fmath.hpp (https://github.com/herumi/fmath, fast approximate float function fmath)
| CPU | OS | compiler | std::exp | fmath::expd | one element for fmath::expd_v(array version) |
|---|---|---|---|---|---|
| Xeon X5650 2.67GHz | 64-bit Linux | gcc 4.6.0 | 128.89 | 27.38 | 17.84 |
| i7-2600 3.4GHz | 64-bit Linux | gcc 4.4.5 | 69.11 | 12.10 | 8.25 |
| i7-2600 3.4GHz | 64-bit Windows 7 | VC10 | 36.33 | 14.37 | 7.08 |
The function double fmath::expd(double) defined in fmath.hpp is about five time faster than std::exp of gcc-4.6 on 64-bit Linux and about two point five faster than that of Visual Studio 2010 on 64-bit Windows.
The error of rms (Root Mean Square) for 1000000 points generated from standard normal distribution is about 1.117645e-16.
The source code for benchmark is fastexp.cpp, which requires Xbyak.
I write some results for various environments in the comment of the header of fastexp.cpp.
Moreover, fmath.hpp provies fmath::exp(float) and fmath::log(float).
These functions are also 2~5 times faster than those of standard library.
Let's try it if you want speed.
