FEAT: add option to crop whitened time series by ColmTalbot · Pull Request #1030 · bilby-dev/bilby

ColmTalbot · 2025-12-23T17:04:34Z

This PR implements the proposed modification to the likelihood from https://iopscience.iop.org/article/10.1088/1361-6382/ae1ac7/meta.

The main new feature is adding a crop_duration to the InterferometerStrainData and some accompanying utility code.

I modified how the GravitationalWaveTransient and BasicGravitationalWaveTransient call the data. I did not have to change the reference likelihood tests, so there is good evidence that this doesn't impact the numerical values when not using the cropping.

I suspect there is a performance penalty due to repeatedly whitening the data. There should be a way to cache this calculation, it just requires some cleverness about when the time/frequency masks might have changed.

I'm not sure at this time how this should interact with accelerated likelihood, so I've left them alone.
~~I also haven't validated how this interacts with time/calibration marginalization.~~

mj-will · 2026-01-22T15:46:28Z

test/gw/detector/interferometer_test.py

+    @property
+    def frequency_mask(self):
+        frequencies = bilby.core.utils.series.create_frequency_series(
+            duration=self.ifo.cropped_duration, sampling_frequency=self.sampling_frequency
+        )
+        return (self.ifo.minimum_frequency <= frequencies) & (
+            frequencies <= self.ifo.maximum_frequency
+        )
+


We should probably have a utility function that does this.

GregoryAshton

Overall looks good and I'm supportive, just a few things I wanted to check.

bilby/gw/detector/interferometer.py

bilby/gw/likelihood/base.py

bilby/gw/detector/interferometer.py

asb5468 · 2026-02-05T15:50:32Z

bilby/gw/detector/interferometer.py

+        else:
+            return self.whiten_and_crop(frequency_series=frequency_series)
+
+    def whiten_and_crop(self, frequency_series : np.array) -> np.array:


It seems like this procedure is more fundamental than suggested by its being a method of the interferometer class. The nice thing about using the gwutils SNR functions was that you could calculate SNRs using them without necessarily initializing an interferometer object. Is it possible to pull this out to the utils and just call it here?

GregoryAshton · 2026-02-09T10:05:53Z

bilby/gw/utils.py

+    return np.nan_to_num(whitened) * frequency_mask * (4 / duration)**0.5
+
+
+def whiten_and_crop(frequency_series, amplitude_spectral_density, frequency_mask, time_mask, duration):


Should the name state what input it accepts? E.g. like 'frequency_domain_whiten' to make it clear it is acting on the frequency-domain input?

I can make this change, but it's pretty clear from the signature and docstring.

GregoryAshton

A few more comments after another look.

GregoryAshton · 2026-02-09T10:07:59Z

bilby/gw/detector/interferometer.py

-            * np.sqrt(np.sum(self.frequency_mask)) / frequency_window_factor
+            * np.sqrt(np.sum(self.frequency_mask))
+            / frequency_window_factor
+            * self.time_mask.mean()**0.5


Why does this use both np.sqrt and **0.5. It would probably be easier to read if it was consistent.

I think I was trying to avoid explicitly using numpy, but that's unavoidable since we need an fft and sqrt is sometimes meaningfully faster.

Suggested change

* self.time_mask.mean()**0.5

* np.sqrt(self.time_mask.mean())

GregoryAshton · 2026-02-09T10:09:58Z

bilby/gw/detector/interferometer.py

            The frequency series, whitened by the ASD
        """
-        return frequency_series / (self.amplitude_spectral_density_array * np.sqrt(self.duration / 4))
+        if self.crop_duration == 0:


What happens (or can) crop_duration be "None" or None etc? This would silently fail and then trigger the else clause, likely also erroring, but could be confusing?

This would fail in the crop_duration.setter in the InterferometerStrainData with a reasonably explicit error message.

GregoryAshton · 2026-02-09T10:11:56Z

bilby/gw/likelihood/base.py

        )
-        _mask = interferometer.frequency_mask

        if 'recalib_index' in parameters:


Why does the signal no longer require masking here?

Unclear, is this tested?

Co-authored-by: Colm Talbot <talbotcolm@gmail.com>

ColmTalbot added enhancement New feature or request >100 lines detector likelihood to discuss To be discussed on an upcoming call labels Jan 20, 2026

ColmTalbot force-pushed the truncated-likelihood branch from f39871f to 5fbc454 Compare January 21, 2026 15:17

ColmTalbot requested review from a team, GregoryAshton, adivijaykumar, asb5468 and mj-will January 21, 2026 17:52

mj-will reviewed Jan 22, 2026

View reviewed changes

ColmTalbot force-pushed the truncated-likelihood branch from 0b74e2b to 0972d62 Compare January 23, 2026 16:53

ColmTalbot requested a review from mj-will January 26, 2026 08:32

GregoryAshton reviewed Jan 28, 2026

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ColmTalbot commented Jan 28, 2026

View reviewed changes

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ColmTalbot added this to the 3.0.0 milestone Jan 29, 2026

ColmTalbot force-pushed the truncated-likelihood branch 2 times, most recently from b8f4b97 to c7e762a Compare February 5, 2026 14:38

asb5468 reviewed Feb 5, 2026

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GregoryAshton reviewed Feb 9, 2026

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ColmTalbot added 8 commits February 18, 2026 15:45

FEAT: add option to crop whitened time series

5014f4d

FMT: fix precommits

c8453d0

Expose whiten and crop method

d102673

BUG: squash some bugs

e6c6e3c

TST: remove now obsolete test

45fc893

FEAT: add whitened frequeny mask

0e18517

TYPO: fix imports

bd9e29e

BUG: fix imports

7d6a399

GregoryAshton and others added 7 commits February 18, 2026 15:45

Update bilby/gw/detector/interferometer.py

06adb1e

Co-authored-by: Colm Talbot <talbotcolm@gmail.com>

DOC: fix docstring

1e7086e

REFACTOR: move whitening functions into gwutils

730a12e

BUG: pre-commit fixes

032763b

BUG: typo fix

f3bec33

TYPO: remove old argument

a52830d

TYPO: typo fixes in whitening function

85294b4

ColmTalbot force-pushed the truncated-likelihood branch from 962bc37 to 85294b4 Compare February 18, 2026 20:45

		return np.nan_to_num(whitened) * frequency_mask * (4 / duration)**0.5


		def whiten_and_crop(frequency_series, amplitude_spectral_density, frequency_mask, time_mask, duration):

	* self.time_mask.mean()**0.5
	* np.sqrt(self.time_mask.mean())

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ColmTalbot commented Dec 23, 2025 •

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