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import GHC.Conc
import Control.Parallel
import Control.Parallel.Strategies
import System.Environment
import System.IO
import Control.Monad
import Text.Printf
import Data.Time.Clock
main = do
[n,q,t] <- fmap (fmap read) getArgs
forkIO $ do
forM_ (cycle ([n,n-1..1] ++ [2..n-1])) $ \m -> do
setNumCapabilities m
threadDelay t
printf "%d" (nqueens q)
nqueens :: Int -> Int
nqueens nq = length (pargen 0 [])
where
safe :: Int -> Int -> [Int] -> Bool
safe x d [] = True
safe x d (q:l) = x /= q && x /= q+d && x /= q-d && safe x (d+1) l
gen :: [[Int]] -> [[Int]]
gen bs = [ (q:b) | b <- bs, q <- [1..nq], safe q 1 b ]
pargen :: Int -> [Int] -> [[Int]]
pargen n b
| n >= threshold = iterate gen [b] !! (nq - n)
| otherwise = concat bs
where bs = map (pargen (n+1)) (gen [b]) `using` parList rdeepseq
threshold = 3
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