[Haskell-cafe] [reactive] A pong and integrate

[Limestraël]

Eventually, I don't think it is a profiling issue.
Maybe a problem with integral. According to a quite recent post on the
reactive mailing list, the following minimal code produces the same problem
:

> import FRP.Reactive
> import FRP.Reactive.LegacyAdapters

> import Control.Applicative

> type Velocity = Double
> type Position = Double

> data Car = Car { vel :: Velocity, pos :: Position } deriving Show

> velocity :: Behavior Velocity

> velocity = 1

> position :: Behavior Position
> position = integral (atTimes [0, 0.5 ..]) velocity

> car :: Behavior Car
> car = Car <$> velocity <*> position


> main :: IO ()
> main = adaptE $ print <$> car `snapshot_` atTimes [0, 0.5..]

> 1) why is the leak happen?
> 2) how can I fix this problem?

> Some more detailed informations:

> * reactive 0.11.4
> * GHC 6.12.1
> * Gentoo Linux (2.6.32-tuxonice, x86_64) or Ubuntu 9.10 64bits
> * compiled with or without -O2 flag



2010/5/16 David Leimbach <leimy2k at gmail.com>

>
>
> On Sat, May 15, 2010 at 8:42 AM, Limestraël <limestrael at gmail.com> wrote:
>
>> Okay,
>> guess I'll have to bring out the chapter 25 of my Real World Haskell...
>>
>
> I find it's often the most practical chapter that I hit a lot during writes
> and changes to my server process I have in Haskell in our control system
> code :-)
>
> That plus the information that I had missed that Control.Monad.State
> defaulted to the Lazy version (which is consistent, but for some reason it
> got by me) helped me to realize why I was leaking so much space in a garbage
> collected environment.
>
> I wouldn't have gotten very far with Haskell as this piece of our code
> without that chapter.  I'd love to see more writing of that sort around
> Haskell in book form.  One can become fluent in tuning Haskell by trial and
> error, but the sharp corners one must bump into are often sharper than in
> other languages I've found.
>
> Dave
>
>
>>
>>
>> 2010/5/15 Bulat Ziganshin <bulat.ziganshin at gmail.com>
>>
>> Hello Limestraėl,
>>>
>>> Saturday, May 15, 2010, 7:02:38 PM, you wrote:
>>>
>>> > But when I set my beat to tick every 60 times per second, the
>>> > position is well updated, but I clearly see that the display
>>> > dramatically slows down after a few seconds of execution. Too heavy
>>> rate for integrate?
>>>
>>> it may be due to lot of uncollected garbage that is result of lazy
>>> evaluation. profile program to check its GC times
>>>
>>>
>>> --
>>> Best regards,
>>>  Bulat                            mailto:Bulat.Ziganshin at gmail.com
>>>
>>>
>>
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>>
>>
>
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