Fast sine/cosine for ARMv7+NEON: looking for testers…

Question

Could somebody with access to an iPhone 3GS or a Pandora please test the following assembly routine I just wrote? It is supposed to compute sines and cosines really really fast on the NEON vector FPU. I know it compiles fine, but without adequate hardware I can't test it. If you could just compute a few sines and cosines and compare the results with those of sinf() and cosf() it would really help. Thanks! ``` #include <math.h> /// Computes the sine and cosine of two angles /// in: angles = Two angles, expressed in radians, in the [-PI,PI] range. /// out: results = vector containing [sin(angles[0]),cos(angles[0]),sin(angles[1]),cos(angles[1])] static inline void vsincos(const float angles[2], float results[4]) { static const float constants[] = { /* q1 */ 0, M_PI_2, 0, M_PI_2, /* q2 */ M_PI, M_PI, M_PI, M_PI, /* q3 */ 4.f/M_PI, 4.f/M_PI, 4.f/M_PI, 4.f/M_PI, /* q4 */ -4.f/(M_PI*M_PI), -4.f/(M_PI*M_PI), -4.f/(M_PI*M_PI), -4.f/(M_PI*M_PI), /* q5 */ 2.f, 2.f, 2.f, 2.f, /* q6 */ .225f, .225…

Accepted Answer

Just tested it on my beagleboard.. As said in the comments: Same CPU.

Your code is roughly 15 times faster than the clib.. Well done!

I've measured 82 cycles for each call of your implementation and 1260 for the four c-lib calls. Note that I've compiled with soft-float ABI and my OMAP3 is early silicon, so each call to the the c-lib version has a NEON stall of at least 40 cycles.

I've zipped together the results..

http://torus.untergrund.net/code/sincos.zip

The performance-counter stuff will most likely not work on the iphone.

Hope that's what you've been looking for.

Fast sine/cosine for ARMv7+NEON: looking for testers…

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