Callstack

This call stack, captured from Google Play for one of my apps, shows what's fundamentally wrong with Android.

The app didn't even finish launching, and this is how deep the complexity runs?

backtrace:
  #00  pc 00000000000264f4  /system/lib/libharfbuzz_ng.so (hb_ot_layout_has_glyph_classes+28)
  #01  pc 0000000000049af0  /system/lib/libharfbuzz_ng.so (_hb_ot_shape+192)
  #02  pc 000000000001e008  /system/lib/libharfbuzz_ng.so (hb_shape_plan_execute+140)
  #03  pc 000000000001db30  /system/lib/libharfbuzz_ng.so (hb_shape+84)
  #04  pc 0000000000011b05  /system/lib/libminikin.so (minikin::Layout::doLayoutRun(unsigned short const*, unsigned int, unsigned int, unsigned int, bool, minikin::MinikinPaint const&, minikin::StartHyphenEdit, minikin::EndHyphenEdit)+3780)
  #05  pc 0000000000013991  /system/lib/libminikin.so (minikin::LayoutCacheKey::doLayout(minikin::Layout*, minikin::MinikinPaint const&) const+148)
  #06  pc 0000000000010bf5  /system/lib/libminikin.so (void minikin::LayoutCache::getOrCreate(minikin::U16StringPiece const&, minikin::Range const&, minikin::MinikinPaint const&, bool, minikin::StartHyphenEdit, minikin::EndHyphenEdit, minikin::LayoutAppendFunctor&)+468)
  #07  pc 0000000000010717  /system/lib/libminikin.so (minikin::Layout::doLayoutWord(unsigned short const*, unsigned int, unsigned int, unsigned int, bool, minikin::MinikinPaint const&, unsigned int, minikin::StartHyphenEdit, minikin::EndHyphenEdit, minikin::LayoutPieces const*, minikin::Layout*, float*, minikin::MinikinExtent*, minikin::MinikinRect*, minikin::LayoutPieces*)+234)
  #08  pc 000000000000fcd5  /system/lib/libminikin.so (minikin::Layout::doLayoutRunCached(minikin::U16StringPiece const&, minikin::Range const&, bool, minikin::MinikinPaint const&, unsigned int, minikin::StartHyphenEdit, minikin::EndHyphenEdit, minikin::LayoutPieces const*, minikin::Layout*, float*, minikin::MinikinExtent*, minikin::MinikinRect*, minikin::LayoutPieces*)+1160)
  #09  pc 0000000000010609  /system/lib/libminikin.so (minikin::Layout::measureText(minikin::U16StringPiece const&, minikin::Range const&, minikin::Bidi, minikin::MinikinPaint const&, minikin::StartHyphenEdit, minikin::EndHyphenEdit, float*, minikin::MinikinExtent*, minikin::LayoutPieces*)+1292)
  #10  pc 000000000022ca17  /system/lib/libhwui.so (android::MinikinUtils::measureText(android::Paint const*, minikin::Bidi, android::Typeface const*, unsigned short const*, unsigned int, unsigned int, unsigned int, float*)+82)
  #11  pc 00000000000e1cd5  /system/lib/libandroid_runtime.so (android::PaintGlue::getRunAdvance___CIIIIZI_F(_JNIEnv*, _jclass*, long long, _jcharArray*, int, int, int, int, unsigned char, int)+204)
  #12  pc 0000000000a4758b  /system/framework/arm/boot-framework.oat (android.graphics.Paint.nGetRunAdvance+178)
  #13  pc 0000000000a48e0d  /system/framework/arm/boot-framework.oat (android.graphics.Paint.getRunAdvance+172)
  #14  pc 0000000000a48cab  /system/framework/arm/boot-framework.oat (android.graphics.Paint.getRunAdvance+250)
  #15  pc 0000000001482e99  /system/framework/arm/boot-framework.oat (android.text.TextLine.getRunAdvance+128)
  #16  pc 0000000001483d89  /system/framework/arm/boot-framework.oat (android.text.TextLine.handleText+312)
  #17  pc 0000000001483367  /system/framework/arm/boot-framework.oat (android.text.TextLine.handleRun+566)
  #18  pc 0000000001484f49  /system/framework/arm/boot-framework.oat (android.text.TextLine.measure+216)
  #19  pc 0000000001485bcd  /system/framework/arm/boot-framework.oat (android.text.TextLine.metrics+44)
  #20  pc 00000000017ac2c9  /system/framework/arm/boot-framework.oat (android.text.BoringLayout.isBoring+384)
  #21  pc 0000000001af2d8f  /system/framework/arm/boot-framework.oat (android.widget.TextView.onMeasure+430)
  #22  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #23  pc 0000000001a7c3bb  /system/framework/arm/boot-framework.oat (android.view.ViewGroup.measureChildWithMargins+178)
  #24  pc 0000000001c900a1  /system/framework/arm/boot-framework.oat (android.widget.LinearLayout.measureChildBeforeLayout+64)
  #25  pc 0000000001c904ed  /system/framework/arm/boot-framework.oat (android.widget.LinearLayout.measureHorizontal+1060)
  #26  pc 0000000001c91f41  /system/framework/arm/boot-framework.oat (android.widget.LinearLayout.onMeasure+64)
  #27  pc 0000000001f4f553  /system/framework/arm/boot-framework.oat (com.android.internal.widget.ButtonBarLayout.onMeasure+226)
  #28  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #29  pc 0000000001d3747d  /system/framework/arm/boot-framework.oat (android.widget.ScrollView.measureChildWithMargins+228)
  #30  pc 0000000001c87141  /system/framework/arm/boot-framework.oat (android.widget.FrameLayout.onMeasure+296)
  #31  pc 0000000001d384f7  /system/framework/arm/boot-framework.oat (android.widget.ScrollView.onMeasure+46)
  #32  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #33  pc 0000000001f4eaf3  /system/framework/arm/boot-framework.oat (com.android.internal.widget.AlertDialogLayout.tryOnMeasure+434)
  #34  pc 0000000001f4f13f  /system/framework/arm/boot-framework.oat (com.android.internal.widget.AlertDialogLayout.onMeasure+46)
  #35  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #36  pc 0000000001a7c3bb  /system/framework/arm/boot-framework.oat (android.view.ViewGroup.measureChildWithMargins+178)
  #37  pc 0000000001c87141  /system/framework/arm/boot-framework.oat (android.widget.FrameLayout.onMeasure+296)
  #38  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #39  pc 0000000001a7c3bb  /system/framework/arm/boot-framework.oat (android.view.ViewGroup.measureChildWithMargins+178)
  #40  pc 0000000001c87141  /system/framework/arm/boot-framework.oat (android.widget.FrameLayout.onMeasure+296)
  #41  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #42  pc 0000000001a7c3bb  /system/framework/arm/boot-framework.oat (android.view.ViewGroup.measureChildWithMargins+178)
  #43  pc 0000000001c87141  /system/framework/arm/boot-framework.oat (android.widget.FrameLayout.onMeasure+296)
  #44  pc 0000000001d65865  /system/framework/arm/boot-framework.oat (com.android.internal.policy.DecorView.onMeasure+1252)
  #45  pc 000000000180ff23  /system/framework/arm/boot-framework.oat (android.view.View.measure+826)
  #46  pc 00000000018368f7  /system/framework/arm/boot-framework.oat (android.view.ViewRootImpl.performMeasure+246)
  #47  pc 00000000018353ed  /system/framework/arm/boot-framework.oat (android.view.ViewRootImpl.measureHierarchy+500)
  #48  pc 000000000183733b  /system/framework/arm/boot-framework.oat (android.view.ViewRootImpl.performTraversals+2330)
  #49  pc 000000000183dbb5  /system/framework/arm/boot-framework.oat (android.view.ViewRootImpl.doTraversal+188)
  #50  pc 0000000000d5e83d  /system/framework/arm/boot-framework.oat (android.content.ContextWrapper.getBasePackageName [DEDUPED]+52)
  #51  pc 0000000001515df7  /system/framework/arm/boot-framework.oat (android.view.Choreographer.doCallbacks+966)
  #52  pc 0000000001516675  /system/framework/arm/boot-framework.oat (android.view.Choreographer.doFrame+1396)
  #53  pc 00000000017d6413  /system/framework/arm/boot-framework.oat (android.view.Choreographer$FrameDisplayEventReceiver.run+66)
  #54  pc 000000000130e659  /system/framework/arm/boot-framework.oat (android.os.Handler.dispatchMessage+64)
  #55  pc 0000000001313e8b  /system/framework/arm/boot-framework.oat (android.os.Looper.loop+1162)
  #56  pc 0000000000c905d3  /system/framework/arm/boot-framework.oat (android.app.ActivityThread.main+674)
  #57  pc 0000000000417575  /system/lib/libart.so (art_quick_invoke_stub_internal+68)
  #58  pc 00000000003f125f  /system/lib/libart.so (art_quick_invoke_static_stub+222)
  #59  pc 00000000000a1043  /system/lib/libart.so (art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)+154)
  #60  pc 000000000035093d  /system/lib/libart.so (art::(anonymous namespace)::InvokeWithArgArray(art::ScopedObjectAccessAlreadyRunnable const&, art::ArtMethod*, art::(anonymous namespace)::ArgArray*, art::JValue*, char const*)+52)
  #61  pc 0000000000351d85  /system/lib/libart.so (art::InvokeMethod(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, _jobject*, _jobject*, unsigned int)+960)
  #62  pc 0000000000302b15  /system/lib/libart.so (art::Method_invoke(_JNIEnv*, _jobject*, _jobject*, _jobjectArray*)+40)
  #63  pc 00000000006ab577  /system/framework/arm/boot-core-oj.oat (java.lang.Class.getDeclaredMethodInternal [DEDUPED]+110)
  #64  pc 000000000165417b  /system/framework/arm/boot-framework.oat (com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run+114)
  #65  pc 000000000165da49  /system/framework/arm/boot-framework.oat (com.android.internal.os.ZygoteInit.main+2896)
  #66  pc 0000000000417575  /system/lib/libart.so (art_quick_invoke_stub_internal+68)
  #67  pc 00000000003f125f  /system/lib/libart.so (art_quick_invoke_static_stub+222)
  #68  pc 00000000000a1043  /system/lib/libart.so (art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)+154)
  #69  pc 000000000035093d  /system/lib/libart.so (art::(anonymous namespace)::InvokeWithArgArray(art::ScopedObjectAccessAlreadyRunnable const&, art::ArtMethod*, art::(anonymous namespace)::ArgArray*, art::JValue*, char const*)+52)
  #70  pc 0000000000350759  /system/lib/libart.so (art::InvokeWithVarArgs(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, _jmethodID*, std::__va_list)+304)
  #71  pc 000000000029493d  /system/lib/libart.so (art::JNI::CallStaticVoidMethodV(_JNIEnv*, _jclass*, _jmethodID*, std::__va_list)+476)
  #72  pc 000000000006d819  /system/lib/libandroid_runtime.so (_JNIEnv::CallStaticVoidMethod(_jclass*, _jmethodID*, ...)+28)
  #73  pc 000000000006f9cf  /system/lib/libandroid_runtime.so (android::AndroidRuntime::start(char const*, android::Vector const&, bool)+466)
  #74  pc 0000000000001b21  /system/bin/app_process32 (main+880)
  #75  pc 00000000000a2b3d  /system/lib/libc.so (__libc_init+48)
  #76  pc 000000000000176f  /system/bin/app_process32 (_start_main+46)
  #77  pc 0000000000019da9  /system/bin/linker (__dl__ZN6soinfoD1Ev+16)
  #78  pc 00000000007fea64  [stack:ff3b8000]

Unity

Two days ago, I started using the Unity3D game development tool. Interestingly, Unity3D is the most pervasive tool in the Game Dev industry... it is everywhere. I've been making games since 1982, but have never used it before.

I'm one of those dinosaurs keeping to the old way of doing things, and making my own game engines. Think of a manual 3-gear transmission Willys Jeep instead of heated seats, 7 cup-holder, navsat SUV.

So far, I like it better than I thought I would. In this blog article, I will collect some gotchas, insights, surprises that I will undoubtedly encounter.

1. Project loads are slow. Once inside the editor, make sure you stop "Playback" before editing anything... all edits during playback will be lost.

2. Unity uses degrees, not radians for angles.

3. You can only use const for compile-time constants. Not for run-time constants, like C and C++.

4. Unity physics is a wrapper over PhysX. Neither uses ERP and CFM like OpenDE and Bullet Physics do.

5. Unity debug output prints vectors with low precision. So (0.0, 0.3, 1.0) can actually be unit length!

6. My bicycle wheel would not spin faster than 7 radians per second, no matter how much torque I applied to it. It turns out that there is a rigid body property that caps it.

7. There is no include directive in the C# language. Instead, files that using the same namespace will automagically find each other's definitions.

8. Centre of mass and inertia tensor are automatically computed from the collision geometry! Beware of this: simulation results will be different just by changing collision geometry, unless you set c.o.m. and inertia explicitly.

9. Monobehaviour.Awake() is called in random order for the Gameobjects. Ugh.

Sprinkle, Sprinkle, Little Star.

I released a new software application. It is named "Sprinkle, Sprinkle, Little Star" and is available for free for Windows and Linux.

It is a 2D simulation of Gravity acting on a galaxy of stars. It is completely interactive, and you can paint your own galaxy onto a grid, and see the galaxy evolve under Newton's law for gravity.

I recorded a video of myself with a play-though.

I started it during the holiday break, and had fun implementing it. The so called N-Body problem is pretty hard to solve interactively for large numbers of stars, because of its O(N*N) nature: Each star is influenced by each other stars. This means calculating 100M distances if you have 10,000 stars. To do it efficiently, I had to aggregate stars at larger distances. In addition to this, I vectorized my code with AVX intrinsics, that calculates 8 forces in a single go using SIMD. Because my compiler did such a bad job on the scalar code, the speed up was even better than 8, I saw a x18 increase in framerate (which also included rendering, so the computation speed up was even a little more than 18x.) Below is the spatial structure I use to aggregate stars at large distances.