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Today's Topics:
1. Concurrent vs GHC (Mauricio Hernandes)
2. Re: Concurrent vs GHC (Felipe Almeida Lessa)
3. Re: Concurrent vs GHC (Mauricio Hernandes)
----------------------------------------------------------------------
Message: 1
Date: Sun, 1 Jul 2012 00:03:34 +0900
From: Mauricio Hernandes <[email protected]>
Subject: [Haskell-beginners] Concurrent vs GHC
To: [email protected]
Message-ID:
<caoons7zurxzpyejxp-wxlutfbx+jdstrhfnvaq2+5w8f9_r...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello, I'm having a problem with GHC.
When I compile the code bellow it does nothing, but If I try to use ghci it
works normally.
it seems a simple problem, but I can't understand.
Thanks for the help
Mauricio
import System.IO
import Control.Concurrent
import Data.List
main = do
input <- newMVar [1..30000]
ia <- newEmptyMVar
ib <- newEmptyMVar
ic <- newEmptyMVar
forkIO $ do x <- readMVar input
putMVar ia x
forkIO $ do a <- readMVar ia
putMVar ib ( sum a )
forkIO $ do a <- readMVar ia
putMVar ic ( reverse a )
forkIO $ do b <- readMVar ib
c <- readMVar ic
print b
print c
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Message: 2
Date: Sat, 30 Jun 2012 12:24:02 -0300
From: Felipe Almeida Lessa <[email protected]>
Subject: Re: [Haskell-beginners] Concurrent vs GHC
To: [email protected]
Cc: [email protected]
Message-ID:
<CANd=ogeerxzpn116cqlpoddvassuebynwrbrg2tp4j3q9ob...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Your application is exiting before your forkIOs get a chance to
execute. Instead of
forkIO $ do
...
forkIO $ do
...
forkIO $ do
...
use something like
finished <- newEmptyMVar
forkIO $ do
...
putMVar finished ()
forkIO $ do
...
putMVar finished ()
forkIO $ do
...
putMVar finished ()
replicateM_ 3 (takeMVar finished)
Doing so will avoid your program to exit until all threads have finished.
Note that the code above is extremely fragile: doesn't handle
exceptions, you have to manually specify the number of threads that
you opened, etc. These are abstracted by some libraries on Hackage
that you may use later for Real World Code (TM).
Cheers, =)
--
Felipe.
------------------------------
Message: 3
Date: Sun, 1 Jul 2012 02:51:27 +0900
From: Mauricio Hernandes <[email protected]>
Subject: Re: [Haskell-beginners] Concurrent vs GHC
To: Felipe Almeida Lessa <[email protected]>
Cc: [email protected]
Message-ID:
<CAOons7a6j9Mws-CTHJvRr5zHFQXmVX7-tpzq=xt0hpnjoej...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Eternal Gratitude for the help, it's working perfectly, I will consider the
exceptions and other stuff now.
the code looks like this now
import System.IO
import Control.Concurrent
import Data.List
import Control.Monad
main = do
finished <- newEmptyMVar
input <- newMVar [1..30000]
ia <- newEmptyMVar
ib <- newEmptyMVar
ic <- newEmptyMVar
forkIO $ do x <- readMVar input
putMVar ia x
putMVar finished ()
forkIO $ do a <- readMVar ia
putMVar ib ( sum a )
putMVar finished ()
forkIO $ do a <- readMVar ia
putMVar ic ( reverse a )
putMVar finished ()
b <- readMVar ib
c <- readMVar ic
writeFile "somaEprod.txt" (show b ++ "\n")
appendFile "somaEprod.txt" (show c)
replicateM_ 3 (takeMVar finished)
Valeu
Mauricio
On Sun, Jul 1, 2012 at 12:24 AM, Felipe Almeida Lessa <
[email protected]> wrote:
> Your application is exiting before your forkIOs get a chance to
> execute. Instead of
>
> forkIO $ do
> ...
> forkIO $ do
> ...
> forkIO $ do
> ...
>
> use something like
>
> finished <- newEmptyMVar
>
> forkIO $ do
> ...
> putMVar finished ()
>
> forkIO $ do
> ...
> putMVar finished ()
>
> forkIO $ do
> ...
> putMVar finished ()
>
> replicateM_ 3 (takeMVar finished)
>
> Doing so will avoid your program to exit until all threads have finished.
>
> Note that the code above is extremely fragile: doesn't handle
> exceptions, you have to manually specify the number of threads that
> you opened, etc. These are abstracted by some libraries on Hackage
> that you may use later for Real World Code (TM).
>
> Cheers, =)
>
> --
> Felipe.
>
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