Hello all I am trying to learn parallel Haskell and I have gone through couple of resources ( Real world Haskell and http://research.microsoft.com/en-us/um/people/simonpj/papers/parallel/AFP08-... ). I understood par and pseq and I wrote matrix multiplication using these two function but it does not look. Although I did not get all these details from ( ./Matpar +RTS -N2 -s ) but none of the sparks converted which is really important for parallel programming. Could some one please tell me how to improve this. Also kindly recommend me some literature for parallel programming in Haskell. Regards Mukesh Tiwari import Data.List import Control.Parallel parHelp :: ( Num a ) => [ a ] -> [ a ] -> a parHelp [] [] = 0 parHelp ( x : xs ) ( y : ys ) = ret where ret = par a ( pseq a ( a + parHelp xs ys ) ) where a = x * y helpMult :: ( Num a ) => [ a ] -> [ [ a ] ] -> [ a ] helpMult _ [] = [] helpMult x ( y : ys ) = ret where ret = par a ( pseq a ( a : helpMult x ys ) ) where a = parHelp x y mult :: ( Num a ) => [ [ a ] ] -> [ [ a ] ] -> [ [ a ] ] mult [] _ = [] mult ( x : xs ) ys = ret where ret = par a ( pseq a ( a : mult xs ys ) ) where a = helpMult x ys main = print $ mult [[1 .. 4 ] , [ 1 .. 4 ] , [ 1 .. 4 ] , [ 1 .. 4] ] ( transpose [[1 .. 4 ] , [ 1 .. 4 ] , [ 1 .. 4 ] , [ 1 .. 4] ]) [user@haskell Programming]$ ghc -O2 -threaded -rtsopts Matpar.hs [1 of 1] Compiling Main ( Matpar.hs, Matpar.o ) Linking Matpar ... [user@haskell Programming]$ ./Matpar +RTS -N2 -s ./Matpar +RTS -N2 -s [[10,20,30,40],[10,20,30,40],[10,20,30,40],[10,20,30,40]] 85,480 bytes allocated in the heap 5,216 bytes copied during GC 47,328 bytes maximum residency (1 sample(s)) 22,304 bytes maximum slop 2 MB total memory in use (0 MB lost due to fragmentation) Generation 0: 0 collections, 0 parallel, 0.00s, 0.00s elapsed Generation 1: 1 collections, 0 parallel, 0.00s, 0.00s elapsed Parallel GC work balance: -nan (0 / 0, ideal 2) MUT time (elapsed) GC time (elapsed) Task 0 (worker) : 0.00s ( 0.00s) 0.00s ( 0.00s) Task 1 (worker) : 0.00s ( 0.00s) 0.00s ( 0.00s) Task 2 (bound) : 0.00s ( 0.00s) 0.00s ( 0.00s) Task 3 (worker) : 0.00s ( 0.00s) 0.00s ( 0.00s) * SPARKS: 84 (0 converted, 0 pruned)* INIT time 0.00s ( 0.00s elapsed) MUT time 0.00s ( 0.00s elapsed) GC time 0.00s ( 0.00s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 0.00s ( 0.00s elapsed) %GC time 33.3% (13.5% elapsed) Alloc rate 42,761,380 bytes per MUT second Productivity 33.3% of total user, 45.0% of total elapsed gc_alloc_block_sync: 0 whitehole_spin: 0 gen[0].sync_large_objects: 0 gen[1].sync_large_objects: 0 [user@haskell Programming]$