Parallelize AIS post-processing (#851)

micro_sam/automatic_segmentation.py

@@ -120,7 +120,11 @@ def automatic_instance_segmentation(
             verbose=verbose,
         )
 
-        segmenter.initialize(image=image_data, image_embeddings=image_embeddings)
+        # If we run AIS with tiling then we use the same tile shape for the watershed postprocessing.
+        if isinstance(segmenter, InstanceSegmentationWithDecoder) and tile_shape is not None:
+            generate_kwargs.update({"tile_shape": tile_shape, "halo": halo})
+
+        segmenter.initialize(image=image_data, image_embeddings=image_embeddings, verbose=verbose)
         masks = segmenter.generate(**generate_kwargs)
 
         if len(masks) == 0:  # instance segmentation can have no masks, hence we just save empty labels

micro_sam/instance_segmentation.py

@@ -12,6 +12,8 @@
 
 import vigra
 import numpy as np
+import elf.parallel as parallel
+from elf.parallel.filters import apply_filter
 from skimage.measure import label, regionprops
 from skimage.segmentation import relabel_sequential
 
@@ -559,11 +561,13 @@ def generate(
 
 
 # Helper function for tiled embedding computation and checking consistent state.
-def _process_tiled_embeddings(predictor, image, image_embeddings, tile_shape, halo):
+def _process_tiled_embeddings(predictor, image, image_embeddings, tile_shape, halo, verbose):
     if image_embeddings is None:
         if tile_shape is None or halo is None:
             raise ValueError("To compute tiled embeddings the parameters tile_shape and halo have to be passed.")
-        image_embeddings = util.precompute_image_embeddings(predictor, image, tile_shape=tile_shape, halo=halo)
+        image_embeddings = util.precompute_image_embeddings(
+            predictor, image, tile_shape=tile_shape, halo=halo, verbose=verbose
+        )
 
     # Use tile shape and halo from the precomputed embeddings if not given.
     # Otherwise check that they are consistent.
@@ -650,7 +654,7 @@ def initialize(
         self._original_size = original_size
 
         image_embeddings, tile_shape, halo = _process_tiled_embeddings(
-            self._predictor, image, image_embeddings, tile_shape, halo
+            self._predictor, image, image_embeddings, tile_shape, halo, verbose=verbose,
         )
 
         tiling = blocking([0, 0], original_size, tile_shape)
@@ -853,6 +857,55 @@ def get_predictor_and_decoder(
     return predictor, decoder
 
 
+def _watershed_from_center_and_boundary_distances_parallel(
+    center_distances,
+    boundary_distances,
+    foreground_map,
+    center_distance_threshold,
+    boundary_distance_threshold,
+    foreground_threshold,
+    distance_smoothing,
+    min_size,
+    tile_shape,
+    halo,
+    n_threads,
+    verbose=False,
+):
+    center_distances = apply_filter(
+        center_distances, "gaussianSmoothing", sigma=distance_smoothing,
+        block_shape=tile_shape, n_threads=n_threads
+    )
+    boundary_distances = apply_filter(
+        boundary_distances, "gaussianSmoothing", sigma=distance_smoothing,
+        block_shape=tile_shape, n_threads=n_threads
+    )
+
+    fg_mask = foreground_map > foreground_threshold
+
+    marker_map = np.logical_and(
+        center_distances < center_distance_threshold, boundary_distances < boundary_distance_threshold
+    )
+    marker_map[~fg_mask] = 0
+
+    markers = np.zeros(marker_map.shape, dtype="uint64")
+    markers = parallel.label(
+        marker_map, out=markers, block_shape=tile_shape, n_threads=n_threads, verbose=verbose,
+    )
+
+    seg = np.zeros_like(markers, dtype="uint64")
+    seg = parallel.seeded_watershed(
+        boundary_distances, seeds=markers, out=seg, block_shape=tile_shape,
+        halo=halo, n_threads=n_threads, verbose=verbose, mask=fg_mask,
+    )
+
+    out = np.zeros_like(seg, dtype="uint64")
+    out = parallel.size_filter(
+        seg, out=out, min_size=min_size, block_shape=tile_shape, n_threads=n_threads, verbose=verbose
+    )
+
+    return out
+
+
 class InstanceSegmentationWithDecoder:
     """Generates an instance segmentation without prompts, using a decoder.
 
@@ -988,6 +1041,9 @@ def generate(
         distance_smoothing: float = 1.6,
         min_size: int = 0,
         output_mode: Optional[str] = "binary_mask",
+        tile_shape: Optional[Tuple[int, int]] = None,
+        halo: Optional[Tuple[int, int]] = None,
+        n_threads: Optional[int] = None,
     ) -> List[Dict[str, Any]]:
         """Generate instance segmentation for the currently initialized image.
 
@@ -1002,6 +1058,11 @@ def generate(
             distance_smoothing: Sigma value for smoothing the distance predictions.
             min_size: Minimal object size in the segmentation result.
             output_mode: The form masks are returned in. Pass None to directly return the instance segmentation.
+            tile_shape: Tile shape for parallelizing the instance segmentation post-processing.
+                This parameter is independent from the tile shape for computing the embeddings.
+                If not given then post-processing will not be parallelized.
+            halo: Halo for parallel post-processing. See also `tile_shape`.
+            n_threads: Number of threads for parallel post-processing. See also `tile_shape`.
 
         Returns:
             The instance segmentation masks.
@@ -1013,16 +1074,29 @@ def generate(
             foreground = vigra.filters.gaussianSmoothing(self._foreground, foreground_smoothing)
         else:
             foreground = self._foreground
-        # Further optimization: parallel implementation using elf.parallel functionality.
-        # (Make sure to expose n_threads to avoid over-subscription in case of outer parallelization)
-        segmentation = watershed_from_center_and_boundary_distances(
-            self._center_distances, self._boundary_distances, foreground,
-            center_distance_threshold=center_distance_threshold,
-            boundary_distance_threshold=boundary_distance_threshold,
-            foreground_threshold=foreground_threshold,
-            distance_smoothing=distance_smoothing,
-            min_size=min_size,
-        )
+
+        if tile_shape is None:
+            segmentation = watershed_from_center_and_boundary_distances(
+                self._center_distances, self._boundary_distances, foreground,
+                center_distance_threshold=center_distance_threshold,
+                boundary_distance_threshold=boundary_distance_threshold,
+                foreground_threshold=foreground_threshold,
+                distance_smoothing=distance_smoothing,
+                min_size=min_size,
+            )
+        else:
+            if halo is None:
+                raise ValueError("You must pass a value for halo if tile_shape is given.")
+            segmentation = _watershed_from_center_and_boundary_distances_parallel(
+                self._center_distances, self._boundary_distances, foreground,
+                center_distance_threshold=center_distance_threshold,
+                boundary_distance_threshold=boundary_distance_threshold,
+                foreground_threshold=foreground_threshold,
+                distance_smoothing=distance_smoothing,
+                min_size=min_size, tile_shape=tile_shape,
+                halo=halo, n_threads=n_threads, verbose=False,
+            )
+
         if output_mode is not None:
             segmentation = self._to_masks(segmentation, output_mode)
         return segmentation
@@ -1094,7 +1168,7 @@ def initialize(
         """
         original_size = image.shape[:2]
         image_embeddings, tile_shape, halo = _process_tiled_embeddings(
-            self._predictor, image, image_embeddings, tile_shape, halo
+            self._predictor, image, image_embeddings, tile_shape, halo, verbose=verbose,
         )
         tiling = blocking([0, 0], original_size, tile_shape)
 
@@ -1127,6 +1201,8 @@ def initialize(
             foreground[inner_bb] = output[0][local_bb]
             center_distances[inner_bb] = output[1][local_bb]
             boundary_distances[inner_bb] = output[2][local_bb]
+            pbar_update(1)
+
         pbar_close()
 
         # Set the state.