In this recipe, we will conduct two time-consuming tasks in parallel. We will use the rpar function and the rseq function provided by the parallel package from hackage. The rpar function annotates its argument to be evaluated in parallel. The other function, rseq, forces sequential evaluations in what is called the
weak head normal form.
Import the parallel package as follows:
import Control.Parallel import Control.Parallel.Strategies Evaluate two tasks in parallel, and wait for both tasks to finish before returning. main = do print $ runEval $ do a <- rpar task1 b <- rpar task2 rseq a rseq b return (a, b)Perform a time-consuming task as follows:
task1 = 8^8^9 :: Integer
Perform another time-consuming task as follows:
task2 = 8^8^8 :: Integer
Compile the code with the
threadedandrtsoptsflags enabled as follows:$ ghc...