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| import Control.Parallel -- 'par', 'seq'
import Control.Parallel.Strategies -- parMap
import Data.Array
import Data.Char
import Data.IntSet
import System.IO
import System.Random
boost :: Int
boost = 5
numCities :: Int
numCities = 100
iter :: Int
iter = 4000
input :: String
input = "luxembourg_problem.dat"
output :: String
output = "luxembourg_solution.dat"
-- Матрица является прямоугольным двумерным массивом.
matrix :: Int -> Array (Int,Int) Double
matrix n = array ((0,0),(n-1,n-1)) [((i,j),0.0) | i<-[0..n-1], j<-[0..n-1]]
-- Путь от последнего города к первому.
wrappedPath :: [Int] -> [Int]
wrappedPath path = ((tail path) ++ [(head path)])
pathLength :: Array (Int,Int) Double -> [Int] -> Double
pathLength cities path =
let
f x = cities ! x
pairs = zip path (wrappedPath path)
in
sum (Prelude.map f pairs)
-- Усиление феромонов для городов на путях.
updatePher :: Array (Int,Int) Double -> [Int] -> Array (Int,Int) Double
updatePher pher path =
let
wPath = wrappedPath path
pairs = zip path wPath
incrs = [ (fromIntegral boost) | n <- wPath ]
pairsWithInc = zip pairs incrs
in
accum (+) pher pairsWithInc
-- Испарение феромона.
evaporatePher :: Array (Int,Int) Double -> Int -> Array (Int,Int) Double
evaporatePher pher maxIter =
let
inds = indices pher
decrs = [ ((fromIntegral boost)/(fromIntegral maxIter)) | n <- inds ]
indsWithDecr = zip inds decrs
f x y = if x > y then (x - y) else 0.0
in
accum f pher indsWithDecr
-- Сумма весов для всех путей к городам, примыкающих к данному.
doSumWeight :: Int -> Array (Int,Int) Double -> Array (Int,Int) Double ->
IntSet -> Int -> Double -> Double
doSumWeight city cities pher used current runningTotal =
if city >= numCities then
runningTotal
else
let
incr =
if (member city used) then
0.0
else
(cities!(current, city)) * (1.0 + (pher!(current, city)))
in
doSumWeight (city+1) cities pher used current (runningTotal+incr)
-- Возвращает city в soughtTotal.
findSumWeight :: Int -> Int -> Array (Int,Int) Double ->
Array (Int,Int) Double -> IntSet -> Int -> Double ->
Double -> Int
findSumWeight city nextCity cities pher used current soughtTotal runningTotal =
if (city >= numCities) ||
((not (member city used)) && (runningTotal >= soughtTotal))
then
nextCity
else
let
(incr, nextNextCity) =
if (member city used) then
(0.0, nextCity)
else
((cities!(current,city))*(1.0+(pher!(current, city))),
city)
in
findSumWeight (city+1) nextNextCity cities pher used current
soughtTotal (runningTotal+incr)
-- Возвращает (path, newrGen)
genPathRecurse :: Array (Int,Int) Double -> Array (Int, Int) Double ->
IntSet -> [Int] -> Int -> StdGen -> ([Int],StdGen)
genPathRecurse cities pher used path current rGen =
if (size used) >= numCities then
(path, rGen)
else
let
sumWeight = doSumWeight 0 cities pher used current 0.0
(rndValue, newrGen) = randomR (0.0, sumWeight) rGen
nextCity = findSumWeight 0 0 cities pher used current rndValue 0.0
nextPath = path ++ [nextCity]
nextUsed = insert nextCity used
in
genPathRecurse cities pher nextUsed nextPath nextCity newrGen
-- Возвращает (path, newrGen)
genPath :: Array (Int,Int) Double -> Array (Int, Int) Double -> StdGen ->
([Int], StdGen)
genPath cities pher rGen =
let
(current, newrGen) = randomR (0, numCities-1) rGen
used = insert current empty
path = [current]
in
genPathRecurse cities pher used path current newrGen
-- Возвращает путь
bestPathRecurse :: Array (Int,Int) Double -> Array (Int,Int) Double ->
StdGen -> Int -> Int -> [Int] -> Double -> [Int]
bestPathRecurse cities pher rGen maxIter remainingIter bestPathSoFar
bestLength =
if remainingIter <= 0 then
bestPathSoFar
else
let
(path, newrGen) = genPath cities pher rGen
pathLen = pathLength cities path
(newBestPath,newBestLength,newPher) =
-- Remember we are trying to maximize score.
if pathLen > bestLength then
(path, pathLen, (updatePher pher path))
else
(bestPathSoFar, bestLength, pher)
evaporatedPher = evaporatePher newPher maxIter
in
bestPathRecurse cities evaporatedPher newrGen maxIter
(remainingIter-1) newBestPath newBestLength
-- Возвращает путь
bestPath :: Array (Int,Int) Double -> Int -> Int -> [Int]
bestPath cities rSeed numIter =
let
rGen = mkStdGen rSeed
pher = matrix numCities
in
bestPathRecurse cities pher rGen numIter numIter [] 0.0
-- Возвращает путь
wrapBestPath :: Array (Int,Int) Double -> Int -> Int -> [Int]
wrapBestPath cities rSeed numIter = bestPath cities rSeed numIter
----------------------------------------------------------------------------------
-- Возвращает (path, length)
parallelBestPath :: Array (Int,Int) Double -> Int -> ([Int], Double)
parallelBestPath cities iter =
let
-- 'par' says spark new thread for p1
-- 'seq' says start p2 now also
(path1, path2) = par p1 (seq p2 (p1, p2))
where p1 = wrapBestPath cities 1 iter
p2 = wrapBestPath cities 2 iter
len1 = pathLength cities path1
len2 = pathLength cities path2
(bestPath, bestLen) =
if
len1 > len2
then
(path1,len1)
else
(path2,len2)
in
(bestPath, bestLen)
-- Возвращает (path, length)
parallelBestPathStrategy :: Array (Int,Int) Double -> Int -> ([Int], Double)
parallelBestPathStrategy cities iter =
let
f rSeed = wrapBestPath cities rSeed iter
-- parMap применяет f к каждому элементу списка параллельно
paths = parMap rseq f [1,2]
(path1, path2) = (paths !! 0, paths !! 1)
len1 = pathLength cities path1
len2 = pathLength cities path2
(bestPath, bestLen) =
if
len1 > len2
then
(path1,len1)
else
(path2,len2)
in
(bestPath, bestLen)
----------------------------------------------------------------------------------
-- Преобразование строки GPS-координат к виду (x, y)
readDoubles :: String -> (Double, Double)
readDoubles x = (read y :: Double, read z :: Double)
where y:z:_ = words x
-- Возвращает дистанцию между городами
dist :: (Double, Double) -> (Double, Double) -> Double
dist (x0, y0) (x1, y1) = sqrt $ (x0 - x1) ** 2 + (y0 - y1) ** 2
-- Считывание файла с GPS-координатами
getCoordinats :: String -> IO [(Double, Double)]
getCoordinats file = fmap (Prelude.map readDoubles . Prelude.filter notEmpty . lines) (readFile file)
where notEmpty = not . all isSpace
-- Создание списка из номеров городов и расстояний между ними
distances :: [(Double, Double)] -> [((Int, Int), Double)]
distances coords = let cs = zip [0..] coords in
[ ((i,j), dist x y) | (i,x) <- cs, (j,y) <- cs ]
-- Запуск алгоритма
main :: IO ()
main = do
coordinatsList <- getCoordinats input
handleIn <- openFile input ReadMode
fileContent <- hGetContents handleIn
handleOut <- openFile output WriteMode
let distancesList = distances coordinatsList
cities = array ((0,0), fst $ last distancesList) distancesList
(path, len) = parallelBestPathStrategy cities iter
--(path, len) = parallelBestPath cities iter
mapM (hPutStrLn handleOut) $ Prelude.map (\ x -> (lines fileContent) !! (x-1)) (Prelude.map (+1) path)
hClose handleIn
hClose handleOut
putStrLn $ "Total length : " ++ (show len) |
(
