Depending on the accuracy you need, and the code space available,
lookup tables can be your friend.  Do the hard math externally, and
just look up the answer.

I used LUTs when taking Shannon's entropy for 10 different analog and
digital sensors in a security sensor application.  MUCH faster than
computing it all from scratch.

Also, scale your variables.  Normally Shannon's entropy is expressed
as 0-1 in floating point, but expressing it as 0-255 in integer was
plenty good enough for my application, and much faster.

Do you NEED to know 1999 vs 20000 rpm?
--=20
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