4, 6, 6, 8, 10, 11
, 2, 4, 5, 7, 8, 9, 12, 13
, 3, 6, 7, 9, 10, 12, 16, 17
, 4, 6, 8, 10, 11, 14, 18, 19
, 5, 8, 9, 12, 14, 17, 22, 23
, 6, 10, 12, 16, 18, 22, 27, 29
, 7, 11, 13, 17, 19, 23, 29, 31
]
nArr :: UArray Int Int
nArr = listArray (0,63)
[ 4, 3, 7, 6, 2, 1, 5, 0
, 3, 7, 5, 0, 6, 2, 4, 1
, 7, 5, 4, 1, 0, 6, 3, 2
, 6, 0, 1, 4, 5, 7, 2, 3
, 2, 6, 0, 5, 7, 3, 1, 4
, 1, 2, 6, 7, 3, 4, 0, 5
, 5, 4, 3, 2, 1, 0, 7, 6
, 0, 1, 2, 3, 4, 5, 6, 7
]
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