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

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

On Sat, May 15, 2010 at 8:42 AM, Limestraël 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

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@gmail.com

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