Warp <war### [at] tagpovrayorg> wrote:
>   In fact, the opcode which calculates the base-2 logarithm is given a
> factor. That factor is, rather obviously, the logarithm of the real base
> you want it to calculate. So you get, in fact, a logarithm in *any* base
> with one single opcode.

Hm.. I confess I didn't have such a close look at the instructions.

>   Btw, another advantage of using the FPU rather than calculating in
> software is that you could, at least in theory, have the FPU calculating
> your operation while the CPU does other (non-FPU) operations at the same
> time. I don't know if any compiler is able to opimize like this, though.

I guess most compilers do this. The x87 FPU has always been working in parallel
to the CPU, so the compiler architects had quite some years to figure out how
to achieve this.

>   (Of course the same is probably true of the SSE unit as well.)

Yup. But it will require more help from the CPU when doing complex tasks like
computing transcendental stuff, which will place some limitation on what you
can do at the same time.

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