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Today's Topics:
1. Re: parMap on multicore computers (Thomas Friedrich)
2. Re: parMap on multicore computers (Miguel Pignatelli)
3. Re: Catching Network Connection Error (Brent Yorgey)
4. QuickCheck (Thomas Friedrich)
5. Re: QuickCheck (Lee Duhem)
6. Re: QuickCheck (Thomas Friedrich)
7. Re: QuickCheck (Thomas Friedrich)
8. Re: QuickCheck (Lee Duhem)
----------------------------------------------------------------------
Message: 1
Date: Fri, 22 May 2009 18:02:14 -0400
From: Thomas Friedrich <[email protected]>
Subject: Re: [Haskell-beginners] parMap on multicore computers
To: Miguel Pignatelli <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi Miguel,
I don't think that you can expect a program to process each line of a
text file in parallel to very efficient. Opening a new thread is
usually fairly cheap, however, there is some bookkeeping involved that
shouldn't be underestimated. You only have 2 or 4 cores, so opening 100
threads or more, depending on the size of your file, will do you no
good. You should rather split up your file in 4 chunks and and then
process these *4* threads in parallel.
That should make it more efficient! Parallel /= faster. At least not
automatically.
Happy Hacking,
Thomas
Miguel Pignatelli wrote:
> Hi all,
>
> I'm experimenting a bit with the parallelization capabilities of Haskell.
> What I am trying to do is to process in parallel all the lines of a
> text file, calculating the edit distance of each of these lines with a
> given string.
> This is my testing code:
>
>
> import System.IO
> import Control.Monad
> import Control.Parallel
> import Control.Parallel.Strategies
>
> edist :: String -> String -> Int
> -- edist calculates the edit distance of 2 strings
> -- see for
> example http://www.csse.monash.edu.au/~lloyd/tildeFP/Haskell/1998/Edit01/
> <http://www.csse.monash.edu.au/%7Elloyd/tildeFP/Haskell/1998/Edit01/>
>
> getLines :: FilePath -> IO [Int]
> getLines = liftM ((parMap rnf (edist longString)) . lines) . readFile
>
> main :: IO ()
> main = do
> list <- getLines "input.txt"
> mapM_ ( putStrLn . show ) list
>
> I am testing this code in a 2xQuadCore linux (Ubuntu 8.10) machine (8
> cores in total).
> The code has been compiled with
>
> ghc --make -threaded mytest.hs
>
> I've been trying input files of different lengths, but the more cores
> I try to use, the worst performance I am getting.
> Here are some examples:
>
> # input.txt -> 10 lines (strings) of ~1200 letters each
> $ time ./mytest +RTS -N1 > /dev/null
>
> real 0m4.775s
> user 0m4.700s
> sys 0m0.080s
>
> $ time ./mytest +RTS -N4 > /dev/null
>
> real 0m6.272s
> user 0m8.220s
> sys 0m0.290s
>
> $ time ./mytest +RTS -N8 > /dev/null
>
> real 0m7.090s
> user 0m10.960s
> sys 0m0.400s
>
> # input.txt -> 100 lines (strings) of ~1200 letters each
> $ time ./mytest +RTS -N1 > /dev/null
>
> real 0m49.854s
> user 0m49.730s
> sys 0m0.120s
>
> $ time ./mytest +RTS -N4 > /dev/null
>
> real 1m11.303s
> user 1m36.210s
> sys 0m1.070s
>
> $ time ./mytest +RTS -N8 > /dev/null
>
> real 1m19.488s
> user 2m6.250s
> sys 0m1.270s
>
>
> What is going wrong in this code? Is this a problem of the "grain
> size" of the parallelization?
> Any help / advice would be very welcome,
>
> M;
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
------------------------------
Message: 2
Date: Sat, 23 May 2009 12:33:42 +0200
From: Miguel Pignatelli <[email protected]>
Subject: Re: [Haskell-beginners] parMap on multicore computers
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed; delsp=yes
Hi Thomas,
Thanks for your answer.
I know that there is needed some tweak in the process of
parallelization to get a performance gain. I agree with your reasoning
regarding the 100 string input, but in the other example I gave, I use
the 8-core machine to process a 10 strings (and each one takes half a
second to be processed) why is this case failing too?
M;
El 23/05/2009, a las 0:02, Thomas Friedrich escribió:
> Hi Miguel,
>
> I don't think that you can expect a program to process each line of
> a text file in parallel to very efficient. Opening a new thread is
> usually fairly cheap, however, there is some bookkeeping involved
> that shouldn't be underestimated. You only have 2 or 4 cores, so
> opening 100 threads or more, depending on the size of your file,
> will do you no good. You should rather split up your file in 4
> chunks and and then process these *4* threads in parallel.
>
> That should make it more efficient! Parallel /= faster. At least
> not automatically.
>
> Happy Hacking,
> Thomas
>
>
>
> Miguel Pignatelli wrote:
>> Hi all,
>>
>> I'm experimenting a bit with the parallelization capabilities of
>> Haskell.
>> What I am trying to do is to process in parallel all the lines of a
>> text file, calculating the edit distance of each of these lines
>> with a given string.
>> This is my testing code:
>>
>>
>> import System.IO
>> import Control.Monad
>> import Control.Parallel
>> import Control.Parallel.Strategies
>>
>> edist :: String -> String -> Int
>> -- edist calculates the edit distance of 2 strings
>> -- see for example
>> http://www.csse.monash.edu.au/~lloyd/tildeFP/Haskell/1998/Edit01/
>> <http://www.csse.monash.edu.au/%7Elloyd/tildeFP/Haskell/1998/
>> Edit01/>
>>
>> getLines :: FilePath -> IO [Int]
>> getLines = liftM ((parMap rnf (edist longString)) . lines) . readFile
>>
>> main :: IO ()
>> main = do
>> list <- getLines "input.txt"
>> mapM_ ( putStrLn . show ) list
>>
>> I am testing this code in a 2xQuadCore linux (Ubuntu 8.10) machine
>> (8 cores in total).
>> The code has been compiled with
>>
>> ghc --make -threaded mytest.hs
>>
>> I've been trying input files of different lengths, but the more
>> cores I try to use, the worst performance I am getting.
>> Here are some examples:
>>
>> # input.txt -> 10 lines (strings) of ~1200 letters each
>> $ time ./mytest +RTS -N1 > /dev/null
>> real 0m4.775s
>> user 0m4.700s
>> sys 0m0.080s
>>
>> $ time ./mytest +RTS -N4 > /dev/null
>>
>> real 0m6.272s
>> user 0m8.220s
>> sys 0m0.290s
>>
>> $ time ./mytest +RTS -N8 > /dev/null
>>
>> real 0m7.090s
>> user 0m10.960s
>> sys 0m0.400s
>>
>> # input.txt -> 100 lines (strings) of ~1200 letters each
>> $ time ./mytest +RTS -N1 > /dev/null
>>
>> real 0m49.854s
>> user 0m49.730s
>> sys 0m0.120s
>>
>> $ time ./mytest +RTS -N4 > /dev/null
>>
>> real 1m11.303s
>> user 1m36.210s
>> sys 0m1.070s
>>
>> $ time ./mytest +RTS -N8 > /dev/null
>>
>> real 1m19.488s
>> user 2m6.250s
>> sys 0m1.270s
>>
>>
>> What is going wrong in this code? Is this a problem of the "grain
>> size" of the parallelization?
>> Any help / advice would be very welcome,
>>
>> M;
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Beginners mailing list
>> [email protected]
>> http://www.haskell.org/mailman/listinfo/beginners
>>
>
>
------------------------------
Message: 3
Date: Sat, 23 May 2009 09:56:32 -0400
From: Brent Yorgey <[email protected]>
Subject: Re: [Haskell-beginners] Catching Network Connection Error
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
On Fri, May 22, 2009 at 01:20:39AM -0500, aditya siram wrote:
> Hi all,
> I am trying to Network.HTTP to connect to a website and catch the error if
> the network is down. Here's what I have so far:
>
> data Errors = DocumentParseError
> | WebsiteUnreachableError
> | ISBNNotFoundError
>
> respHTML' :: ISBN -> IO (Either Errors (IO String))
> respHTML' isbn =
> do
> rsp <- simpleHTTP (getRequest $ "
> http://isbndb.com/api/books.xml?results=details&access_key=";
> ++ key
> ++ "&index1=isbn&value1="
> ++ isbn :: Request_String)
> return $ Right $ getResponseBody rsp
> `E.catch` (\(e :: E.SomeException ) ->
> return $ Left $ WebsiteUnreachableError)
>
> I get the following error when I load it into GHCI:
> Couldn't match expected type `[Char]'
> against inferred type `Either Errors b'
> Expected type: IO String
> Inferred type: IO (Either Errors b)
> In the expression: return $ Left $ WebsiteUnreachableError
> In the second argument of `E.catch', namely
> `(\ (e :: E.SomeException)
> -> return $ Left $ WebsiteUnreachableError)'
> Failed, modules loaded: none.
>
> Control.Exception.catch has the following signature :
> catch :: forall a. IO a -> (IOError -> IO a) -> IO a
>
> I would expect that the handler function needs to return an IO (Either
> Errors (IO String)). Why is it trying to return an IO String?
Because the call to 'catch' only applies to 'getResponseBody rsp',
which is already inside the 'return $ Right $'. Perhaps you want to
put parentheses around (return $ Right $ getResponseBody rsp) ?
-Brent
------------------------------
Message: 4
Date: Sat, 23 May 2009 23:08:47 -0400
From: Thomas Friedrich <[email protected]>
Subject: [Haskell-beginners] QuickCheck
To: beginners <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hallo everyone,
I am currently playing around with the QuickCheck library. I came
across the
Test.QuickCheck.Batch
module a couple of times. I don't seem to have this module installed?
Where can I get it and how do I install it?
I also would like to invoke the following in ghci.
generate 10 (System.Random.mkStdGen 1) arbitrary :: [Int]
However, the function `generate` doesn't get imported when importing
QuickCheck, and I just cannot find out which module this one would be in.
I came to the conclusion that `generate` is just not the best word for a
google search :(
Cheers,
Thomas
------------------------------
Message: 5
Date: Sun, 24 May 2009 11:21:57 +0800
From: Lee Duhem <[email protected]>
Subject: Re: [Haskell-beginners] QuickCheck
To: Thomas Friedrich <[email protected]>
Cc: beginners <[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=UTF-8
On Sun, May 24, 2009 at 11:08 AM, Thomas Friedrich <[email protected]> wrote:
> Hallo everyone,
>
> I am currently playing around with the QuickCheck library. Â I came across
> the
>
> Test.QuickCheck.Batch
>
> module a couple of times. Â I don't seem to have this module installed?
> Â Where can I get it and how do I install it?
If you use GHC, you already have it, try
ghc-pkg list | grep -i quickcheck
>
> I also would like to invoke the following in ghci.
>
> generate 10 (System.Random.mkStdGen 1) arbitrary :: [Int]
>
> However, the function `generate` doesn't get imported when importing
> QuickCheck, and I just cannot find out which module this one would be in.
In GHCi, you need import Test.QuickCheck or Debug.QuickCheck before
you use generate.
>
> I came to the conclusion that `generate` is just not the best word for a
> google search :(
Just check the document of GHC libraries:
http://www.haskell.org/ghc/docs/latest/html/libraries/index.html
http://www.haskell.org/ghc/docs/latest/html/libraries/QuickCheck/Test-QuickCheck.html
lee
------------------------------
Message: 6
Date: Sat, 23 May 2009 23:25:23 -0400
From: Thomas Friedrich <[email protected]>
Subject: Re: [Haskell-beginners] QuickCheck
To: Lee Duhem <[email protected]>, beginners <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi Lee,
I do have GHC and no, I seem to not have it.
$ ghc-pkg list | grep -i quickcheck
Cabal-1.6.0.3, Chart-0.10.3, HUnit-1.2.0.3, QuickCheck-1.2.0.0,
Diff-0.1.2, QuickCheck-2.1.0.1, binary-0.5.0.1,
When I am in ghci, I have the following options:
Prelude> :m +Test.QuickCheck
Test.QuickCheck Test.QuickCheck.Function
Test.QuickCheck.Monadic Test.QuickCheck.Property Test.QuickCheck.Test
Test.QuickCheck.Arbitrary Test.QuickCheck.Gen
Test.QuickCheck.Poly Test.QuickCheck.State Test.QuickCheck.Text
Prelude> :m +Test.QuickCheck
But no Test.QuickCheck.Batch
:(
Cheers,
Thomas
Lee Duhem wrote:
> On Sun, May 24, 2009 at 11:08 AM, Thomas Friedrich <[email protected]> wrote:
>
>> Hallo everyone,
>>
>> I am currently playing around with the QuickCheck library. I came across
>> the
>>
>> Test.QuickCheck.Batch
>>
>> module a couple of times. I don't seem to have this module installed?
>> Where can I get it and how do I install it?
>>
>
> If you use GHC, you already have it, try
> ghc-pkg list | grep -i quickcheck
>
>
>> I also would like to invoke the following in ghci.
>>
>> generate 10 (System.Random.mkStdGen 1) arbitrary :: [Int]
>>
>> However, the function `generate` doesn't get imported when importing
>> QuickCheck, and I just cannot find out which module this one would be in.
>>
>
> In GHCi, you need import Test.QuickCheck or Debug.QuickCheck before
> you use generate.
>
>
>> I came to the conclusion that `generate` is just not the best word for a
>> google search :(
>>
>
> Just check the document of GHC libraries:
> http://www.haskell.org/ghc/docs/latest/html/libraries/index.html
> http://www.haskell.org/ghc/docs/latest/html/libraries/QuickCheck/Test-QuickCheck.html
>
> lee
>
------------------------------
Message: 7
Date: Sat, 23 May 2009 23:47:06 -0400
From: Thomas Friedrich <[email protected]>
Subject: Re: [Haskell-beginners] QuickCheck
To: beginners <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi folks,
I did the following and now it works. I had a closer look at my ghc-pkg
list (thanks for the tip), which looked like the following:
$ ghc-pkg list
/usr/lib/ghc-6.10.3/./package.conf:
Cabal-1.6.0.3, Chart-0.10.3, HUnit-1.2.0.3, QuickCheck-1.2.0.0,
X11-1.4.5, array-0.2.0.0, base-3.0.3.1, base-4.1.0.0,
bytestring-0.9.1.4, cairo-0.10.1, containers-0.2.0.1,
data-accessor-0.2.0.2, data-accessor-template-0.2.1.1,
directory-1.0.0.3, (dph-base-0.3), (dph-par-0.3),
(dph-prim-interface-0.3), (dph-prim-par-0.3), (dph-prim-seq-0.3),
(dph-seq-0.3), extensible-exceptions-0.1.1.0, filepath-1.1.0.2,
gconf-0.10.1, (ghc-6.10.3), ghc-prim-0.1.0.0, glade-0.10.1,
glib-0.10.1, gtk-0.10.1, gtkglext-0.10.1, gtksourceview2-0.10.1,
haddock-2.4.2, haskell-src-1.0.1.3, haskell98-1.0.1.0, hpc-0.5.0.3,
html-1.0.1.2, integer-0.1.0.1, mtl-1.1.0.2, network-2.2.1,
old-locale-1.0.0.1, old-time-1.0.0.2, packedstring-0.1.0.1,
parallel-1.1.0.1, parsec-2.1.0.1, pretty-1.0.1.0, process-1.0.1.1,
random-1.0.0.1, regex-base-0.72.0.2, regex-compat-0.71.0.1,
regex-posix-0.72.0.3, rts-1.0, soegtk-0.10.1, stm-2.1.1.2,
svgcairo-0.10.1, syb-0.1.0.1, template-haskell-2.3.0.1, time-1.1.3,
transformers-0.1.4.0, unix-2.3.2.0, utf8-string-0.3.4,
utility-ht-0.0.5.1, xhtml-3000.2.0.1, xmonad-0.8.1,
xmonad-contrib-0.8.1
/home/thomas/.ghc/i386-linux-6.10.3/package.conf:
Diff-0.1.2, QuickCheck-2.1.0.1, binary-0.5.0.1,
data-accessor-monads-fd-0.2, derive-0.1.4, dotgen-0.2,
fingertree-0.0, ghc-paths-0.1.0.5, haskell-lexer-1.0,
monads-fd-0.0.0.1, pointedlist-0.3.3, pureMD5-0.2.4,
regex-base-0.93.1, regex-tdfa-1.0.0, rosezipper-0.1, split-0.1.1,
terminfo-0.3.0.2, uniplate-1.2.0.3, unix-compat-0.1.2.1,
vty-3.1.8.4, yi-0.6.0
I think because I installed yi, I must have also ended up with the
QuickCheck-2.1.0.1 package. In this package there is NO `generate`, no
`verboseCheck` and other functions available. (Why?? Does anyone
know?) Also there is no QuickCheck.Batch.
Simply hiding the package solved the problem, by
ghc-pkg hide QuickCheck-2.1.0.1
Now, I can also use the Batch module.
Does anyone know why the now version of QuickCheck is not compatible
with the old one?
Best,
Thomas
Thomas Friedrich wrote:
> Hi Lee,
>
> I do have GHC and no, I seem to not have it.
>
> $ ghc-pkg list | grep -i quickcheck
> Cabal-1.6.0.3, Chart-0.10.3, HUnit-1.2.0.3, QuickCheck-1.2.0.0,
> Diff-0.1.2, QuickCheck-2.1.0.1, binary-0.5.0.1,
>
>
> When I am in ghci, I have the following options:
>
> Prelude> :m +Test.QuickCheck
> Test.QuickCheck Test.QuickCheck.Function
> Test.QuickCheck.Monadic Test.QuickCheck.Property
> Test.QuickCheck.Test
> Test.QuickCheck.Arbitrary Test.QuickCheck.Gen
> Test.QuickCheck.Poly Test.QuickCheck.State
> Test.QuickCheck.Text
> Prelude> :m +Test.QuickCheck
>
> But no Test.QuickCheck.Batch
>
> :(
>
> Cheers,
> Thomas
>
>
> Lee Duhem wrote:
>> On Sun, May 24, 2009 at 11:08 AM, Thomas Friedrich <[email protected]> wrote:
>>
>>> Hallo everyone,
>>>
>>> I am currently playing around with the QuickCheck library. I came
>>> across
>>> the
>>>
>>> Test.QuickCheck.Batch
>>>
>>> module a couple of times. I don't seem to have this module installed?
>>> Where can I get it and how do I install it?
>>>
>>
>> If you use GHC, you already have it, try
>> ghc-pkg list | grep -i quickcheck
>>
>>
>>> I also would like to invoke the following in ghci.
>>>
>>> generate 10 (System.Random.mkStdGen 1) arbitrary :: [Int]
>>>
>>> However, the function `generate` doesn't get imported when importing
>>> QuickCheck, and I just cannot find out which module this one would
>>> be in.
>>>
>>
>> In GHCi, you need import Test.QuickCheck or Debug.QuickCheck before
>> you use generate.
>>
>>
>>> I came to the conclusion that `generate` is just not the best word
>>> for a
>>> google search :(
>>>
>>
>> Just check the document of GHC libraries:
>> http://www.haskell.org/ghc/docs/latest/html/libraries/index.html
>> http://www.haskell.org/ghc/docs/latest/html/libraries/QuickCheck/Test-QuickCheck.html
>>
>>
>>
>> lee
>>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
------------------------------
Message: 8
Date: Sun, 24 May 2009 11:49:17 +0800
From: Lee Duhem <[email protected]>
Subject: Re: [Haskell-beginners] QuickCheck
To: Thomas Friedrich <[email protected]>
Cc: beginners <[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=UTF-8
On Sun, May 24, 2009 at 11:25 AM, Thomas Friedrich <[email protected]> wrote:
> Hi Lee,
>
> I do have GHC and no, I seem to not have it.
>
> $ ghc-pkg list | grep -i quickcheck
> Â Cabal-1.6.0.3, Chart-0.10.3, HUnit-1.2.0.3, QuickCheck-1.2.0.0,
> Â Diff-0.1.2, QuickCheck-2.1.0.1, binary-0.5.0.1,
Did you notice that you have two QuickCheck installed?
>
>
> When I am in ghci, I have the following options:
>
> Prelude> :m +Test.QuickCheck
> Test.QuickCheck       Test.QuickCheck.Function
> Test.QuickCheck.Monadic   Test.QuickCheck.Property  Test.QuickCheck.Test
> Test.QuickCheck.Arbitrary  Test.QuickCheck.Gen   Â
> Â Test.QuickCheck.Poly
>   Test.QuickCheck.State    Test.QuickCheck.Text
> Prelude> :m +Test.QuickCheck
>
> But no Test.QuickCheck.Batch
>
I guess you use QuickCheck-2.1 instead of 1.2, and Test.QuickCheck.Batch
in QuickCheck-1.2, not in 2.1
lee
------------------------------
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End of Beginners Digest, Vol 11, Issue 16
*****************************************
