[SOLVED] Vectorized Trig functions in C?

Issue

I'm looking to calculate highly parallelized trig functions (in block of like 1024), and I'd like to take advantage of at least some of the parallelism that modern architectures have.

When I compile a block

for(int i=0; i<SIZE; i++) {
   arr[i]=sin((float)i/1024);
}

GCC won't vectorize it, and says

not vectorized: relevant stmt not supported: D.3068_39 = __builtin_sinf (D.3069_38);

Which makes sense to me. However, I'm wondering if there's a library to do parallel trig computations.

With just a simple taylor series up the 11th order, GCC will vectorize all the loops, and I'm getting speeds over twice as fast as a naive sin loop (with bit-exact answers, or with 9th order series, only a single bit off for the last two out of 1600 values, for a >3x speedup). I'm sure someone has encountered a problem like this before, but when I google, I find no mentions of any libraries or the like.

A. Is there something existing already?
B. If not, advice for optimizing parallel trig functions?

EDIT: I found the following library called "SLEEF": http://shibatch.sourceforge.net/ which is described in this paper and uses SIMD instructions to calculate several elementary functions. It uses SSE and AVX specific code, but I don't think it will be hard to turn it into standard C loops.

Solution

My answer was to create my own library to do exactly this called vectrig: https://github.com/jeremysalwen/vectrig

Answered By - Jeremy Salwen

Answer Checked By - David Goodson (WPSolving Volunteer)