This is a Modern Fortran library for fast, approximate math functions: exp, log, 1/sqrt.
These functions provide fast, approximate evaluations of the exponential, logarithm and normalization functions in 64-bit precision.
A detailed explanation of the underlying math with the IEEE-754 representation is reported in ref [1].
For each function, a module is provided; the interface has both simple functions and a programmable object-oriented wrapper.
This code is released under MIT license; please cite the following reference whenever using it.
[1] F. Perini, R.D. Reitz, "Fast approximations of exponential and logarithm functions combined with efficient storage/retrieval for combustion kinetics calculations" Combustion and Flame 194(2018), 37-51.
An automated build is not available yet.
src/fast_exp.f90contains the exponential routinessrc/fast_log.f90contains the logarithm routinessrc/fast_rsqrt.f90contains the 1/sqrt(x) routines.test/test.f90is the test driver program
Each module has no external dependencies, they can also be used individually.
A simple command line build script is:
gfortran src/fast_exp.f90 src/fast_log.f90 src/fast_rsqrt.f90 test/test.f90 -o fastmath_test.exe
A simple makefile for the GNU compiler suite is provided in folder project; to run it:
cd project/
make -f makefile.gcc
The testing executable compares performance and accuracy wrt the compiler's intrinsics functions.