Fix: Floor.mutate(). Geometry drift from repeated calls

[fcarvajalbrown]

Overview

Floor.mutate() was applying transforms by undoing the previous mutation (reverse angle, inverse scale) and then applying the new one.
This approach is not a true inverse — the undo math is order-dependent, and floating-point compound roundings on every call.
The result is that calling mutate() multiple times on the same floor progressively incorrect geometry, a problem for ML data augmentation pipelines that generate multiple crops at different angles.

Changes

MLStructFP/db/__init__.py
MLStructFP/db/_floor.py

• Added _original_points: Optional[Dict] field to Floor, initialized to None in __init__.
• On the first mutate() call, the original (x, y) of every point across all components is snaps hotted (?) into _original_points, assigned by object identity.
• On every further call, points are restored from the snapshot before the transform is applied, so each subsequent mutation is always computed from a clean, exact baseline with no accumulated error.
• Removed the old undo logic (self.mutate(-_angle, 1/_sx, 1/_sy, ...)), which was the source of the bug; after testing.
• No breaking API changes.

Testing

A standalone test file (test_floor_mutate.py) is available in case for addition to the repository, the results are the following:

17 tests, all passing.

test_identity_is_noop (__main__.TestMutateBasic.test_identity_is_noop) ... ok
test_rotate_180 (__main__.TestMutateBasic.test_rotate_180) ... ok
test_rotate_90 (__main__.TestMutateBasic.test_rotate_90) ... ok
test_scale_only (__main__.TestMutateBasic.test_scale_only) ... ok
test_double_call_same_angle_no_drift (__main__.TestMutateIdempotency.test_double_call_same_angle_no_drift) ... ok
test_fifty_calls_no_drift (__main__.TestMutateIdempotency.test_fifty_calls_no_drift) ... ok
test_sequential_different_mutations_resolve_from_origin (__main__.TestMutateIdempotency.test_sequential_different_mutations_resolve_from_origin) ... ok
test_identity_after_mutation_restores_original (__main__.TestMutateRestore.test_identity_after_mutation_restores_original) ... ok      
test_second_scale_applies_to_original_not_first (__main__.TestMutateRestore.test_second_scale_applies_to_original_not_first) ... ok    
test_scale_first_vs_rotate_first_differ_nonuniform (__main__.TestMutateScaleOrder.test_scale_first_vs_rotate_first_differ_nonuniform) ... ok
test_uniform_scale_order_irrelevant (__main__.TestMutateScaleOrder.test_uniform_scale_order_irrelevant) ... ok
test_bb_cache_invalidated (__main__.TestMutateState.test_bb_cache_invalidated) ... ok
test_mutator_properties_after_mutate (__main__.TestMutateState.test_mutator_properties_after_mutate) ... ok
test_mutator_properties_before_mutation (__main__.TestMutateState.test_mutator_properties_before_mutation) ... ok
test_snapshot_created_on_first_call (__main__.TestMutateState.test_snapshot_created_on_first_call) ... ok
test_snapshot_not_overwritten_on_subsequent_calls (__main__.TestMutateState.test_snapshot_not_overwritten_on_subsequent_calls) ... ok  
test_snapshot_values_match_pre_mutation_coordinates (__main__.TestMutateState.test_snapshot_values_match_pre_mutation_coordinates) ... 
ok

----------------------------------------------------------------------
Ran 17 tests in 0.004s

OK

[ppizarror]

Hi. Thanks for pointing this out. Can you,

1. Fix some broken tests
2. It is not necessary to refer, in function docs, to "Unlike the previous implementation".

I think function/class docs should focus on the present, comments on past & present, and TODOs for the future.

[fcarvajalbrown]

Hi. Thanks for pointing this out. Can you,

1. Fix some broken tests

2. It is not necessary to refer, in function docs, to "Unlike the previous implementation".

I think function/class docs should focus on the present, comments on past & present, and TODOs for the future.

Will fix, regardless, since I see that you have experience and on the same location do you mind if I email you with unrelated questions regarding academia and code please? Thank you in advance Pablo.

[ppizarror]

Hi. Thanks for pointing this out. Can you,

1. Fix some broken tests

2. It is not necessary to refer, in function docs, to "Unlike the previous implementation".

I think function/class docs should focus on the present, comments on past & present, and TODOs for the future.

Will fix, regardless, since I see that you have experience and on the same location do you mind if I email you with unrelated questions regarding academia and code please? Thank you in advance Pablo.

Hi @fcarvajalbrown , sure feel free to email me for these reasons.