📦 WP-091c — refine(decode): rotated geometry in the geometry module¶
Research log · Phase 9 — Inference and generalization
WP-091c — what a refactor is allowed to notice¶
The move itself is unremarkable: rotated_iou and the seven private helpers it exclusively owns leave eval/dota_eval.py for data/rotated_geom.py, since an evaluation module had no business being on the decode path's import graph for a function that is pure geometry. What the package is worth recording for is the three things it declined to do.
It did not merge the duplicate it found. rotated_geom already had _check_2d, differing from the arriving _check_rboxes only in the letter naming the row count — and the two raise must be (N, 5) and must be (K, 5), which two different test files match on. Merging them is therefore a test-visible behaviour change wearing the costume of a duplicate removal, and a refactor whose contract is "every existing test passes unchanged" cannot also change what an error says. It is recorded as 091d instead. A duplicate that is cheap to see is not always cheap to remove, and the difference is whether anything asserts on it.
The search also turned up _check_rboxes in losses/probiou.py, first reported as a third copy and corrected on re-reading: it guards ndim == 0 or shape[-1] != 5 and raises must be (..., 5), so it accepts arbitrary leading dimensions where both rotated_geom validators require exactly 2-D. Same name, same five, different contract — merging it into the other two would tighten what the loss path accepts, which is a behaviour change and not a rename. It is 091e, and its test coverage differs in the same direction: tests/losses/test_probiou.py matches the prefix target must be only, leaving the tail unpinned, where both rotated_geom messages are pinned tail and all. Three lookalikes, two of them the same check — the way to tell was to read each guard rather than each name.
It did not deprecate the old name. pyDeprecate is nowhere in this tree, and warnings.warn would have fired on both existing suites — which is not "tests pass unchanged" under any honest reading, and arms a trap for the day filterwarnings = error is set. The deeper reason is that dota_eval.rotated_iou is not a legacy alias: that module's docstring defines R18's protocol in terms of its overlap measure, so a caller reproducing the protocol wants the kernel where the protocol is. One function visible from two places is what canonicalize already is.
It moved the argument, not just the code. The "why there is no float64 here" section and its five-row error table went with the kernel, because that table is the evidence for the shift-before-expand ordering rather than commentary about it; a precision argument left behind in the module that no longer owns the arithmetic is how a constraint quietly stops being checked. Two claims in the destination's own docstring also had to change or become false — "no Python loop over boxes" and a blanket "float32 tensors" — which is the ordinary tax of moving code into prose written before it arrived.
The evidence that the move was inert is the goldens and only the goldens. rotated_iou sits on the scoring path, and a silently perturbed kernel would still clear the shapely oracle's 1e-4 tolerance; 20/20 unmoved, frozen subtrees included, is what says the arithmetic is bit-identical.
WP-091b had already verified there was no import cycle, from four entry orders, and left the module where it was rather than widening its own diff — which is why this is a package and not a line in that one.