fix: address review comments on aggregate_sample_features refactor

mussel/cli/aggregate_sample_features.py

@@ -126,24 +126,32 @@ def main(cfg: AggregateSampleFeaturesConfig):
             f"sample_ids ({len(sample_ids)}) must have the same length."
         )
 
-    features_list = []
-    coords_list = []
-    for h5_path in patch_features_h5_paths:
-        with h5py.File(h5_path, "r") as h5:
-            features_list.append(np.array(h5["features"]))
-            coords_list.append(h5["coords"][:])
-
-    results = aggregate_sample_features(
-        features_list=features_list,
-        coords_list=coords_list,
-        sample_ids=sample_ids,
-        max_tiles=cfg.max_tiles,
-        subsampling_strategy=cfg.subsampling_strategy,
-        seed=cfg.seed,
-    )
+    # Group indices by sample_id first so we only hold one sample's slides in
+    # memory at a time, keeping peak memory proportional to the largest sample
+    # rather than the entire input set.
+    groups: dict[str, list[int]] = {}
+    for idx, sid in enumerate(sample_ids):
+        groups.setdefault(sid, []).append(idx)
 
     os.makedirs(cfg.output_dir, exist_ok=True)
-    for sample_id, (features, coords) in results.items():
+    for sample_id, indices in groups.items():
+        features_list = []
+        coords_list = []
+        for i in indices:
+            with h5py.File(patch_features_h5_paths[i], "r") as h5:
+                features_list.append(np.array(h5["features"]))
+                coords_list.append(h5["coords"][:])
+
+        result = aggregate_sample_features(
+            features_list=features_list,
+            coords_list=coords_list,
+            sample_ids=[sample_id] * len(indices),
+            max_tiles=cfg.max_tiles,
+            subsampling_strategy=cfg.subsampling_strategy,
+            seed=cfg.seed,
+        )
+
+        features, coords = result[sample_id]
         out_h5 = os.path.join(cfg.output_dir, f"{sample_id}.{cfg.output_h5_suffix}")
         save_hdf5(out_h5, {"features": features, "coords": coords}, mode="w")
         logger.info(

mussel/utils/feature_extract.py

@@ -1937,7 +1937,7 @@ def aggregate_sample_features(
     max_tiles: Optional[int] = None,
     subsampling_strategy: str = "random",
     seed: int = 42,
-) -> dict:
+) -> dict[str, tuple[np.ndarray, np.ndarray]]:
     """Concatenate per-slide patch features into one array per sample.
 
     Groups slides by ``sample_id``, concatenates their features and coordinates
@@ -1968,11 +1968,29 @@ def aggregate_sample_features(
             f"and sample_ids ({len(sample_ids)}) must all have the same length."
         )
 
-    groups: dict = collections.OrderedDict()
+    for i, (feats, coords) in enumerate(zip(features_list, coords_list)):
+        sid = sample_ids[i]
+        if feats.ndim != 2:
+            raise ValueError(
+                f"features_list[{i}] (sample_id={sid!r}) must be 2-D, "
+                f"got shape {feats.shape}."
+            )
+        if coords.ndim != 2 or coords.shape[1] != 2:
+            raise ValueError(
+                f"coords_list[{i}] (sample_id={sid!r}) must have shape (N, 2), "
+                f"got shape {coords.shape}."
+            )
+        if len(feats) != len(coords):
+            raise ValueError(
+                f"features_list[{i}] and coords_list[{i}] (sample_id={sid!r}) "
+                f"have different lengths: {len(feats)} vs {len(coords)}."
+            )
+
+    groups: dict[str, list[int]] = {}
     for idx, sid in enumerate(sample_ids):
         groups.setdefault(sid, []).append(idx)
 
-    results: dict = collections.OrderedDict()
+    results: dict[str, tuple[np.ndarray, np.ndarray]] = {}
 
     for sample_id, indices in groups.items():
         logger.info("Aggregating sample %s from %d slide(s)", sample_id, len(indices))

tests/mussel/cli/test_aggregate_sample_features.py

@@ -124,6 +124,35 @@ def test_subsample_tiles_invalid_strategy():
     aggregate_sample_features as _aggregate_sample_features
 
 
+def test_aggregate_sample_features_invalid_shapes():
+    """Per-slide validation raises informative ValueError on bad input."""
+    feats, coords = _make_data(10)
+
+    # 1-D features array
+    with pytest.raises(ValueError, match="2-D"):
+        _aggregate_sample_features(
+            features_list=[feats.ravel()],
+            coords_list=[coords],
+            sample_ids=["s"],
+        )
+
+    # coords wrong second dim
+    with pytest.raises(ValueError, match=r"\(N, 2\)"):
+        _aggregate_sample_features(
+            features_list=[feats],
+            coords_list=[coords[:, :1]],
+            sample_ids=["s"],
+        )
+
+    # mismatched lengths
+    with pytest.raises(ValueError, match="different lengths"):
+        _aggregate_sample_features(
+            features_list=[feats],
+            coords_list=[coords[:5]],
+            sample_ids=["s"],
+        )
+
+
 def test_aggregate_sample_features_single_slide(tmp_path):
     """One slide per sample — output equals input."""
     feats_a, coords_a = _make_data(30)
@@ -159,6 +188,12 @@ def test_aggregate_sample_features_multi_slide(tmp_path):
 
     assert results["sampleX"][0].shape == (35, 4)
     assert results["sampleX"][1].shape == (35, 2)
+    np.testing.assert_array_equal(
+        results["sampleX"][0], np.concatenate([feats_a, feats_b], axis=0)
+    )
+    np.testing.assert_array_equal(
+        results["sampleX"][1], np.concatenate([coords_a, coords_b], axis=0)
+    )
 
 
 def test_aggregate_sample_features_save_pt_false(tmp_path):
@@ -197,23 +232,39 @@ def test_aggregate_sample_features_two_samples(tmp_path):
 
 
 def test_aggregate_sample_features_with_subsampling(tmp_path):
-    """Subsampling reduces output to max_tiles."""
-    rng = np.random.default_rng(0)
-    feats_a = rng.random((80, 4)).astype(np.float32)
-    coords_a = rng.integers(0, 1000, (80, 2))
-    feats_b = rng.random((60, 4)).astype(np.float32)
-    coords_b = rng.integers(0, 1000, (60, 2))
+    """Subsampling reduces output to max_tiles, is reproducible, and keeps features/coords aligned."""
+    # Use identifiable rows: feature row i has value i in all dims, coord row i
+    # is (i, i). After subsampling, each selected feature row must equal its
+    # corresponding coord row, proving the two arrays stay in sync.
+    n_a, n_b = 80, 60
+    feats_a = np.tile(np.arange(n_a, dtype=np.float32)[:, None], (1, 4))
+    coords_a = np.tile(np.arange(n_a)[:, None], (1, 2))
+    feats_b = np.tile(np.arange(n_a, n_a + n_b, dtype=np.float32)[:, None], (1, 4))
+    coords_b = np.tile(np.arange(n_a, n_a + n_b)[:, None], (1, 2))
+
+    def run():
+        return _aggregate_sample_features(
+            features_list=[feats_a, feats_b],
+            coords_list=[coords_a, coords_b],
+            sample_ids=["big", "big"],
+            max_tiles=50,
+            subsampling_strategy="random",
+            seed=99,
+        )
 
-    results = _aggregate_sample_features(
-        features_list=[feats_a, feats_b],
-        coords_list=[coords_a, coords_b],
-        sample_ids=["big", "big"],
-        max_tiles=50,
-        subsampling_strategy="random",
-        seed=99,
-    )
+    r1 = run()
+    r2 = run()
+    f_out, c_out = r1["big"]
+
+    assert f_out.shape[0] == 50
+    assert c_out.shape[0] == 50
+
+    # Reproducible with same seed
+    np.testing.assert_array_equal(r1["big"][0], r2["big"][0])
+    np.testing.assert_array_equal(r1["big"][1], r2["big"][1])
 
-    assert results["big"][0].shape[0] == 50
+    # features and coords remain aligned: feature value == coord value for each row
+    np.testing.assert_array_equal(f_out[:, 0].astype(np.int64), c_out[:, 0])
 
 
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