Detailed compilation instructions for Linux, Mac, and Windows.

Dependencies / Requirements

C++ compiler that supports C++17
- Tested with clang version 6 and newer; gcc version 7 and newer
- Tested with g++ and clang++ on linux and mac
- Also tested with Intel [icc 2021.9.0], though this is tested infrequently
LAPACK and BLAS libraries netlib.org/lapack/
GSL (GNU scientific libraries) gnu.org/software/gsl/ [version 2.0 or newer*]
- (it should also work with older versions of GSL, but this is not regularly tested and therefore not guaranteed)
- Updated to work with newer GSL version 2.8; still works with older versions too
[optional] GNU Make (gnu.org/software/make/) - used to compile code
[optional] OpenMP (openmp.org/) - used for parallelisation
[optional] git (git-scm.com/) for version tracking and to keep up-to-date with latest version
The shell script install-dependencies.sh will attempt to automatically install the required dependencies

Compilation: Linux

Instructions for ubuntu; similar commands for other flavours
Install make: sudo apt-get install make
Install GSL libraries: sudo apt-get install libgsl-dev
May also need LAPACK/BLAS libraries: sudo apt-get install libatlas-base-dev liblapack-dev libblas-dev
Install the compiler: sudo apt-get install g++ and/or sudo apt-get install clang++
Then compile by running make from the ampsci directory
To use with openMP (for parallelisation) with clang++, you might have to also install clang openmp libraries: sudo apt install libomp-dev
- You'll often need the exact versions to match. So, if using clang++-15, install libomp-dev-15.

On mac: use homebrew to install gsl: brew install gsl
homebrew is a package manager; install from https://brew.sh/
Seems to work best with the homebrew version of gcc. Install as: brew install gcc
Note: you may need to change the compiler from g++ to g++-9 (or similar), or update your environment variables, since calling g++ on mac actually calls clang++ by default
You might have to tell the compiler how to link to the GSL library; in Makefile:
- GSL_PATH=/usr/local/opt/gnu-scientific-library
Then compile by running make from the ampsci directory
Use openMP for parellelisation when using clang++ on mac:
- If using g++, should work as per normal
- To use openMP with clang, seem to require the llvm version
- brew install llvm
- Then, in the Makefile, set (exact paths may be different for you):
  - CXX = /usr/local/opt/llvm/bin/clang++
  - CARGS += -I/usr/local/opt/llvm/include/
  - LARGS += -l/usr/local/opt/llvm/lib/
- This seems fragile

Mostly the same as above, but some of the libraries are installed to different directories by default. In particular:
GSL_PATH=/opt/homebrew/Cellar/gsl/2.7

For windows, the easiest way (for me, anyway) is to use the 'windows subsystem for linux' (requires Windows 10+).
Instructions on installation/use here: docs.microsoft.com/en-us/windows/wsl/install.
Then, the compilation + use can proceed as per Linux above.
You may have some luck getting the MSVC compiler working, but linking to libraries will be difficult

Various basic options can be specified in the Makefile:

## Which compiler: (g++, clang++)

CXX = g++

Build modes:
- Choose one of release/dev/debug
- release (default) – turns off warnings and checks. This is fine for main branch if you haven't modified anything, but should not be used if you are modiying the code
- dev – please use dev mode, which turns on checks and warning, if you are modyfying the code. This will help to catch any errors or issues
- debug – will be slow, but turns on some debugging options to make debugging easier

## Build mode (changes warnings + optimisation level): release/dev/debug

MODE ?= release

Path to the GSL libraries. This can be left blank the majority of the time. On some systems if GSL is not found natively, or if the incorrect labrary is being found, you might need to specify it
- e.g., on newer M1/M2 macs, you may need /opt/homebrew/Cellar/gsl/2.7.1/
- intel mac: /usr/local/opt/gnu-scientific-library
- the configure.sh script should have done this for you

## Path to the GSL library. Usually, this can be left blank. 
## Exact path will depend on where GSL has been installed. 
GSL_PATH ?=

Libraries. Again, usually the default is fine.
- On some systems, different libraries are used (e.g., openblas vs. blas)
- In particular, on Firday cluster: -lgsl -lgslcblas -lopenblas
- On Bunya: -lgsl -lgslcblas -llapack -lopenblas -lgfortran

## Set GSL and LAPACK/BLAS library flags. These are typical, but sometimes differ

LDLIBS ?= -lgsl -lgslcblas -llapack -lblas

## OpenMP library to use. Comment out or leave blank for no OpenMP

OMPLIB ?= -fopenmp

Extra compiler/linker arguments: usually blank, but you may add to these, which are passed as compiler and linker arguments

# Use these to pass in any other compiler/linker arguments (Rarely needed)
CARGS ?=
LARGS ?=