Fft cleanup/update

[aymuos15]

Remove legacy PyTorch 1.8.0 compatibility code from FFT utilities. MONAI now requires PyTorch ≥ 2.4.1, so the version checks and NumPy fallbacks are no longer needed.

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).

[coderabbitai]

📝 Walkthrough

Walkthrough

Removes embedded version check logic and related documentation from FFT utility functions. In fft_utils_t.py, removes docstring notes from four functions. In transforms/utils.py, eliminates runtime PyTorch version branching in Fourier.shift_fourier and Fourier.inv_shift_fourier, consolidating to direct use of torch.fft functions. Numeric computation paths unchanged for both Tensor and NumPy inputs.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Title check	❓ Inconclusive	Title refers to the main change (FFT cleanup) but is somewhat vague and generic.	Consider a more specific title like 'Remove legacy PyTorch 1.8.0 compatibility from FFT utilities' to clarify what cleanup entails.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description check	✅ Passed	Description includes the rationale and change type, but lacks detail on what specific version checks and fallback paths were removed.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

monai/transforms/utils.py (1)

1886-1908: ⚠️ Potential issue | 🟡 Minor

Remove unused parameter n_dims.

The n_dims parameter is not referenced in the function body and is not documented in the Args section. Callers pass values to the spatial_dims parameter (second positional argument), leaving n_dims unused throughout.

Proposed fix

     `@staticmethod`
     def inv_shift_fourier(
-        k: NdarrayOrTensor, spatial_dims: int, n_dims: int | None = None, as_contiguous: bool = False
+        k: NdarrayOrTensor, spatial_dims: int, as_contiguous: bool = False
     ) -> NdarrayOrTensor:

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@monai/transforms/utils.py` around lines 1886 - 1908, The function
inv_shift_fourier has an unused parameter n_dims; remove n_dims from the
function signature and any internal references, update the docstring Args to
drop the n_dims entry, and adjust any call sites that currently pass a third
argument to pass only spatial_dims (or use keyword as_contiguous) so callers
match the new signature; keep the logic using spatial_dims and as_contiguous
unchanged.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Outside diff comments:
In `@monai/transforms/utils.py`:
- Around line 1886-1908: The function inv_shift_fourier has an unused parameter
n_dims; remove n_dims from the function signature and any internal references,
update the docstring Args to drop the n_dims entry, and adjust any call sites
that currently pass a third argument to pass only spatial_dims (or use keyword
as_contiguous) so callers match the new signature; keep the logic using
spatial_dims and as_contiguous unchanged.

---

ℹ️ Review info

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Cache: Disabled due to data retention organization setting

Knowledge base: Disabled due to Reviews -> Disable Knowledge Base setting

📥 Commits

Reviewing files that changed from the base of the PR and between 894068a and 1a1156c.

📒 Files selected for processing (2)

• monai/networks/blocks/fft_utils_t.py
• monai/transforms/utils.py

💤 Files with no reviewable changes (1)

• monai/networks/blocks/fft_utils_t.py

[aymuos15]

I guess the coderabbit comment is preexisting and not in the scope of this PR? I can make that change separately after the decision on this change?

[ericspod]

Thanks for the cleanup!

[ericspod]

I guess the coderabbit comment is preexisting and not in the scope of this PR? I can make that change separately after the decision on this change?

It appears so, yes. It should be removed with a deprecation warning which can be done as a separate PR, though it seems to be low priority.

[aymuos15]

I guess the coderabbit comment is preexisting and not in the scope of this PR? I can make that change separately after the decision on this change?

It appears so, yes. It should be removed with a deprecation warning which can be done as a separate PR, though it seems to be low priority.

Sounds good. Thank you very much. Ill make one then after this is merged. I haven't looked into it to really verify what all that bit of code is touching.