gw-mbank 0.3.1

Metric bank generation for gravitational waves data analysis

mbank

mbank is a code for fast Gravitational Waves template bank generation. It creates a bank of binary black hole (BBH) systems. It is very handy for generating precessing and eccentric banks.

If you want more details, you can take a look at the documentation. Otherwise, you can keep reading and learn the essentials below.

How it works

In order to search for a Binary Black Hole (BBH) signal, one needs to come up with a set of templates (a.k.a. bank), signals that will be searched in the noisy data from the interferometers. Generating a bank is a tedious work, requiring to place huge number of templates so that their mutual distance is as constant as possible. Unfortunately the computation of such distance is highly expensive and, if we want to expand the parameter space covered by the searches, we are very interested to get a reliable bank covering an high dimensional space at a decent cost.

This is exactly the purpose of mbank: thanks to a cheap approximation to the distance between templates, it provides a very fast bank generation method, which can be successfully employed for high dimensional bank generation. The approximation consist in replacing the complicated distance with a metric distance (i.e. a bilinear form).

The bank generation algorithm works in 4+1 steps:

1. Defining a metric approximation
2. Computing the metric on a small set of points all around the space (a.k.a. tiling the space)
3. Optional: training a normalizing flow to interpolate the metric
4. Placing the templates according to the tiling
5. Validate the bank by means of injections

mbank is the code that does all of this for you!

How to install

To install the latest released verion (no release has been done yet):

pip install gw-mbank

To intall the latest version in the github repository, you can type:

pip install git+https://github.com/stefanoschmidt1995/mbank

Otherwise, you can clone the repo, build a distribution and install the package:

git clone [e-mail]:stefanoschmidt1995/mbank.git
cd mbank
python setup.py sdist
pip install dist/mbank*.tar.gz

This will install the source code as well as some executables that makes the bank generation easier (plus the dependencies).

How to use

To generate a bank you can use the executable mbank_run. Make sure you have a PSD file (either in csv file either in ligo xml format). You will need to choose:

• The BBH variables that you want to vary within the bank (--variable_format parameter)
• The minimum match (--mm), that controls the average spacing between templates
• The range of physical parameters you want to include in the bank (note that the spins are always expressed in spherical coordinates)
• Low and high frequency for the match/metric computation (--f-min and --f-max)
• The WF FD approximant (it must be lal)
• Maximum number of templates in each tile: this tunes the hierarchical tiling (--template-in-tile argument)
• A coarse grid for tiling: the tiling can be parallelized and performed independently on each split (--grid-size argument)
• The placing method --placing-method for the templates in each tile ('geometric', 'stochastic', 'pure_stochastic', 'uniform', 'iterative', 'random'). The 'stochastic' method is recommended.

If you don't have a favourite PSD, you can download one with wget https://dcc.ligo.org/public/0165/T2000012/002/aligo_O3actual_H1.txt.

An example command to generate a simple non-precessing bank is:

mbank_run \
	--run-name myFirstBank \
	--variable-format Mq_s1z_s2z \
	--grid-size 1,1,2,2 \
	--mm 0.97 \
	--tile-tolerance 0.5 \
	--max-depth 10 \
	--psd ./aligo_O3actual_H1.txt --asd \
	--f-min 15 --f-max 1024 \
	--mtot-range 20 75 \
	--q-range 1 5 \
	--s1-range 0.0 0.99 \
	--s2-range -0.99 0.99 \
	--plot \
	--placing-method stochastic \
	--empty-iterations 100 \
	--approximant IMRPhenomPv2 \
	--use-ray 

To know more information about the available options type:

mbank_run --help

This is how the output bank look like:

You can also use the metric to estimate the fitting factor for a bunch of injections:

mbank_injections \
	--n-injs 10000 \
	--variable-format Mq_s1z_s2z \
	--tiling-file out_myFirstBank/tiling_myFirstBank.npy \
	--bank-file out_myFirstBank/bank_myFirstBank.xml.gz \
	--psd ./aligo_O3actual_H1.txt --asd \
	--approximant IMRPhenomPv2 \
	--f-min 15 --f-max 1024 \
	--plot

If you specify the --full-match option, the match will be recomputed without a metric approximation: in this case, you want to speed things up with something like --use-ray and --cache (if you have enough memory). You can also throw some injection chosen from a file: you just need to set an input xml injection file with the --inj-file option.

Here's the injection recovery:

If you don't feel like typing all the options every time, you can add them to a text file myFirstBank.ini and pass it to the command: it will figure out by itself. You can find some example ini files in the repo. To run them:

mbank_run my_first_eccentric_bank.ini
mbank_injections my_first_eccentric_bank.ini

As you see, the same file can be used for different commands: each command will just ignore any option not relevant for it.

Contacts

Fore more info, or just to say hello, you can contact me: [e-mail].