The real test would be to decompile an ESP32 binary and check what
instruction its really using. If its using the instructions from
https://0x04.net/~mwk/doc/xtensa.pdf what require the FPU option then it
has to actually be using the FPU unless xtensa is not being true full of
their core having an FPU.

I might do some research into using Assembly to implement functions that do
use the FPU instructions if it turns out the compiler if not really using
them. (Which could be the case.)

William KD9KCK


On Thu, Feb 6, 2020 at 12:30 PM Dana Myers <[email protected]> wrote:

> On 2/6/2020 6:23 AM, Bill Gaylord wrote:
> > Personally it seems pretty fast only like a max of 9 us for most ops on
> floats (doubles are a different story.) It can be as low
> > as almost 1 us or as high as 55 us depending on operation.
>
> FPUs in the ESP32 and Cortex-M4F are all single-precision (float); if you
> ask for
> double-precision, you don't use the FPU and you get to wait.
>
> Also, 9uS is *terrible*, I'll bet that's a transcendental operation
> running in
> software and not using the FPU.
>
> Cheers,
> Dana  K6JQ
>
>
>
>
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