Split the Sudoku solver module into Board and Solver
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{-
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A solution to rubyquiz 43 (http://rubyquiz.com/quiz43.html).
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A fast multi-threaded Sudoku solver using recursive depth-first backtracking
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for searching and constraint propagation for solving.
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Solves the 49191 puzzles at http://school.maths.uwa.edu.au/~gordon/sudoku17
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in 32 seconds on a quad core machine with output switched off.
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Each puzzle should be formatted as a single line of 81 character, top to bottom,
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left to right, with digits 1 to 9 if the cell has a value else a dot (.).
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Example:
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4.....8.5.3..........7......2.....6.....8.4......1.......6.3.7.5..2.....1.4......
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Usage:
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cat sudoku17 | bin/SudokuSolver +RTS -N4 -H800m -K50m
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echo "4.....8.5.3..........7......2.....6.....8.4......1.......6.3.7.5..2.....1.4......" | bin/SudokuSolver
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Copyright 2012 Abhinav Sarkar <abhinav@abhinavsarkar.net>
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-}
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{-# LANGUAGE BangPatterns, RecordWildCards #-}
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module SudokuSolver (Cell(..), Board, emptyBoard, boardCells, cellValues,
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isBoardSolved, readBoard, showBoard, prettyShowBoard,
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solveSudoku, main)
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module Sudoku.Board (Cell(..), Board(..), emptyBoard, boardCells, cellValues,
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firstSol, updateBoard, constrainBoard,
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isBoardSolved, readBoard, showBoard, prettyShowBoard)
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where
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import qualified Data.Set as S
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import qualified Data.HashMap.Strict as M
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import Control.Concurrent (forkIO, newEmptyMVar, putMVar, takeMVar)
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import Control.Concurrent.Chan (newChan, writeChan, getChanContents)
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import Control.Monad (foldM, forM_, forM, (>=>))
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import Control.Monad (foldM)
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import Data.Bits (testBit, (.&.), complement, popCount, bit)
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import Data.Char (digitToInt, intToDigit, isDigit)
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import Data.List (foldl', intersperse, intercalate, find, sortBy)
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@ -39,8 +15,6 @@ import Data.List.Split (chunksOf)
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import Data.Maybe (fromJust)
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import Data.Ord (comparing)
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import Data.Word (Word16)
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import System.CPUTime (getCPUTime)
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import Text.Printf (printf)
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-- A cell in the Sudoku. The fields are cell index, possible cell values as
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-- a bitset and number of possible cell values.
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@ -181,77 +155,3 @@ prettyShowBoard board =
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. chunksOf 9
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. showBoard $ board
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where line = "+-------+-------+-------+"
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-- Solves a Sudoku board using recursive backtracking DFS.
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solveSudoku :: Board -> Maybe Board
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solveSudoku board
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-- if solved, return the board
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| isBoardSolved board = Just board
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-- if no more unsolved cells left then return Nothing
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| S.null (ambCells board) = Nothing
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-- if the current cell has no possible values, solve with rest cells
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| val == 0 = solveSudoku $ board { ambCells = cs }
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| otherwise = let
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-- create two cells from current cell, one with only the smallest possible
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-- value and second with the rest
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fs = bit . firstSol $ val
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nextPos = Cell ix fs 1
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restPos = Cell ix (val .&. complement fs) (vl - 1)
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boardR = updateBoard board restPos
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-- try to constrain with the current cell with only one value
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in case constrainBoard board nextPos of
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-- if failed, continue with the current cell with the rest values
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Nothing -> solveSudoku boardR
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-- if solved, return the board
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Just board' | isBoardSolved board' -> Just board'
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-- else try to recursively solve the board further
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| otherwise -> case solveSudoku board' of
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-- if solved, return the board
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Just board'' -> Just board''
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-- else try to solve the board with the current cell
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-- with the rest values
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Nothing -> solveSudoku boardR
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where
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-- Finds the cell which has fewest possible values.
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(Cell ix val vl, cs) = S.deleteFindMin (ambCells board)
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-- Reads the puzzles from stdin and solves them
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main :: IO ()
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main = do
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-- read the puzzles in chunks of 100
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chunks <- fmap (chunksOf 100 . lines) getContents
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solChan <- newChan
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done <- newEmptyMVar
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-- print the solutions (or errors) and wait for all thread to finish
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forkIO $ do
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solutions <- getChanContents solChan
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printSolutions solutions (length chunks)
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putMVar done ()
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-- spawn a thread for each chunk
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forM_ chunks $ \chunk -> forkIO $ do
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-- for each line in the chunk, read it as a Sudoku board and solve it
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-- return solution as a string represented by showBoard if solvable else "Unsolvable"
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-- return an error if invalid board
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forM_ chunk $ \line -> do
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start <- getCPUTime
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let sudoku = readBoard line
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case sudoku of
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Nothing -> writeChan solChan $ "Invalid input sudoku: " ++ line
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Just board -> do
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let !res = solveSudoku board
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end <- getCPUTime
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let diff = fromIntegral (end - start) / (10 ^ 9) :: Double
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let !sol = printf "%s -> %s [%0.3f ms]" line
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(maybe "Unsolvable" showBoard res) diff
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writeChan solChan sol
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writeChan solChan "DONE"
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takeMVar done
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where
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printSolutions _ 0 = return ()
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printSolutions ("DONE":xs) l = printSolutions xs (l - 1)
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printSolutions (x:xs) l = putStrLn x >> printSolutions xs l
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@ -0,0 +1,110 @@
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{-
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A solution to rubyquiz 43 (http://rubyquiz.com/quiz43.html).
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A fast multi-threaded Sudoku solver using recursive depth-first backtracking
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for searching and constraint propagation for solving.
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Solves the 49191 puzzles at http://school.maths.uwa.edu.au/~gordon/sudoku17
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in 32 seconds on a quad core machine with output switched off.
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Each puzzle should be formatted as a single line of 81 character, top to bottom,
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left to right, with digits 1 to 9 if the cell has a value else a dot (.).
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Example:
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4.....8.5.3..........7......2.....6.....8.4......1.......6.3.7.5..2.....1.4......
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Usage:
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cat sudoku17 | bin/SudokuSolver +RTS -N4 -H800m -K50m
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echo "4.....8.5.3..........7......2.....6.....8.4......1.......6.3.7.5..2.....1.4......" | bin/SudokuSolver
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Copyright 2012 Abhinav Sarkar <abhinav@abhinavsarkar.net>
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-}
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{-# LANGUAGE BangPatterns, RecordWildCards #-}
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module Sudoku.Solver (solveSudoku, main) where
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import qualified Data.Set as S
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import Control.Concurrent (forkIO, newEmptyMVar, putMVar, takeMVar)
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import Control.Concurrent.Chan (newChan, writeChan, getChanContents)
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import Control.Monad (forM_, forM)
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import Data.Bits ((.&.), complement, bit)
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import Data.List.Split (chunksOf)
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import System.CPUTime (getCPUTime)
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import Text.Printf (printf)
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import Sudoku.Board
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-- Solves a Sudoku board using recursive backtracking DFS.
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solveSudoku :: Board -> Maybe Board
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solveSudoku board
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-- if solved, return the board
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| isBoardSolved board = Just board
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-- if no more unsolved cells left then return Nothing
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| S.null (ambCells board) = Nothing
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-- if the current cell has no possible values, solve with rest cells
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| val == 0 = solveSudoku $ board { ambCells = cs }
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| otherwise = let
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-- create two cells from current cell, one with only the smallest possible
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-- value and second with the rest
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fs = bit . firstSol $ val
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nextPos = Cell ix fs 1
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restPos = Cell ix (val .&. complement fs) (vl - 1)
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boardR = updateBoard board restPos
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-- try to constrain with the current cell with only one value
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in case constrainBoard board nextPos of
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-- if failed, continue with the current cell with the rest values
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Nothing -> solveSudoku boardR
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-- if solved, return the board
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Just board' | isBoardSolved board' -> Just board'
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-- else try to recursively solve the board further
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| otherwise -> case solveSudoku board' of
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-- if solved, return the board
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Just board'' -> Just board''
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-- else try to solve the board with the current cell
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-- with the rest values
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Nothing -> solveSudoku boardR
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where
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-- Finds the cell which has fewest possible values.
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(Cell ix val vl, cs) = S.deleteFindMin (ambCells board)
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-- Reads the puzzles from stdin and solves them
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main :: IO ()
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main = do
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-- read the puzzles in chunks of 100
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chunks <- fmap (chunksOf 100 . lines) getContents
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solChan <- newChan
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done <- newEmptyMVar
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-- print the solutions (or errors) and wait for all thread to finish
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forkIO $ do
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solutions <- getChanContents solChan
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printSolutions solutions (length chunks)
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putMVar done ()
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-- spawn a thread for each chunk
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forM_ chunks $ \chunk -> forkIO $ do
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-- for each line in the chunk, read it as a Sudoku board and solve it
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-- return solution as a string represented by showBoard if solvable else "Unsolvable"
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-- return an error if invalid board
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forM_ chunk $ \line -> do
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start <- getCPUTime
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let sudoku = readBoard line
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case sudoku of
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Nothing -> writeChan solChan $ "Invalid input sudoku: " ++ line
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Just board -> do
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let !res = solveSudoku board
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end <- getCPUTime
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let diff = fromIntegral (end - start) / (10 ^ 9) :: Double
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let !sol = printf "%s -> %s [%0.3f ms]" line
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(maybe "Unsolvable" showBoard res) diff
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writeChan solChan sol
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writeChan solChan "DONE"
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takeMVar done
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where
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printSolutions _ 0 = return ()
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printSolutions ("DONE":xs) l = printSolutions xs (l - 1)
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printSolutions (x:xs) l = putStrLn x >> printSolutions xs l
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@ -16,8 +16,8 @@ source-repository head
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library
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exposed-modules : AStar, TicTacToe, KnightsTravails, Cryptograms, EnglishNumerals,
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GedcomParser, PhoneNumberWords, SolataireCipher,
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BarrelOfMonkeys, AmazingMazes, SudokuSolver, NumericMaze,
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DiceRoller
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BarrelOfMonkeys, AmazingMazes, Sudoku.Board, Sudoku.Solver,
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NumericMaze, DiceRoller
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build-depends : base == 4.*,
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containers == 0.4.*,
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mtl == 2.1.*,
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@ -114,8 +114,8 @@ executable SudokuSolver
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mtl == 2.1.*,
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split == 0.2.1.*,
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unordered-containers == 0.2.1.*
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main-is : SudokuSolver.hs
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ghc-options : -threaded -rtsopts -fllvm -main-is SudokuSolver
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main-is : Sudoku/Solver.hs
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ghc-options : -threaded -rtsopts -fllvm -main-is Sudoku.Solver
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default-language : Haskell2010
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executable NumericMaze
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