+ googol On Fri, Apr 3, 2009 at 1:43 PM, Mariano Kamp <[email protected]> wrote: > Romain, > > I am sure you are, but as with the Cupcake issue from the other thread > with Al, it is not transparent at all. The road map > (http://source.android.com/roadmap) doesn't contain much and doesn't seem up > to date. > > And don't get me started on the lack of transparency and predictability > regarding *all* things Android Market. > > Don't get me wrong though. This is not meant in any way as a personal > attack against you or in me laying the blame onto you. My point is that the > communications sucks and that your, Dianne's and JBQ's life would be easier > as well when someone offical from Google would put more effort into proper > communications. > > Cheers, > Mariano > > On Fri, Apr 3, 2009 at 10:29 AM, Romain Guy <[email protected]> wrote: >> >> We're aware of the shortcomings of the current garbage collector and >> believe me, it's one of the things we'd really love to see improved as >> soon as possible :) >> >> On Fri, Apr 3, 2009 at 2:04 AM, Mariano Kamp <[email protected]> >> wrote: >> > Anton, thanks. Very interesting. >> > On Fri, Apr 3, 2009 at 2:24 AM, Anton <[email protected]> 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 <[email protected]> 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 <[email protected]> >> >> > 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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, "[email protected]" >> >> > >> >> > > > > > > > > <[email protected]> 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 <[email protected]> >> >> > > > > > > > > > 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 <[email protected]> >> >> > > > > > > > > > > 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 < >> >> > > [email protected]> >> >> > > > > > > > > > > > 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 >> >> > > > > > > > > > > > > <[email protected]> >> >> > > wrote: >> >> > >> >> > > > > > > > > > > > > > I have a simple 2D physics >> >> > >> >> > ... >> >> > >> >> > read more » >> >> >> > >> > >> > > >> > >> >> >> >> -- >> Romain Guy >> Android framework engineer >> [email protected] >> >> Note: please don't send private questions to me, as I don't have time >> to provide private support. All such questions should be posted on >> public forums, where I and others can see and answer them >> >> > > > > >
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