[kstrauser]

> The 4% improvement doesn't seem like it's worth the effort.

People have gotten PhDs for smaller optimizations. I know. I've worked with them.

> instructions like division and square root are roughly equal to trig functions in cycle count on modern CPUs.

What's the x86-64 opcode for arcsin?

[glitchc]

> What's the x86-64 opcode for arcsin?

Not required. ATAN and SQRTS(S|D) are sufficient, the half-angle approach in the article is the recommended way.

> People have gotten PhDs for smaller optimizations. I know. I've worked with them.

I understand the can, not sure about the should. Not trying to be snarky, we just seem to be producing PhDs with the slimmest of justifications. The bar needs to be higher.

[kstrauser]

> I understand the can, not sure about the should. Not trying to be snarky, we just seem to be producing PhDs with the slimmest of justifications. The bar needs to be higher.

I couldn't disagree more. Sure, making a 4% faster asin isn't going to change the world, but if it makes all callers a teensy bit faster, multiplied by the number of callers using it, then it adds up. Imagine the savings for a hyperscaler if they managed to made a more common instruction 4% faster.

[adrian_b]

Presumably the poster meant polynomial approximations of trigonometric functions not instructions for trigonometric functions, which are missing in most CPUs, though many GPUs have such instructions.

x86-64 had instructions for the exponential and logarithmic functions in Xeon Phi, but those instructions have been removed in Skylake Server and the later Intel or AMD CPUs with AVX-512 support.

However, instructions for trigonometric functions have no longer been added after Intel 80387, and those of 8087 and 80387 are deprecated.