Running COMPAS using a grid file¶

In population synthesis, the initial stellar population is usually generated by drawing the primary mass, secondary mass, semi-major axis, and eccentricity from their respective distributions specified in the program options. However, we illustrate COMPAS's ability to specify a grid of initial values for single and binary star evolution using COMPAS's grid functionality.

An example grid file, Grid_demo.txt, is included in the detailed_evolution directory. Open it with a text editor to view it:

# Demo BSE Grid file

--initial-mass-1 35.4 --initial-mass-2 29.3 --metallicity 0.001  --eccentricity 0.000000e+00 --semi-major-axis 1.02

It should be clear that this grid file specifies a binary of zero-age main sequence stars with primary mass 35.4$\small M_\odot$, secondary mass 29.3$\small M_\odot$, metallicity 0.001, zero eccentricity, and semi-major axis of 1.02AU. See Grid files for detailed information regarding COMPAS's grid functionality for both single and binary stars.

We will execute COMPAS via the runSubmit.py script, but first we need to edit the companion compasConfigDefault.yaml script to instruct COMPAS to read the grid file (via the grid program option).

Open $COMPAS_ROOT_DIR/preProcessing/compasConfigDefault.yaml with a text editor, and specify the grid filename:

grid_filename = 'Grid_demo.txt'

Note the quotes around the filename.

If the filename specified is not fully-qualified, and the shell environment variable COMPAS_INPUT_DIR_PATH exists and is not empty, the value of COMPAS_INPUT_DIR_PATH will be prepended to the specified grid filename.

To print the detailed evolution of binary properties over time, we need to turn on detailed output, by specifying:

detailed_output = True

in compasConfigDefault.yaml.

COMPAS can produce logfiles of different types: HDF5, CSV, TSV, and TXT, which can be chosen by editing the line:

logfile_type = 'HDF5'

in compasConfigDefault.yaml. The default type is HDF5 - we'll leave the default.

NOTE: we are currently updating our documentation and will include a compasConfigDefault.yaml for the demo asap.