Welcome to GWSurrogate!

GWSurrogate is an easy to use interface to gravitational wave surrogate models.

Surrogates provide a fast and accurate evaluation mechanism for gravitational waveforms which would otherwise be found through solving differential equations. These equations must be solved in the ``building" phase, which was performed using other codes. For details see

[1] Scott Field, Chad Galley, Jan Hesthaven, Jason Kaye, and Manuel Tiglio. `"Fast prediction and evaluation of gravitational waveforms using surrogate models". Phys. Rev. X 4, 031006 (2014). arXiv: gr-qc:1308.3565

If you find this package useful in your work, please cite reference [1] and, if available, the relevant paper describing the specific surrogate used.

All available models can be found in gwsurrogate.catalog.list()

gwsurrogate is available at https://pypi-hypernode.com

Installation

Dependency

gwsurrogate requires:

1. gwtools. If you are installing gwsurrogate with pip you will automatically get gwtools. If you are installing gwsurrogate from source, please see https://bitbucket.org/chadgalley/gwtools/

2. gsl. For speed, the long (hybrid) surrogates use gsl's spline function. To build gwsurrogate you must have gsl installed. Fortunately, this is a common library and can be easily installed with a package manager.

Note that at runtime (ie when you do import gwsurrogate) you may need to let gsl know where your BLAS library is installed. This can be done by setting your LD_PRELOAD or LD_LIBRARY_PATH environment variables. A relevant example:

>>> export LD_PRELOAD=~/anaconda3/envs/python27/lib/libgslcblas.so

From pip

The python package pip supports installing from PyPI (the Python Package Index). gwsurrogate can be installed to the standard location (e.g. /usr/local/lib/pythonX.X/dist-packages) with

>>> pip install gwsurrogate

From conda

gwsurrogate is on conda-forge, and can be installed with

>>> conda install -c conda-forge gwsurrogate

From source

First, please make sure you have the necessary dependencies installed (see above). Next, Download and unpack gwsurrogate-X.X.tar.gz to any folder gws_folder of your choosing. The gwsurrogate module can be used immediately by adding

import sys
sys.path.append('absolute_path_to_gws_folder')

at the beginning of any script/notebook which uses gwsurrogate.

Alternatively, if you are a bash or sh user, edit your .profile (or .bash_profile) file and add the line

export PYTHONPATH=~absolute_path_to_gws_folder:$PYTHONPATH

For a "proper" installation

>>> python setup.py install    # option 1
>>> pip install -e gwsurrogate # option 2

where the "-e" installs an editable (development) project with pip. This allows your local code edits to be automatically seen by the system-wide installation.

If you have git cloned this project, you must do

git submodule init
git submodule update

Usage

Available models

To get a list of all available surrogate models, do:

>>> import gwsurrogate
>>> gwsurrogate.catalog.list()
>>> gwsurrogate.catalog.list(verbose=True)      # Use this for more details

Current models

The most up-to-date models are listed below.

• NRSur7dq4: For generically precessing BBHs, trained on mass ratios q≤4. Paper: arxiv:1905.09300.
• NRHybSur3dq8: For nonprecessing BBHs, trained on mass ratios q≤8. Paper: arxiv:1812.07865.

Download surrogate data and load it

Pick a model, let's say NRSur7dq4 and download the data. Note this only needs to be done once.

gwsurrogate.catalog.pull('NRSur7dq4')       # This can take a few minutes

Load the surrogate, this only needs to be done once at the start of a script

sur = gwsurrogate.LoadSurrogate('NRSur7dq4')

Evaluate the surrogate

q = 4           # mass ratio, mA/mB >= 1.
chiA = [-0.2, 0.4, 0.1]         # Dimensionless spin of heavier BH
chiB = [-0.5, 0.2, -0.4]        # Dimensionless of lighter BH
dt = 0.1                        # timestep size, Units of total mass M
f_low = 0                # initial frequency, f_low=0 returns the full surrogate

# h is dictionary of spin-weighted spherical harmonic modes
# t is the corresponding time array in units of M
# dyn stands for dynamics, do dyn.keys() to see contents
t, h, dyn = sur(q, chiA, chiB, dt=dt, f_low=f_low)

There are many more options, such as using MKS units, returning the polarizations instead of the modes, etc. Read the documentation for more details.

help(sur)

Jupyter notebooks located in tutorial/website give a more comprehensive overview of individual models.

Tests

If you have downloaded the entire project as a tar.gz file, its a good idea to run some regression tests. Note that if you are running the model regression tests, regression data must be generated locally on your machine.

>>> cd test                          # move into the folder test
>>> python test_model_regression.py  # create model regression data
>>> cd ..                            # move back to the top-level folder
>>> pytest                           # run all tests
>>> pytest -v -s                     # run all tests with high verbosity

NSF Support

This package is based upon work supported by the National Science Foundation under PHY-1316424, PHY-1208861, and PHY-1806665.

Any opinions, findings, and conclusions or recommendations expressed in gwsurrogate are those of the authors and do not necessarily reflect the views of the National Science Foundation.