Please feel free to contact me if you are having any problems: lloydripley[at]gmail[dot]com
I have only tested everything on *nix machines, using the GNU C++ compiler (version 4.8.5 onwards, C++11 standard).
FFTW is an open source library that computes fast Fourier transforms. It can be found at http://www.fftw.org/
I assume that you have have FFTW3 installed.
If not, and if you are using a home computer, then you should be able
to install FFTW using a package manager.
If you are on a computer cluster, then it should be available
using module load [...]
shtns is an open source library that can perform scalar and vector spherical harmonic transforms. It is very fast, and has been extensively used and tested in the context of geophysical fluid simulations.
shtns can be found at https://nschaeff.bitbucket.io/shtns/
I assume that when you install shtns, that you will make
a new directory within shtns called Library, and
install shtns using use
./configure --prefix=$(HOME)/shtns/Library
googletest is an open source unit test framework for C++.
googletest cane be found at https://github.com/google/googletest
The internal googletest README.md file should contain all the necessary installation instructions.
The following stackoverflow Q&A may be useful as well.
https://stackoverflow.com/questions/13513905/how-to-set-up-googletest-as-a-shared-library-on-linux
There are two options for the executable: with either
Chebyshev psuedopsectral methods for computing the radial
derivatives, or a finite difference emthod.
There are flags for this in Source/Makefile.
Then in the main directory, typing Make should compile the executable
to Bin.