Warp <war### [at] tagpovrayorg> wrote:
>   You are telling me that calculating trigonometric functions on 64-bit
> floating point values in software is faster than using the FPU?
>
>   I'm not sure that would make too much sense. It would mean that they
> would *deliberately* make the FPU calculate those functions in a less
> efficient way than you could do with the CPU.

.... or deliberately not spending so much effort on improving these functons,
while the rest of the CPU is constantly overhauled to make it faster.

In the good old days, when CPU manufacturers still published information like
the machine cycles per instruction, it was not too uncommon for a few
instructions to actually take more cycles on newer CPUs.

Actually, the complexity of the x87 FPU may make it harder to optimize than
other parts of the CPU, and there may also be issues regarding the
interoperation with other speedup mechanisms, like jump prediction or
what-have-you.

So while I still doubt whether SSE2 based software can achieve the same speed as
the x87 FPU, it is not *too* far-fetched either. And maybe there's even room for
parallelization of some computations in transcendent functions that I don't see
right now.


(BTW, did you know that during a single clock cycle of your CPU, a light ray
actually travels no more than about 10 cm? And electrons are typically still a
deal slower.)

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