Чтение текстового файла

results

$ ls -l test.txt 
-rw-rw-r-- 1 blaze blaze 69979380 Aug 26 12:08 test.txt
$ wc -l test.txt 
8994700 test.txt

Strict Data.Bytestring + decodeUtf8  -- 5 секунд
Strict Data.Text.IO -- 7 секунд
Lazy Data.Bytestring + decodeUtf8  -- 10 секунд
Lazy Data.Text.IO -- 12 секунд

test.hs

{-# LANGUAGE BangPatterns #-}
module Main where

-- Lazy добавлять и удалять по желанию
import qualified Data.Text.Lazy as T
import qualified Data.Text.Lazy.Read as T
import qualified Data.Text.Lazy.IO as T
import qualified Data.Text.Lazy.Encoding as T
import qualified Data.ByteString.Lazy as BS

import qualified Data.Map as M
import Data.List

addval :: M.Map Int [Int] -> T.Text -> M.Map Int [Int]
addval !g t
    | M.member k g = M.adjust (v :) k g
    | otherwise = M.insert k [v] g
    where
    [Right (k, _), Right (v, _)] = map T.decimal $ T.words t

main :: IO ()
main = do
    t <- T.readFile "test.txt"
--    bs <- BS.readFile "test.txt"
--    let t = T.decodeUtf8 bs
    let g = foldl' addval M.empty $ T.lines t
    _ <- g `seq` return g
    --print g
    return ()