Updating deprecated torch.trtrs

[mattcleigh]

Issue

The function torch.trtrs is an alias for the now deprecated torch.triangular_solve.
https://pytorch.org/docs/stable/generated/torch.triangular_solve.html

The alias itself has been completely removed in later pytorch releases (>2.1).

normflows calls this unsupported alias which results in an attribute error when running the _LULiner layers with use_cache=True.

normalizing-flows/normflows/flows/mixing.py

Line 508 in 1d9707e

lower_inverse, _ = torch.trtrs(identity, lower, upper=False, unitriangular=True)

Solution

Replace the unsupported alias with the recommended function torch.linalg.solve_triangular (already used elsewhere in the project).
https://pytorch.org/docs/stable/generated/torch.linalg.solve_triangular.html

This requires swapping the order of the inputs while also removing extra (and ignored) returned copies.

[VincentStimper]

Sounds good, thanks!

There is the same problem with the test that also occurred for this PR. We'll try to fix it soon so we can merge these changes.

[mattcleigh]

Thanks a bunch. Let me know if you need anything more from me.