Thanks for help. I did some tests with UArray and it does the trick. The problem remaining is, how to implement UArray Int (Double, Double, Double)? UArray source code is far too cryptic for me. Regards, Lauri On Fri, May 16, 2008 at 11:37 AM, Bulat Ziganshin wrote:

Hello Lauri,

Friday, May 16, 2008, 12:19:29 PM, you wrote:

...

pixelArray :: Array Int Color

it's boxed array which means that its elements are stored as thunks computed only when you actually use them. try UArray instead:

http://haskell.org/haskellwiki/Modern_array_libraries

-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

Thanks again. Here is my solution in case that somebody else runs into similar problem. This isn't very elegant and I would be interested to know if somebody has a better solution. Surely many people have encountered this kind of problem where you want to force evaluation of some expression at given point of program flow. Here evaluation of sum must be forced for every update of array element or otherwise memory consumption is proportional to the number of samples (100 000) instead of being proportional to the size of the array (10). --- import Data.Array.IO import Test.QuickCheck import System.Random uniformSampler :: Gen Double uniformSampler = choose (0,1) withSeed sampler seed = generate 1 (mkStdGen seed) sampler ac = 10 sc = 100000 triplet = do i <- uniformSampler s <- uniformSampler t <- uniformSampler return (round $ i * fromIntegral ac, (s,t)) sampling = sequence $ repeat triplet samples = take sc $ withSeed sampling 1 showElems xs = foldr1 (++) [show x ++ "\n" | x <- xs] main = do a1 <- newArray (0,ac) 0 :: IO (IOUArray Int Double) a2 <- newArray (0,ac) 0 :: IO (IOUArray Int Double) let addtoElem i s t = do s' <- readArray a1 i writeArray a1 i (s'+s) t' <- readArray a2 i writeArray a2 i (t'+t) writes = [addtoElem i s t | (i,(s,t)) <- samples] sequence writes ss <- getElems a1 ts <- getElems a2 putStrLn $ showElems (zip ss ts) --- Regards, Lauri On Fri, May 16, 2008 at 2:52 PM, Abhay Parvate wrote:

As far as I know, you can't. It needs machine representable types, such as Int, Double, Char, etc. But making a tuple of three UArray Int Double may help.

2008/5/16 Lauri Oksanen :

...

Thanks for help. I did some tests with UArray and it does the trick. The problem remaining is, how to implement UArray Int (Double, Double, Double)? UArray source code is far too cryptic for me.

Regards, Lauri

On Fri, May 16, 2008 at 11:37 AM, Bulat Ziganshin < bulat.ziganshin@gmail.com> wrote:

...

Hello Lauri,

Friday, May 16, 2008, 12:19:29 PM, you wrote:

...

pixelArray :: Array Int Color

it's boxed array which means that its elements are stored as thunks computed only when you actually use them. try UArray instead:

http://haskell.org/haskellwiki/Modern_array_libraries

-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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Hello Lauri, Friday, May 16, 2008, 3:44:19 PM, you wrote: impossible. you can try parallel arrays

Thanks for help. I did some tests with UArray and it does the trick. The problem remaining is, how to implement UArray Int (Double, Double, Double)? UArray source code is far too cryptic for me.

Regards, Lauri

On Fri, May 16, 2008 at 11:37 AM, Bulat Ziganshin wrote: Hello Lauri,

Friday, May 16, 2008, 12:19:29 PM, you wrote:

...

     pixelArray :: Array Int Color

it's boxed array which means that its elements are stored as thunks computed only when you actually use them. try UArray instead:

http://haskell.org/haskellwiki/Modern_array_libraries

-- Best regards,  Bulat                            mailto:Bulat.Ziganshin@gmail.com

-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

Yes, of course. How blind of me. Here is one more question. If you change IOUArray to IOArray and add $! in front of the two summations in the previous code, it still works correctly. But can you do similar trick with Array and accumArray? I have tried to put $! in different places in the first code that I posted but nothing seems to work. On Fri, May 16, 2008 at 4:26 PM, Henning Thielemann < lemming@henning-thielemann.de> wrote:

On Fri, 16 May 2008, Lauri Oksanen wrote:

Thanks for help. I did some tests with UArray and it does the trick.

...

The problem remaining is, how to implement UArray Int (Double, Double, Double)?

Maybe an (UArray (Int,Int) Double) could help, where the second index range is fixed to (0,2).

"Lauri Oksanen" writes:

Thanks for help. I did some tests with UArray and it does the trick. The problem remaining is, how to implement UArray Int (Double, Double, Double)?

As (UArray Int Double, UArray Int Double, UArray Int Double). Or as UArray Int Double, but with a specialized lookup function: mylookup array index = (array!3*index, array!3*index+1, array!3*index+2) I guess it would be possible to have UArray Int (# Double, Double, Double #) - packing all three Doubles unboxed into the array, but I've no clue how to go about automating that. -k -- If I haven't seen further, it is by standing in the footprints of giants