Anton, thanks. Very interesting. On Fri, Apr 3, 2009 at 2:24 AM, Anton <socialhac...@gmail.com> wrote:
> > Check out > http://android-developers.blogspot.com/2009/02/track-memory-allocations.html > > Romain Guy points out in this post that the android garbage > collector cannot optimize small short lived objects. These are > exactly the sort of objects that could be created in a physics engine > when it needs to generate dynamic collision constraints. A good > solution in this case is to use a pool of constraint objects because > they are all going to be the same size/object. The best solution in > my mind would be for the compiler to do escape analysis on the objects > and stack allocate them when it sees that they will never escape the > function. I have been told that the Java byte code can't reference an > object on the stack. It's possible that the Dalvik byte code can, I > don't know. > > I don't have a reference for this, but I assume that Dalvik's > inability to optimize small short lived object comes from the fact > that it uses a mark and sweep GC. On all of my profiling, I see the > GC take at least 100ms to run. For a game that means you miss from > three to 10 frames of animation and it makes for a pretty noticeable > hick up. And I don't think it's my application that is causing the > garbage collector to fire. Unless the OpenGL ES calls do some memory > allocation, which is entirely possible. I realize that any background > task could move to the run queue and take some time away from my > engine, it just happens to be the garbage collector most of the > time. :) > > So the result is that the Garbage collector is problematic for me > in two ways. First, it's not optimized to deal with the sort of small > objects that tend to make for good encapsulations of mathematical > types (like Fixed point number classes or Vector or Matrix classes). > And secondly it takes a long time to run when it does garbage collect, > resulting in dropped frames. > > -Anton > > On Apr 2, 3:32 pm, Mariano Kamp <mariano.k...@gmail.com> wrote: > > It's maybe a bit off topic, but how do you know that Android's gc is > > rudimentary? Have you got a link handy? > > I only found this: > http://developer.android.com/guide/practices/design/performance.html > > > > On Thu, Apr 2, 2009 at 11:59 PM, Anton <socialhac...@gmail.com> wrote: > > > > > Shaun, thanks for checking it out. Yah, I agree that the real > > > complexity of a physics engine comes from joints and contact > > > constraints. The constraints in my demo are simple minimum distance > > > constraints. I have a 2D rigid body physics engine that I'm thinking > > > more and more about porting over to Android as well. This demo was > > > more of a calibration for myself to see how much computation I can do, > > > and what optimizations lead to the largest improvements. I'll > > > probably turn it into a fun toy for the Market and then look into > > > rewriting my rigid body engine for Android. > > > > > Reading through Simpull I noticed that you allocate a new Vector3f > > > in your Verlet update routine. I think that will be a killer on the > > > Android platform because of it's rudimentary garbage collector and > > > limited RAM. My solution was to allocate an array of fixed point > > > numbers, four per ball. Effectively a vector pool that didn't require > > > any management because the number of balls never changed. > > > > > On Apr 2, 6:31 am, shaun <shashepp...@gmail.com> wrote: > > > > I took a look at Anton's demo on a G1 device, and I was glad to see > > > > the integration of accelerometer as it really added value. I assume > > > > the calculations for collision detection and response are fairly > > > > basic, which allows for that performance. > > > > > > Simpull will also provide good performance for a scene of that nature > > > > (all verlet, no joints). At least I believe it will. The point > where > > > > simpull becomes slow is when a more complex scene is in play with 10s > > > > of objects with many joints connecting some of them. Since the > engine > > > > is all verlet and no rigid body dynamics, joints are one way to > > > > acheive a similar result, but with a very bad performance hit due to > > > > all the new temporary objects and new calculations. > > > > > > I would be super impressed to see a demo like Anton's with rigid body > > > > dynamics involved with at least some rectangles, if not other > polygons > > > > and perhaps a joint or two. That is where the performance degrades > > > > quickly in my experience. > > > > > > On Apr 1, 2:45 pm, mscwd01 <mscw...@gmail.com> wrote: > > > > > > > Thanks Lajos for pointing APE out, I hadn't heard of it until now. > > > > > > > Unfortunately your link to your Android port is broken, can you > mend > > > > > it as I dont fancy spending another hour porting another library to > > > > > Android :D > > > > > > > Thanks > > > > > > > On Mar 31, 9:50 pm, lkelemen <tridc...@gmail.com> wrote: > > > > > > > > Hello everyone, > > > > > > > > I was also disappointed with jbox2d's performance so I checked > APE > > > > > > (Actionscript Physics Engine) fromhttp://www.cove.org/ape/. > > > > > > It was converted to java (http://www.cove.org/ape/java_ape.zip) > so I > > > > > > started to convert the java version to Android. > > > > > > > > The performance is quite OK for 10-20 objects at the first start > of > > > > > > the app but if you exit with the back key and restart it form the > > > > > > installed copy > > > > > > (either in the emulator or on the dev phone) then it gets slower > and > > > > > > slower with each start. If you restart it from the emulator (by > > > > > > reinstalling it) then it is faster again. > > > > > > Neither the pressed keys are not working (probably it is because > of > > > my > > > > > > poor Android programming knowledge). > > > > > > > > Here is a zipped Android project of it. Please experiment with it > and > > > > > > send results to here i.e. is it slow for you also after > re-re-re-.. > > > > > > staring?www.kotiposti.net/lkelemen/android/testape2d.zip > > > > > > > > thanks > > > > > > Lajos Kelemen > > > > > > > > On Mar 31, 9:26 pm, shaun <shashepp...@gmail.com> wrote: > > > > > > > > > I started going down the path of Object pooling. It seemed the > > > only > > > > > > > solution when taking an existing engine and making work on a > > > resource > > > > > > > constrained system like Android on a phone. Determining the > > > strategy > > > > > > > for returning objects to the pool proved quite tough for me. I > > > have > > > > > > > no doubt there are some experts on embedded systems programming > > > with > > > > > > > tons of experience with object pooling. We just would be too > lucky > > > if > > > > > > > that person(s) was also experienced with Java, physics engines > and > > > had > > > > > > > a passion for open source and games! Is that too much to ask? > > > LOL!! > > > > > > > > > On Mar 31, 12:17 pm, mscwd01 <mscw...@gmail.com> wrote: > > > > > > > > > > Thanks for your feedback Shaun, I too unfortunately think a > > > bespoke > > > > > > > > engine will need to be written for Android, which is a real > pity > > > as > > > > > > > > the iPhone has several physics engines which can easily > handle > > > > > > > > hundreds of objects. > > > > > > > > > > Having said that Anton (2nd reply) has said he has an engine > > > running, > > > > > > > > it would be nice to see a demo of this if that'd be possible? > > > > > > > > > > Clark, i'd definately host any .apk's on my own site, I > wouldn't > > > put > > > > > > > > it on the marketplace if it wasn't a "finished" app - do > people > > > > > > > > actually do that?! > > > > > > > > > > I think i'll stay away from developing games with physics for > the > > > time > > > > > > > > being and concentrate on something else, I cant see it being > > > feasible > > > > > > > > to include it any time soon which is a real pity. > > > > > > > > > > On Mar 31, 3:28 pm, shaun <shashepp...@gmail.com> wrote: > > > > > > > > > > > I am the author ofsimpull. > > > > > > > > > > > Sorry guys for the demo being out of whack forSimpullto the > > > Core. > > > > > > > > > The version of PulpCore that I integratedsimpullwith did > not > > > support > > > > > > > > > Chrome, but you should be able to see it in IE, FF Safari. > It > > > is nice > > > > > > > > > to take a look at that demo to get a feel for what the > engine > > > is > > > > > > > > > capable of, but the performance does not translate over to > the > > > fixed > > > > > > > > > point branch/version ofsimpullwhen running on Android. > > > > > > > > > > > I ran tests on both the emulator and the actual device and > > > there was a > > > > > > > > > significant increase in performance because of the fixed > point > > > > > > > > > implementation, but I got very frustrated that it still did > not > > > > > > > > > support the amount of objects in a scene that I considered > good > > > for a > > > > > > > > > physics-based game. It seemed to handle ~10 objects moving > and > > > > > > > > > colliding OK. It has been a while since I was playing with > it, > > > so I > > > > > > > > > do not really remember the exact number of objects or the > frame > > > rate. > > > > > > > > > I mostly remember being upset with it. > > > > > > > > > > > I am leaving the physics ideas for games out of the picture > > > when > > > > > > > > > thinking Android for now. Someone would have to write a > ground > > > up > > > > > > > > > engine with all the performance and memory concerns of > Android > > > in > > > > > > > > > mind, which was not the case withSimpull.....I created it > for > > > > > > > > > applets, then thought to port over to fixed-point for > Android. > > > It > > > > > > > > > works well with small scenes, but certainly not the staple > > > engine to > > > > > > > > > use in my opinion. > > > > > > > > > > > Also, Phys2D will not run worth a damn on Android. I tried > it > > > and I > > > > > > > > > even went through some heavy performance tuning. Garbage > > > collection > > > > > > > > > is the major issue even after all I did. I seriously doubt > > > JBox2D > > > > > > > > > will run well either. I'll stick to what I said earlier, a > > > ground-up > > > > > > > > > solution by someone smarter than me is probably required. > > > > > > > > > > > On Mar 31, 9:49 am, "admin.androidsl...@googlemail.com" > > > > > > > > > > > <admin.androidsl...@googlemail.com> wrote: > > > > > > > > > > Not tried but if you can provide us with some example > source > > > code or > > > > > > > > > > put something on the market, I'm sure we could take a > look. > > > > > > > > > > > > G1 performance is significantly faster than emulator, but > > > there are > > > > > > > > > > limitations. > > > > > > > > > > > > Particularly with garbage collection and memory > allocation on > > > code > > > > > > > > > > that gets run continuously in loops, so I don't know how > > > optimised > > > > > > > > > > these physics engines are for this purpose. > > > > > > > > > > > > Would be interesting to find out though. > > > > > > > > > > > > On Mar 31, 12:52 pm, mscwd01 <mscw...@gmail.com> wrote: > > > > > > > > > > > > > Oh I forgot to re-ask... > > > > > > > > > > > > > "Has anyone tested Phys2D or JBox2D on an actual device > to > > > see if they > > > > > > > > > > > run better than on the emulator? > > > > > > > > > > > > > I have a feeling the performance will better on a G1 > than > > > the emulator > > > > > > > > > > > for some reason! > > > > > > > > > > > > > On Mar 31, 12:51 pm, mscwd01 <mscw...@gmail.com> > wrote: > > > > > > > > > > > > > > I did take a look atSimpull, however the demo > application > > > failed to > > > > > > > > > > > > run as it relied on some library which wasn't > supplied or > > > referenced > > > > > > > > > > > > to - I just got annoyed after spending two days > failing > > > to get Phys2D > > > > > > > > > > > > and JBox2D to work in Android and didn't bother > trying to > > > work out the > > > > > > > > > > > > problems! > > > > > > > > > > > > > > I might give it another look though... > > > > > > > > > > > > > > On Mar 30, 10:41 pm, Streets Of Boston < > > > flyingdutc...@gmail.com> > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > I wonder how well this one works on Android: > > > > > > > > > > > > > > > http://code.google.com/p/simpull/ > > > > > > > > > > > > > > > -- Anton Spaans > > > > > > > > > > > > > > > On Mar 30, 4:58 pm, Anton <socialhac...@gmail.com> > > > wrote: > > > > > > > > > > > > > > > > I have a simple 2D physics > > > > ... > > > > read more ยป > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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