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NIFTy-PPL / NIFTy

Probabilistic programming framework for signal inference algorithms that operate regardless of the underlying grids and their resolutions
https://ift.pages.mpcdf.de/nifty/index.html
GNU General Public License v3.0
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Hartley transform implementation in re.correlated_field #9

Open StandingWaves opened 3 months ago

StandingWaves commented 3 months ago

In nifty8.re.correlated_field the Hartley transform is defined as the sum of the real and the imaginary part of the Fourier transform. According to various other sources, e.g. [1], I think it should be their difference.

[1] Analytic Properties of the Hartley Transform and their Implications

Edenhofer commented 3 months ago

Thanks for filing this issue! This has been a long standing pain point in NIFTy. The only reason why we haven't switched by now is because this would break reading in any previous reconstruction. See this issue.

I propose that we'll add a config option so that users can use the proper Hartley transform while keeping the current default for now for legacy reasons. @mreineck What do you think?

Edenhofer commented 3 months ago

I leave this issue open as we might want to switch the default with a new major release.