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7 changes: 6 additions & 1 deletion src/dlens/tools/_training.py
Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,13 @@ def train(
self, dataset: DatasetRef, architecture: ArchitectureSpec, config: TrainingConfig
) -> TrainResult:
x, y = load_dataset(dataset)
xn, mu, sd = _standardize(x)
k = dataset.num_classes
counts = np.bincount(y, minlength=k)
missing = [name for name, count in zip(dataset.class_names, counts) if count == 0]
if missing:
# An empty class would get a NaN centroid, which silently wins every argmin.
raise RuntimeError(f"No samples found under {dataset.root!r} for class(es) {missing}.")
xn, mu, sd = _standardize(x)
centroids = np.stack([xn[y == c].mean(axis=0) for c in range(k)])
# nearest-centroid train accuracy
dists = np.linalg.norm(xn[:, None, :] - centroids[None, :, :], axis=2)
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8 changes: 8 additions & 0 deletions tests/test_downstream_agents.py
Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,14 @@ def _ref(**kw) -> DatasetRef:
return DatasetRef(**base)


def test_centroid_train_rejects_class_without_samples(tmp_path: Path):
ds = _make_dataset(tmp_path)
ds = ds.model_copy(update={"class_names": [*ds.class_names, "c"]})
with pytest.raises(RuntimeError, match=r"class\(es\) \['c'\]"):
CentroidTrainBackend(output_root=str(tmp_path / "models")).train(ds, _arch(), _cfg())
assert not (tmp_path / "models").exists()


def test_real_backends_chain(tmp_path: Path):
ds = _make_dataset(tmp_path)
tr = CentroidTrainBackend(output_root=str(tmp_path / "models")).train(ds, _arch(), _cfg())
Expand Down