Hello all I am trying to convert List of Lists ( [[(Int , Double )]] ) into PArray ( PArray ( Int , Double )) but getting run time error. This code works fine and print list of PArray ( Int , Double ) but when i put print $ P.fromList ( map P.fromList c ) then i am getting runtime error. It says "Main: Data/Array/Parallel/PArray/PDataInstances.hs:337:10-30: No instance nor default method for class operation Data.Array.Parallel.PArray.PData.fromListPR". Could some one please tell me how to resolve this issue. Thank you --import ParallelMat import Data.List import System.Environment import Data.Array.Parallel import qualified Data.Array.Parallel.PArray as P processMatrix :: [ [ Double ] ] -> [ [ Double ] ] -> [ ( [ ( Int , Double ) ] , [ ( Int , Double ) ]) ] processMatrix [] [] = [] processMatrix ( x : xs ) ( y : ys ) | ( all ( == 0 ) x ) Prelude.|| ( all ( == 0 ) y ) = processMatrix xs ys | otherwise = ( filter ( \( x , y ) -> y /= 0 ) . zip [ 1..] $ x ,filter ( \( x , y ) -> y /= 0 ) . zip [1..] $ y ) : processMatrix xs ys main = do [ first , second ] <- getArgs a <- readFile first b <- readFile second let a' = transpose . tail . map ( map ( read :: String -> Double ) . words ) . lines $ a b' = tail . map ( map ( read :: String -> Double ) . words ) . lines $ b ( c , d ) = unzip $ processMatrix a' b' print $ ( map P.fromList c ) --print d Macintosh-0026bb610428:Haskell mukesh$ ghc --make -Odph -fdph-par Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Linking Main ... Macintosh-0026bb610428:Haskell mukesh$ ./Main A.in A.in [fromList<PArray> [(1,1.0),(6,1.0)],fromList<PArray> [(4,11.0),(9,11.0)],fromList<PArray> [(1,4.0),(4,2.0),(6,4.0),(9,2.0)]] Putting print $ P.fromList ( map P.fromList c ) Macintosh-0026bb610428:Haskell mukesh$ ghc --make -Odph -fdph-par Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Linking Main ... Macintosh-0026bb610428:Haskell mukesh$ ./Main A.in A.in Main: Data/Array/Parallel/PArray/PDataInstances.hs:337:10-30: No instance nor default method for class operation Data.Array.Parallel.PArray.PData.fromListPR Input file A.in 10 10 1 2 3 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 11 2 0 1 2 0 0 0 0 0 0 0 1 2 3 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 11 2 0 1 2 0 0 0 0 0 0 0