Based on Chris Lomont's paper on the fast inverse square root C routine found in the source code from Quake III Arena i've implmented a square root c routine based on the method there described to derive the magic constant for an initial approximation and Newton-Raphson iterations for improvement of that value.
#TODO:
- Time testing on ARMv7 architecture
- Detailed tests against math.h sqrt
- Tests against SSE2 sqrt instructions
- Improve intial approximation
- Use uint32_t instead of unsigned
- Derive for double
- Compare with f * invsqrt(f)