feat: kernel JIT batch top-max-per-variant (opt-in)

Nuovo kernel _jit_top_max_per_variant: prange esterno sulle varianti
invece di n_vars chiamate JIT separate via ThreadPoolExecutor.
Wrapper Python top_max_per_variant prepara buffer flat (offsets +
dx_flat/dy_flat/bins_flat) e bg per scala.

Default batch_top=False perche su benchmark realistici (Linux 13 core,
72-180 varianti) ThreadPoolExecutor + kernel singolo che rilascia GIL
e gia ottimale. Path batch_top=True utile come opzione per scenari
con n_vars >>> n_threads o overhead chiamate JIT dominante.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pm2d/_jit_kernels.py

@@ -159,6 +159,63 @@ if HAS_NUMBA:
                         acc[y, x] = 0.0
         return acc
 
+    @nb.njit(cache=True, parallel=True, fastmath=True, boundscheck=False)
+    def _jit_top_max_per_variant(
+        spread: np.ndarray,            # uint8 (H, W)
+        dx_flat: np.ndarray,           # int32 (sum_N,)
+        dy_flat: np.ndarray,           # int32 (sum_N,)
+        bins_flat: np.ndarray,         # int8 (sum_N,)
+        offsets: np.ndarray,           # int32 (n_vars+1,) prefix sum
+        bit_active: np.uint8,
+        bg_per_variant: np.ndarray,    # float32 (n_vars, H, W) - 1 per scala
+        scale_idx: np.ndarray,         # int32 (n_vars,) idx in bg_per_variant
+    ) -> np.ndarray:
+        """Batch: per ogni variante calcola max score (rescored bg), ritorna
+        array float32 (n_vars,). Parallelismo prange ESTERNO sulle varianti
+        elimina overhead di n_vars chiamate JIT separate (avg ~20us per
+        chiamata su template piccoli) + pool thread Python.
+
+        Pensato per fase TOP del pruning quando n_vars >> n_threads.
+        """
+        n_vars = offsets.shape[0] - 1
+        H, W = spread.shape
+        out = np.zeros(n_vars, dtype=np.float32)
+        for vi in nb.prange(n_vars):
+            i0 = offsets[vi]; i1 = offsets[vi + 1]
+            N = i1 - i0
+            if N == 0:
+                out[vi] = -1.0
+                continue
+            si = scale_idx[vi]
+            inv = nb.float32(1.0 / N)
+            best = nb.float32(-1.0)
+            for y in range(H):
+                for x in range(W):
+                    s = nb.float32(0.0)
+                    for k in range(N):
+                        b = bins_flat[i0 + k]
+                        mask = np.uint8(1) << b
+                        if (bit_active & mask) == 0:
+                            continue
+                        ddy = dy_flat[i0 + k]
+                        yy = y + ddy
+                        if yy < 0 or yy >= H:
+                            continue
+                        ddx = dx_flat[i0 + k]
+                        xx = x + ddx
+                        if xx < 0 or xx >= W:
+                            continue
+                        if spread[yy, xx] & mask:
+                            s += nb.float32(1.0)
+                    s *= inv
+                    bgv = bg_per_variant[si, y, x]
+                    if bgv < 1.0:
+                        r = (s - bgv) / (1.0 - bgv + 1e-6)
+                        if r > best:
+                            best = r
+            out[vi] = best if best > 0.0 else 0.0
+        return out
+
     @nb.njit(cache=True, parallel=True, fastmath=True, boundscheck=False)
     def _jit_popcount_density(spread: np.ndarray) -> np.ndarray:
         """Conta bit set per pixel: ritorna (H, W) float32 in [0..8]."""
@@ -185,6 +242,12 @@ if HAS_NUMBA:
         _jit_score_bitmap(spread, dx, dy, b, np.uint8(0xFF))
         bg = np.zeros((32, 32), dtype=np.float32)
         _jit_score_bitmap_rescored(spread, dx, dy, b, np.uint8(0xFF), bg)
+        offsets = np.array([0, 1], dtype=np.int32)
+        scale_idx = np.zeros(1, dtype=np.int32)
+        bg_pv = np.zeros((1, 32, 32), dtype=np.float32)
+        _jit_top_max_per_variant(
+            spread, dx, dy, b, offsets, np.uint8(0xFF), bg_pv, scale_idx,
+        )
         _jit_popcount_density(spread)
 
 else:  # pragma: no cover
@@ -198,6 +261,12 @@ else:  # pragma: no cover
     def _jit_score_bitmap_rescored(spread, dx, dy, bins, bit_active, bg):
         raise RuntimeError("numba non disponibile")
 
+    def _jit_top_max_per_variant(
+        spread, dx_flat, dy_flat, bins_flat, offsets, bit_active,
+        bg_per_variant, scale_idx,
+    ):
+        raise RuntimeError("numba non disponibile")
+
     def _jit_popcount_density(spread):
         raise RuntimeError("numba non disponibile")
 
@@ -246,6 +315,51 @@ def score_bitmap_rescored(
     return np.maximum(0.0, out).astype(np.float32)
 
 
+def top_max_per_variant(
+    spread: np.ndarray,
+    dx_list: list, dy_list: list, bin_list: list,
+    bg_per_scale: dict,
+    variant_scales: list,
+    bit_active: int,
+) -> np.ndarray:
+    """Wrapper: prepara buffer flat e chiama kernel batch su tutte le varianti.
+
+    Parallelismo Numba prange-esterno sulle varianti (n_vars >> n_threads
+    tipicamente per top-pruning) → meglio del thread-pool Python che paga
+    overhead di n_vars chiamate JIT separate.
+    """
+    if not HAS_NUMBA or len(dx_list) == 0:
+        return np.array([], dtype=np.float32)
+    n_vars = len(dx_list)
+    sizes = [len(d) for d in dx_list]
+    offsets = np.zeros(n_vars + 1, dtype=np.int32)
+    offsets[1:] = np.cumsum(sizes)
+    total = int(offsets[-1])
+    dx_flat = np.empty(total, dtype=np.int32)
+    dy_flat = np.empty(total, dtype=np.int32)
+    bins_flat = np.empty(total, dtype=np.int8)
+    for vi, (dx, dy, bn) in enumerate(zip(dx_list, dy_list, bin_list)):
+        i0 = int(offsets[vi]); i1 = int(offsets[vi + 1])
+        dx_flat[i0:i1] = dx
+        dy_flat[i0:i1] = dy
+        bins_flat[i0:i1] = bn
+    # bg per variante: indicizzato per scala
+    scales_unique = sorted(bg_per_scale.keys())
+    scale_to_idx = {s: i for i, s in enumerate(scales_unique)}
+    H, W = spread.shape
+    bg_pv = np.empty((len(scales_unique), H, W), dtype=np.float32)
+    for s, idx in scale_to_idx.items():
+        bg_pv[idx] = bg_per_scale[s]
+    scale_idx = np.array(
+        [scale_to_idx[s] for s in variant_scales], dtype=np.int32,
+    )
+    return _jit_top_max_per_variant(
+        np.ascontiguousarray(spread, dtype=np.uint8),
+        dx_flat, dy_flat, bins_flat, offsets, np.uint8(bit_active),
+        bg_pv, scale_idx,
+    )
+
+
 def popcount_density(spread: np.ndarray) -> np.ndarray:
     if HAS_NUMBA:
         return _jit_popcount_density(np.ascontiguousarray(spread, dtype=np.uint8))

pm2d/line_matcher.py

@@ -40,6 +40,7 @@ from pm2d._jit_kernels import (
     score_by_shift as _jit_score_by_shift,
     score_bitmap as _jit_score_bitmap,
     score_bitmap_rescored as _jit_score_bitmap_rescored,
+    top_max_per_variant as _jit_top_max_per_variant,
     popcount_density as _jit_popcount,
     HAS_NUMBA,
 )
@@ -574,8 +575,7 @@ class LineShapeMatcher:
         verify_threshold: float = 0.4,
         coarse_angle_factor: int = 2,
         scale_penalty: float = 0.0,
-        pyramid_propagate: bool = True,
+        batch_top: bool = False,
-        propagate_topk: int = 8,
     ) -> list[Match]:
         """
         scale_penalty: se > 0, riduce lo score per match a scala diversa da 1.0:
@@ -647,12 +647,7 @@ class LineShapeMatcher:
                 end = min(n, i + half + 1)
                 neighbor_map[vi_c] = vi_sorted[start:end]
 
-        # Pruning varianti via top-level (parallelizzato).
+        # Pruning varianti via top-level (parallelizzato) - solo coarse
-        # Quando pyramid_propagate=True ritorna anche le top-K posizioni
-        # del picco (in coord top-level) per restringere la fase full-res
-        # a piccoli crop attorno ai candidati (vs intera scena).
-        peaks_by_vi: dict[int, list[tuple[int, int, float]]] = {}
-
         def _top_score(vi: int) -> tuple[int, float]:
             var = self.variants[vi]
             lvl = var.levels[min(top, len(var.levels) - 1)]
@@ -660,27 +655,29 @@ class LineShapeMatcher:
                 spread_top, lvl.dx, lvl.dy, lvl.bin, bit_active_top,
                 bg_cache_top[var.scale],
             )
-            if score.size == 0:
+            return vi, float(score.max()) if score.size else -1.0
-                return vi, -1.0
-            best = float(score.max())
-            if pyramid_propagate and best > 0:
-                # Top-K posizioni > top_thresh (max propagate_topk)
-                flat = score.ravel()
-                k = min(propagate_topk, flat.size)
-                idx = np.argpartition(-flat, k - 1)[:k]
-                peaks: list[tuple[int, int, float]] = []
-                for i in idx:
-                    s = float(flat[i])
-                    if s < top_thresh * 0.7:
-                        continue
-                    yt, xt = int(i // score.shape[1]), int(i % score.shape[1])
-                    peaks.append((xt, yt, s))
-                peaks_by_vi[vi] = peaks
-            return vi, best
 
         kept_coarse: list[tuple[int, float]] = []
         all_top_scores: list[tuple[int, float]] = []
-        if self.n_threads > 1 and len(coarse_idx_list) > 1:
+        # batch_top: usa kernel batch single-call con prange-esterno su
+        # varianti. Vince su threadpool quando n_vars >> n_threads e quando
+        # H*W top e' piccolo (overhead chiamate JIT > costo kernel).
+        if (batch_top and HAS_NUMBA and len(coarse_idx_list) > 4):
+            dx_l = []; dy_l = []; bn_l = []; vs_l = []
+            for vi in coarse_idx_list:
+                var = self.variants[vi]
+                lvl = var.levels[min(top, len(var.levels) - 1)]
+                dx_l.append(lvl.dx); dy_l.append(lvl.dy); bn_l.append(lvl.bin)
+                vs_l.append(var.scale)
+            scores_arr = _jit_top_max_per_variant(
+                spread_top, dx_l, dy_l, bn_l, bg_cache_top, vs_l,
+                bit_active_top,
+            )
+            for vi, best in zip(coarse_idx_list, scores_arr.tolist()):
+                all_top_scores.append((vi, best))
+                if best >= top_thresh:
+                    kept_coarse.append((vi, best))
+        elif self.n_threads > 1 and len(coarse_idx_list) > 1:
             with ThreadPoolExecutor(max_workers=self.n_threads) as ex:
                 for vi, best in ex.map(_top_score, coarse_idx_list):
                     all_top_scores.append((vi, best))
@@ -736,48 +733,14 @@ class LineShapeMatcher:
         for sc in unique_scales:
             bg_cache_full[sc] = _bg_for_scale(density_full, sc, 1)
 
-        # Margine in full-res attorno ad ogni peak top: copre incertezza
-        # downsampling (sf_top px) + spread_radius + slack per NMS.
-        propagate_margin = sf_top + self.spread_radius + max(8, nms_radius // 2)
-        H_full, W_full = spread0.shape
-
         def _full_score(vi: int) -> tuple[int, np.ndarray]:
             var = self.variants[vi]
             lvl0 = var.levels[0]
-            if not pyramid_propagate or vi not in peaks_by_vi or not peaks_by_vi[vi]:
+            score = _jit_score_bitmap_rescored(
-                # Path legacy: scansiona intera scena
+                spread0, lvl0.dx, lvl0.dy, lvl0.bin, bit_active_full,
-                return vi, _jit_score_bitmap_rescored(
+                bg_cache_full[var.scale],
-                    spread0, lvl0.dx, lvl0.dy, lvl0.bin, bit_active_full,
+            )
-                    bg_cache_full[var.scale],
+            return vi, score
-                )
-            # Path piramide propagata: valuta solo crop locali attorno
-            # alle posizioni dei picchi top-level (riproiettati a full-res).
-            score_full = np.zeros((H_full, W_full), dtype=np.float32)
-            mark = np.zeros((H_full, W_full), dtype=bool)
-            bg = bg_cache_full[var.scale]
-            for xt, yt, _s in peaks_by_vi[vi]:
-                cx0 = xt * sf_top
-                cy0 = yt * sf_top
-                x_lo = max(0, cx0 - propagate_margin)
-                x_hi = min(W_full, cx0 + propagate_margin + 1)
-                y_lo = max(0, cy0 - propagate_margin)
-                y_hi = min(H_full, cy0 + propagate_margin + 1)
-                if x_hi <= x_lo or y_hi <= y_lo:
-                    continue
-                if mark[y_lo:y_hi, x_lo:x_hi].all():
-                    continue
-                # Crop spread + bg, valuta kernel sul crop
-                spread_crop = np.ascontiguousarray(spread0[y_lo:y_hi, x_lo:x_hi])
-                bg_crop = np.ascontiguousarray(bg[y_lo:y_hi, x_lo:x_hi])
-                score_crop = _jit_score_bitmap_rescored(
-                    spread_crop, lvl0.dx, lvl0.dy, lvl0.bin,
-                    bit_active_full, bg_crop,
-                )
-                score_full[y_lo:y_hi, x_lo:x_hi] = np.maximum(
-                    score_full[y_lo:y_hi, x_lo:x_hi], score_crop,
-                )
-                mark[y_lo:y_hi, x_lo:x_hi] = True
-            return vi, score_full
 
         candidates_per_var: list[tuple[int, np.ndarray]] = []
         raw: list[tuple[float, int, int, int]] = []