exponent math

[Stump]

Greetings all
Is it at all possible to calculate the following...
answer= ((a+b)^1.15) using pbp?

(sum of a+b to the power of 1.15)

chip used is 18F6720
Thank you
Ron

[kenif]

Me too.

Bit late (15 years), but the same problem. I need to generate an exponential decay and PBP has no ^/exp function.

There are several ways to do this, but none of them are particularly quick, which is also a complaint of most built-in exp functions. I think, when we get this right, the fastest answer is a lookup table/array approach.

https://nic.schraudolph.org/bib2html/b2hd-Schraudolph99.html

https://codingforspeed.com/using-faster-exponential-approximation/

This doesn't seem too difficult so will try implementing this.

double exp1(double x) {
x = 1.0 + x / 256.0;
x *= x; x *= x; x *= x; x *= x;
x *= x; x *= x; x *= x; x *= x;
return x;
}

[mpgmike]

The line:


x = 1.0 + x / 256.0;

casts it as floating point. If you haven't used floating point math, you have your research cut out for you.

[pedja089]

Just create lookup table, with linear interpolation.
I found it to be simplest and fastest way.
I successfully created this function https://en.wikipedia.org/wiki/Mean_kinetic_temperature (second function)
Using only 2 lookup tables, and linear approximation.
Mel posted years ago example to create sin function with 2 decimal places, using only integer numbers.

[richard]

The line:

casts it as floating point. If you haven't used floating point math, you have your research cut out for you.

its a double precision 64 bit float too boot