Speed of math function atan: comparison D and C++

[Era Scarecrow]

On Monday, 5 March 2018 at 05:40:09 UTC, rikki cattermole wrote:
> atan should work out to only be a few instructions (inline 
> assembly) from what I've looked at in the source.
>
> Also you should post the code you used for each.

  Should be 3-4 instructions. Load input to the FPU (Optional? 
Depends on if it already has the value loaded), Atan, Fwait 
(optional?), Retrieve value.

  Off hand that i remember, FPU instructions run in their own 
separated space and should more or less take up only a few cycles 
by themselves to run (and also run in parallel to the CPU code).

  At which point if the code is running half the speed of C++'s, 
that means probably bad optimization elsewhere, or even the 
control settings for the FPU.

  I really haven't looked that in depth to the FPU stuff since 
about 2000...