The question is quite simple; almost every computer language today provides the $\exp(x)$ function in their standard library to compute expressions like $ke^{-(x - h)^2}.$ However, I would like to know whether this function is the fastest way to compute the above expression. In other words, is there some way to compute $ke^{-(x - h)^2}$ faster than $\exp(x)$ in standard libraries while keeping the result very accurate?

I would like to specify that Taylor series will not work for my application, nor will any other polynomial approximations.

In the end, I wish to compute a series of these expressions, $$\sum^n_{i = 0} k_ie^{-(x - h_i)^2}$$ for some integral $n \geq 0.$