Faster asin() was hiding in plain sight
1–10 of 140 posts
Re: Faster asin() was hiding in plain sight
#2[deleted]
Re: Faster asin() was hiding in plain sight
#3Ideal HN content, thanks!
Re: Faster asin() was hiding in plain sight
#4> Nobody likes throwing away work they've done
I like throwing away work I've done. Frees up my mental capacity for other work to throw away.
Re: Faster asin() was hiding in plain sight
#5[flagged]
Re: Faster asin() was hiding in plain sight
#6We love to leave faster functions languishing in library code. The basis for Q3A’s fast inverse square root had been sitting in fdlibm since 1986, on the net since 1993: https://www.netlib.org/fdlibm/e_sqrt.c
Re: Faster asin() was hiding in plain sight
#7Did some quick calculations, and at this precision, it seems a table lookup might be able to fit in the L1 cache depending on the CPU model.
Re: Faster asin() was hiding in plain sight
#8Isn't the faster approach SIMD [edit: or GPU]? A 1.05x to 1.90x speedup is great. A 16x speedup is better!
They could be orthogonal improvements, but if I were prioritizing, I'd go for SIMD first.
I searched for asin on Intel's intrinsics guide. They have a AVX-512 instrinsic `_mm512_asin_ps` but it says "sequence" rather than single-instruction. Presumably the actual sequence they use is in some header file somewhere, but I don't know off-hand where to look, so I don't know how it compares to a SIMDified version of `fast_asin_cg`.
https://www.intel.com/content/www/us/en/docs/intrinsics-guid...
Re: Faster asin() was hiding in plain sight
#9Did some quick calculations, and at this precision, it seems a table lookup might be able to fit in the L1 cache depending on the CPU model.
Microbenchmarks. A LUT will win many of them but you pessimise the rest of the code. So unless a significant (read: 20+%) portion of your code goes into the LUT, there isn't that much point to bother. For almost any pure calculation without I/O, it's better to do the arithmetic than to do memory access.
Re: Faster asin() was hiding in plain sight
#10Isn't the faster approach SIMD [edit: or GPU]? A 1.05x to 1.90x speedup is great. A 16x speedup is better! They could be orthogonal improvements, but if I were prioritizing, I'd go for SIMD first. I searched for asin on Intel's intrinsics guide. They have a AVX-512 instrinsic `_mm512_asin_ps` but it says "sequence" rather than single-instruction. Presumably the actual sequence they use is in some header file somewher…
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