This project provides a build framework for TomsFastMath on Android.
Notes / TODO:
To use the faster ARM inline assembly, TFM_ARM must be defined at compile time. Unfortunately, is
incompatible with the armeabi build target because some of the instructions are not supported. The
Android SDK defines a few variables which may help with detection:
when compiled for armeabi-v7a:
__thumb2__
__ARM_ARCH_7A__
when compiled for armeabi:
__SOFTFP__
For now, the armeabi target will use the unoptimized C code. TFM_ARM is conditionally defined
for the armeabi-v7a target.
Build instructions:
(1) Clone this git repository to your project's JNI directory, naming the directory "tfm".
(2) Modify your JNI root's Android.mk and Application.mk using the files in this directory as a model.
(3) Run ndk-build (available from the Android NDK); see Gingerbread's NDK docs for more.
Known bugs / issues:
* armeabi builds are known to produce binary code that is over three times larger than armeabi-v7a.
This is probably due to either a bug in the Android NDK or limitations of the Thumb16 instruction set.
* NEON support can't really be turned on, because not all armeabi-v7a boards support it.
After some trials, it appears that gcc can auto-vectorize some loops when NEON support is enabled
and this leads to a performance increase. But doing so will cause the code to crash on phones
where NEON isn't supported...
