Installation

To get started with synthesizer you need to complete the following setup steps.

• Create a python environment

• Clone the code base

• Install the code

• Download a stellar population synthesis (SPS) grid

Creating a python environment

First create a virtual python environment (synthesizer has been tested with Python 3.10). You should replace this path with where you wish to install your virtual environment:

python3 -m venv /path_to_new_virtual_environment
source /path_to_new_virtual_environment/bin/activate

Cloning and installing the code

You can then clone the latest version of synthesizer from github, and finally install it:

git clone https://github.com/flaresimulations/synthesizer.git
cd synthesizer
pip install .

If you want to install the code in editable mode, so any changes in the code base will be reflected in the installation:

pip install .

Make sure you stay up to date with the latest versions through git:

cd synthesizer
git pull origin main

Installing with optional flags

DISCLAIMER: most users do not need to worry about this section. Synthesizer, by design, simplifies compilation so the user doesn’t need to think about it.

Synthesizer uses C extensions for much of the heavy lifting done in the background to derive spectra. By default Synthesizer will use -std=c99 -Wall -O3 -ffast-math -g (on a unix-system) to optimise agressively. You can override this by modifying the compiler flags and linker arguments at the point of install, e.g.

` CFLAGS=... LDFLAGS=... pip install . `

Setting these environment variables will override the default flags. Note that Synthesizer will santise any requested flags to ensure they are compatible with the compiler. For example, to compile with debugging symbols and no optimisation, you could use

` CFLAGS="-std=c99 -Wall -g" LDFLAGS="-g" pip install . `

which would be recommended if you are developing the code, particularly the C extensions. In addition to disabling optimisation and turning on debugging symbols, you can also turn on debugging checks by adding WITH_DEBUGGING_CHECKS=1, e.g.

` CFLAGS="-std=c99 -Wall -g" WITH_DEBUGGING_CHECKS=1 pip install . `

This will add additional checks to the code to help catch bugs, but will slow down the code. This is recommended if you are developing the code, but not for normal use.

The build process will generate a log file (build_synth.log) which details the compilation process and any choices that were made about the requested flags. If you encounter any issues, please check this log file for more information.

Downloading SPS grids

Once you’ve installed the code, you’re almost ready to get started with Synthesizer. The last step is to download an SPS grid file, described in the next section.