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Multi threaded problem.

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Started 7 years ago by humble
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humble

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humble

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Hello Sparrows. I have more multi threaded problems. I have a second thread with a callback function, passing midi event data. This function calls a few sparrow side functions. Works great. However, when the load of incoming data is high the SPTouch is cut out, which would be fine if it happened only while processing data, but it never comes back.

The SPEnterFrame is called like normal and everything continuous running, but no touch events. Has anyone seen this before? Help, idea or guidance would be most appreciated…

Thanks

ERik

Posted 7 years ago #
Daniel

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Daniel

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Hm ... are you using SPPoint, SPMatrix or SPRectangle in the other thread? Perhaps it's a problem with object pooling, as that's not thread-safe (I think).
But that's just a guess!

Posted 7 years ago #
humble

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humble

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Ehrm, not directly. But when not not having an auto release pool I am sure I saw an sppoint in there. Is this used by other classes, like spquad maybe or the touch position thingy. Hmmm, I have to look at that. Cheers Daniel.

ERik

Posted 7 years ago #
humble

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humble

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Yep, it is leaking all those classes, SPPoint, SPMatrix and SPRectangle. Not that I use them, but I am guessing the internals of sparrow is. Does this mean that sparrow isn't thread safe perhaps?

ERik

Posted 7 years ago #
Daniel

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Daniel

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In that case, you could deactivate object pooling for those classes. Simply add the following preprocessor macro in your project/target settings:

DISABLE_MEMORY_POOLING

As Sparrow uses those classes internally during rendering, it will get a little slower -- but it's not that critical, you can safely try that out. The object pooling is definitely not thread safe, yes!

Posted 7 years ago #
humble

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humble

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Ok, thanks. I will try that. Your the best Daniel.

ERik

Posted 7 years ago #
humble

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humble

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Hmmm.. I am getting errors in the SPPoolObject then...

Posted 7 years ago #
Daniel

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Daniel

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Hm, which error are you getting?

Posted 7 years ago #
humble

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humble

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@class SPPoolObject;

! 'struct SPPoolObject' has a previous decalration as 'struct SPPoolObject' 2

typedef NSObject SPPoolObject;

! Conflicting declaration 'typedef struct NSObject SPPoolObject' 2

@interface SPPoint : SpPoolObject <NSCopying>

! Cannot find interface declaration for 'SPPoolObject', superclass of SPPoint 2

…and then the same for SPRectangle and SPMatrix. Thanks.

ERik

Posted 7 years ago #
Daniel

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Daniel

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Hm, very odd. I just tried it with Xcode 4.1 and the Demo project. In the build settings of Sparrow (!), I searched for "Preprocessor Macros" and added DISABLE_MEMORY_POOLING right beside the DEBUG macro. (I used the "Combined" setting just to be sure it's not in the wrong layer.) Then I did a "clean", and rebuilt the whole project.

And it worked just fine!

Is there perhaps anything you've done differently on your system?

Posted 7 years ago #
humble

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humble

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Yeah, I probably added it in the wrong place. I'll try it again. Cheers Daniel.

ERik

Posted 7 years ago #
humble

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humble

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Nääääääh, I can't get it to work. Ah, well. Still using good old Xcode 3.2.5.

ERik

Posted 7 years ago #
paul

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paul

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What I do for this problem is to edit +poolInfo to return a pointer to an SPPoolInfo struct that is specific to each thread. You can wrap their addresses in NSValue's and store them in an NSDictionary. Then you can return the correct pool based on [[NSThread currentThread] name].

I know exactly how many threads will be running at any one time and so can guarantee that each pool will be accessed by only one thread at a time. If you want to reassure yourself that multiple threads aren't accessing the same pool concurrently, you can distribute the thread keys from a central repository and throw an exception if a key is requested that is already in use by another thread.

The only downside is that you need to pre-define how many pools you want and what their keys will be. You could use a mutable dictionary, but then you'd need to guard access to it which I suspect would cancel any speed benefit the pool was offering in the first place (and maybe come at a large penalty).

Edited:

Removed the last line that made no sense

Posted 7 years ago #
humble

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humble

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Thanks Paul. I was really looking at this as a short cut to not having to redesign some old code, just now. It sounds interesting, but a bit to complicated, for now.

If only I could stop finding bugs after release, and not before.

ERik

Posted 7 years ago #
paul

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paul

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OK. If you do decide to do something like it, just remember to only purge from the main thread and only if no other threads are running.

Posted 7 years ago #
humble

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humble

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Coolio Paul. I think I will aim for an audio buffer player instead of sparrows sound channel, which is more suited for what I need, and I know it works with one of my other apps.

Cheers for the help. It is very much appreciated.

ERik

Posted 7 years ago #
Daniel

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Daniel

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Paul, that's a good idea, having different pools per thread. I'll think about adding something like that, at least optionally.

ERik, sorry that my preprocessor macro does not work for you! That's really very odd. I know I tested this with Xcode 3 before, and I don't know why it should suddenly stop working (I haven't touched that code for a long time).

If all else fails, a simple way to do it would be to just have SPPoint, SPRectangle and SPMatrix inherit from NSObject -- you could do that manually in your Sparrow copy.

Posted 7 years ago #
paul

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paul

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The preprocessor macro works for me in Xcode 3.2.5

Posted 7 years ago #
paul

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paul

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Daniel, I would definitely try to profile the benefit before spending time on a feature like that. I don't really know how much overhead there is in my method, but I suspect I am gaining very little. There's just something about the idea of pooling that is very appealing to me. Or maybe there's something about the perceived waste in not pooling that annoys me

Posted 7 years ago #
Daniel

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Daniel

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Yes, Paul, that is something that has to be profiled well -- you're right! I guess this might have performance implications, and in that case, we should find out if it's faster to turn off pooling, or to add that thread-split. If it's worth it, we could add another preprocessor macro like "THREADSAFE_MEMORY_POOLING". =)

Posted 7 years ago #
humble

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humble

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Oooh, tell me Paul. Where are you adding it exactly? I must be adding it in the wrong place. Step by step please for the stupid...

Thanks.

ERik

Posted 7 years ago #
paul

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paul

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Sure. Open up the Sparrow framework's project in Xcode (sparrow/src/Sparrow.xcodeproj). Then go to Project > Edit Project Settings. In my case the configuration is set to Debug (but you'd need to repeat this for Release at some point). Under the Build tab, search for "preprocessor". Under the "GCC 4.2 Processing" section you will see "Preprocessor Macros". It will likely have "DEBUG" already added. When you double-click on the cell with "DEBUG" in it a dialog box will pop up. Within this dialog box, click and hover over the word "DEBUG" to make it editable. Add a space after the word DEBUG and paste in DISABLE_MEMORY_POOLING. Now you can exit project settings.

Then I cleaned all targets and rebuilt the Sparrow framework. Then I switched to my game project and cleaned and rebuilt. You can set breakpoints to verify that the pooling code is no longer running.

Posted 7 years ago #
humble

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humble

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You are a star Paul.

ERik

Posted 7 years ago #
humble

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humble

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I don't know, it doesn't seem to do anything. Thanks though guys for the help. I think I'm going to have to live with the bug...

ERik

Posted 7 years ago #
paul

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paul

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Are you sure that you are linking to the same Sparrow source that you edited and re-built? Try to set a breakpoint in SPView.m of the Sparrow project and see if it halts on execution of your game.

Posted 7 years ago #
paul

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paul

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Also, are you saying it doesn't work because your original bug still exists, or because the pooling code is still being executed?

If it's the latter, Daniel mentioned this solution earlier:

"If all else fails, a simple way to do it would be to just have SPPoint, SPRectangle and SPMatrix inherit from NSObject -- you could do that manually in your Sparrow copy."

If it's the former, it's possible that this is not the source of your problem (or not the only source).

Posted 7 years ago #
humble

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humble

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I am not sure what I am saying really. The bug is still there. Disabling pooling, then in my mind wrapping the code in SP_CREATE_POOL(pool); shouldn't be needed right?! Doing that though I still see it leaking. Maybe I have it wrong though.

I am definitely changing the correct one as I open the sparrow project from my app project, can not be the wrong one then, I hope.

A want to avoid changing the sparrow code really but I might try that tomorrow.

But as you said Paul. This might not even be the source of the problem. I am using the same midi code for another project, which is not calling any sparrow code, and that works fine. So, it feels like it might be.

Thanks for all the help Paul, it is much appreciated.

ERik

Posted 7 years ago #
paul

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paul

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You'll still need the NSAutoreleasePool wrapping your thread otherwise you will leak any autoreleased objects created within it. But Sparrow goes beyond that and tries to recycle simple objects that are used regularly. However, the linked list that maintains these recycled objects is not thread safe. So theoretically, you could build a texture on another thread and "checkout" one of these recycled objects. But halfway through checkout, another thread checks it out too. Then you initialise it and begin to build your object, only to have the other thread memset its frame to 0 and redefine it. That might explain why your touches aren't registering - because their bounds/transform have been altered.

The simplest solution seems to be to disable Sparrow's internal pooling. And if the project settings don't work for you, then Daniel's other solution should be very easy to implement.

"If all else fails, a simple way to do it would be to just have SPPoint, SPRectangle and SPMatrix inherit from NSObject -- you could do that manually in your Sparrow copy."

Posted 7 years ago #
humble

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humble

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I might do the inherit thing next. That seems easiest. Cheers Paul.

ERik

Posted 7 years ago #
humble

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humble

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Yey, 30 posts and a lot of moaning, we are finally thread safe. Thank you so much Daniel and Paul. I will send you some promo codes. It is not much but...

ERik

Posted 7 years ago #

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