Resetable CountDownLatch

[Timo Nentwig-5]

Hi!

I'm looking for something like a resetable CountDownLatch. Here's what I want
to do: n thread render an image in parallel (each calling countDown() when
done) and when all threads are finished, some logic (i.e. drawing to screen)
needs to be executed. And then start all over again.

I didn't find anything that fits in j.u.c. :-\

thx
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[David Holmes-6]

Hi,

> I'm looking for something like a resetable CountDownLatch. Here's
> what I want to do: n thread render an image in parallel (each
> calling countDown() when done) and when all threads are finished,
> some logic (i.e. drawing  to screen) needs to be executed. And
> then start all over again.

You could just create a new CountDownLatch on each iteration.

Alternatively if you don't care about blocking the rendering threads across
iterations use a CyclicBarrier - the barrier action then makes it easy to do
the logic on completion.

David Holmes

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[Armin Hopp]

Hi Timo,

you should take a look at the Phaser class.

cheers
Armin

Timo Nentwig schrieb:

> Hi!
>
> I'm looking for something like a resetable CountDownLatch. Here's what I want
> to do: n thread render an image in parallel (each calling countDown() when
> done) and when all threads are finished, some logic (i.e. drawing to screen)
> needs to be executed. And then start all over again.
>
> I didn't find anything that fits in j.u.c. :-\
>
> thx
> _______________________________________________
> Concurrency-interest mailing list
> Concurrency-interest@...
> http://cs.oswego.edu/mailman/listinfo/concurrency-interest
>  

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[David Holmes-6]

Armin Hopp wrote
>
> you should take a look at the Phaser class.

Yes - good point! But as this is a new class for JDK7 it might not be
applicable yet.

David Holmes

> cheers
> Armin
>
> Timo Nentwig schrieb:
> > Hi!
> >
> > I'm looking for something like a resetable CountDownLatch.
> Here's what I want
> > to do: n thread render an image in parallel (each calling
> countDown() when
> > done) and when all threads are finished, some logic (i.e.
> drawing to screen)
> > needs to be executed. And then start all over again.
> >
> > I didn't find anything that fits in j.u.c. :-\
> >
> > thx
> > _______________________________________________
> > Concurrency-interest mailing list
> > Concurrency-interest@...
> > http://cs.oswego.edu/mailman/listinfo/concurrency-interest
> >
>
>

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[martinrb]

On Sat, Oct 10, 2009 at 14:57, David Holmes <davidcholmes@...> wrote:
>
> Armin Hopp wrote
>>
>> you should take a look at the Phaser class.
>
> Yes - good point! But as this is a new class for JDK7 it might not be
> applicable yet.

Our intent is to support the version of Phaser in the jsr166y package
for the forseeable future, to be usable as a third-party add-on to jdk6.

Martin
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[Jed Wesley-Smith]

Forgive me if I am wrong, but might a better way to model this be  
using the forkJoin framework? The basic idea being that you submit a  
render action to a fork join executor that will devolve into the  
recurse actions that render each image part and when they all become  
available, draws the image or makes it available to the draw queue.

cheers,
jed.

On 10/10/2009, at 9:13 PM, Timo Nentwig <concurrency-
interest@...> wrote:

> Hi!
>
> I'm looking for something like a resetable CountDownLatch. Here's  
> what I want
> to do: n thread render an image in parallel (each calling countDown
> () when
> done) and when all threads are finished, some logic (i.e. drawing to  
> screen)
> needs to be executed. And then start all over again.
>
> I didn't find anything that fits in j.u.c. :-\
>
> thx
> _______________________________________________
> Concurrency-interest mailing list
> Concurrency-interest@...
> http://cs.oswego.edu/mailman/listinfo/concurrency-interest

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[Armin Hopp]

Hi Jed, Timo

I agree with you. I implemented a grayscaler using FJ once, though with
something fast like a grayscaler you might not get a speedup with small
to normal sized images. Also you have to work double buffered if you
need surrounding pixel to calculate the new pixel color. On large images
you probably only want to double buffer border pixels which blows up the
straight-forwardness of the implementation. But all in all I would still
try to fit it into an RecursiveAction.
As far as Timos explanations let as understand his problem, I say it
practically begs for a FJ implementation.

cheers
Armin

Jed Wesley-Smith schrieb:

> Forgive me if I am wrong, but might a better way to model this be
> using the forkJoin framework? The basic idea being that you submit a
> render action to a fork join executor that will devolve into the
> recurse actions that render each image part and when they all become
> available, draws the image or makes it available to the draw queue.
>
> cheers,
> jed.
>
> On 10/10/2009, at 9:13 PM, Timo Nentwig
> <concurrency-interest@...> wrote:
>
>> Hi!
>>
>> I'm looking for something like a resetable CountDownLatch. Here's
>> what I want
>> to do: n thread render an image in parallel (each calling countDown()
>> when
>> done) and when all threads are finished, some logic (i.e. drawing to
>> screen)
>> needs to be executed. And then start all over again.
>>
>> I didn't find anything that fits in j.u.c. :-\
>>
>> thx
>> _______________________________________________
>> Concurrency-interest mailing list
>> Concurrency-interest@...
>> http://cs.oswego.edu/mailman/listinfo/concurrency-interest
> _______________________________________________
> Concurrency-interest mailing list
> Concurrency-interest@...
> http://cs.oswego.edu/mailman/listinfo/concurrency-interest

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