Approximate e^x

Question

I\'d like to approximate the e^x function.

Is it possible to do so using multiple splines type based approach? i.e between x₁

Answer 1

This is not appropriate for custom FPGA, but worth mentioning.

http://www.machinedlearnings.com/2011/06/fast-approximate-logarithm-exponential.html

And the source code:

https://code.google.com/archive/p/fastapprox/downloads

The "faster" implementation only involves 3 steps (multiply, add, convert float to int) and a final cast back to float. In my experience, it is 2% accurate, which may be enough if you don't care about the actual value but are using the value in a log-likelihood maximization iteration.