Hi all,
I'm seeing no performance increase with a simple coarse-grained
2-thread code using Control.Concurrent. I compile with:
> hc conc.hs -o conc --make -threaded
and I run with
> time ./conc +RTS -N2
But using either "-N1" or "-N2", the program runs in about 1.8secs.
(I'd prefer a longer
On Fri, Dec 19, 2008 at 2:27 PM, Paul Keir wrote:
> I'm seeing no performance increase with a simple coarse-grained
> 2-thread code using Control.Concurrent. I compile with:
I didn't test your code, but
[...]
> fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
> heavytask m = putMVar m (fibs !! 10
pkeir:
> Hi all,
>
> I'm seeing no performance increase with a simple coarse-grained
> 2-thread code using Control.Concurrent. I compile with:
>
> > hc conc.hs -o conc --make -threaded
Also, if you care about performance in the slightest , please use -O2
Code is typically 10-30x faster with opt
On Fri, Dec 19, 2008 at 9:27 AM, Paul Keir wrote:
> Hi all,
>
> I'm seeing no performance increase with a simple coarse-grained
> 2-thread code using Control.Concurrent. I compile with:
>
> > hc conc.hs -o conc --make -threaded
>
> and I run with
>
> > time ./conc +RTS -N2
>
> But using either
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Paul Keir wrote:
> fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
This is a CAF (Constant Applicative Form). Since it is actually a
constant it is never garbage collected, and is always shared, so each
thread is only calculating it once. You have essenti
On Fri, Dec 19, 2008 at 9:27 AM, Paul Keir wrote:
> module Main where
>
> import Control.Concurrent
>
> fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
>
> heavytask m = putMVar m (fibs !! 10)
Oh, also, heavytask is not very heavy at all. It just writes the thunk
(fibs !! 10) into the MVar
I did indeed intend for the threads to evaluate before writing to the
two variables, thanks.
> heavytask m = putMVar m $! (fibs !! 10)
I now see a time difference, but as you suggested, in the wrong
direction (1.5s for one, and 3.6s for two threads). I was hoping
for each thread to independen
On Fri, Dec 19, 2008 at 3:16 PM, Paul Keir wrote:
> can I not expect each thread to run on a separate core?
Try moving 'fibs' inside 'heavyTask', like
heavytask m = putMVar m $! (let fibs = 0 : 1 : zipWith (+) fibs (tail
fibs) in (fibs !! 10))
Maybe this may trick the compiler into not shar
On Fri, 2008-12-19 at 10:42 -0600, Jake McArthur wrote:
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>
> Paul Keir wrote:
> > fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
>
> This is a CAF (Constant Applicative Form). Since it is actually a
> constant it is never garbage collected, and is alw
> So this benchmark is primarily a stress test of the parallel garbage
> collector since it is GC that is taking 75-80% of the time. Note that
> the mutator elapsed time goes down slightly with 2 cores compared to 1
> however the GC elapsed time goes up slightly.
Thanks Duncan, Jake et al. I'm mor
Thanks Luke, and everyone else. Ok, back to the drawing board.
Paul
From: Luke Palmer [mailto:lrpal...@gmail.com]
Sent: 19 December 2008 16:44
To: Paul Keir
Cc: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] forkIO on multicore[MESSAGE NOT SCANNED]
On Fri, Dec 19, 2008 at 9:27
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Paul Keir wrote:
> Thanks Luke, and everyone else. Ok, back to the drawing board.
You may be interested in this:
http://cgi.cse.unsw.edu.au/~dons/blog/2007/11/29
- - Jake
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Comment: Using
Hi Duncan,
I'm following the story regarding (parallel) GC in this example
with interest, but forgive me if I ask a more minor question
regarding your modification of an extra parameter, "n", to
"heavytask". Does this really help (to ensure that each core
does work independently)? Surely, with fib
On Tue, 2008-12-23 at 18:27 +, Paul Keir wrote:
> Hi Duncan,
>
> I'm following the story regarding (parallel) GC in this example
> with interest, but forgive me if I ask a more minor question
> regarding your modification of an extra parameter, "n", to
> "heavytask". Does this really help (to
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