Performance of tables slower than built in?

[Ola Fosheim Grøstad]

On Thursday, 23 May 2019 at 21:30:47 UTC, Alex wrote:
> I don't see how that can necessarily be faster. A LUT can give 
> full 64-bit precision with one operation. The CORDIC needs 
> iteration, at least 10 to be of any use. LUT's are precision 
> independent assuming the creation cost is not included.

It isn't, IEEE sin is typically not fast. Arm cpus let you run 
fewer iterations though for nonstandard floats.

> I have some code that uses sin, exp and a few other primitive 
> algebraic functions and in one case the code is extremely 
> slow(it uses exp).  I haven't done much testing of all this but 
> something just seems off somewhere.

Dont know about exp, but some operations are slow when you get 
too close to zero, so called denormal numbers.

> I guess there is no tool that can tell one exactly what is 
> happening to a piece of code in the cpu... basically an 
> instruction level profiler?

Vtune from Intel, not free... Afaik.