fix: remove unconditional inplace_mask_diag that overrides owner self…

[greatjourney589]

Description

Remove a stray unconditional inplace_mask_diag(&mut weights) call in epoch_dense_mechanism that immediately followed the owner self-weight exception block. When an owner_uid is present, the if branch correctly calls inplace_mask_diag_except_index to preserve the owner's self-weight on the diagonal. However, the redundant call afterward would unconditionally zero the entire diagonal — silently overriding and negating that exception on every epoch.

Related Issue(s)

• Closes #[issue number]

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

N/A — this fix restores intended behavior and does not alter any public interfaces.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

Please include any relevant screenshots or GIFs that demonstrate the changes made.

Additional Notes

The removed line appears to be a leftover from before the owner self-weight exception was introduced. The if let Some(owner_uid) block already handles both branches (inplace_mask_diag_except_index for the owner case, inplace_mask_diag for the general case), making the unconditional call after the block both redundant and harmful.

[greatjourney589]

Hi @open-junius @sam0x17 @gztensor @JohnReedV @camfairchild
I discovered a potential issue during codebase exploration. I’d appreciate your review of this PR.

[camfairchild]

utACK

Thanks for the contribution

[camfairchild]

Please write a test for this also

[greatjourney589]

Please write a test for this also

A corresponding test has been added. Thank you for catching that.