Enhance compute_reframe() to process data by chunks to prevent joblib…

… deadlocks on Apple Silicon

pygmtsar/pygmtsar/Stack_reframe.py

@@ -140,7 +140,7 @@ def _reframe_subswath(self, subswath, date, geometry, debug=False):
                                       if geom.intersects(geometry)])
         return out
 
-    def compute_reframe(self, geometry=None, n_jobs=-1, **kwargs):
+    def compute_reframe(self, geometry=None, n_jobs=-1, queue=16, caption='Reframing', **kwargs):
         """
         Reorder bursts from sequential scenes to cover the full orbit area or some bursts only.
 
@@ -174,21 +174,46 @@ def compute_reframe(self, geometry=None, n_jobs=-1, **kwargs):
         import joblib
         import pandas as pd
 
+        if n_jobs is None or ('debug' in kwargs and kwargs['debug'] == True):
+            print ('Note: sequential joblib processing is applied when "n_jobs" is None or "debug" is True.')
+            joblib_backend = 'sequential'
+        else:
+            joblib_backend = 'loky'
+
         dates = self.df.index.unique().values
         subswaths = self.get_subswaths()
         # approximate subswath geometries from GCP
         geometries = {subswath: self.df[self.df.subswath==subswath].geometry.unary_union for subswath in subswaths}
 
-        # process all the scenes
-        if n_jobs is None or ('debug' in kwargs and kwargs['debug'] == True):
-            print ('Note: sequential joblib processing is applied when "n_jobs" is None or "debug" is True.')
-            joblib_backend = 'sequential'
+        records = []
+        # Applying iterative processing to prevent Dask scheduler deadlocks.
+        stacksize = len(dates)
+        counter = 0
+        digits = len(str(stacksize))
+        # Splitting all the pairs into chunks, each containing approximately queue pairs.
+        #n_chunks = stacksize // queue if stacksize > queue else 1
+        if stacksize > queue:
+            chunks = [dates[i:i + queue] for i in range(0, stacksize, queue)]
+            n_chunks = len(chunks)
         else:
-            joblib_backend = None
-        with self.tqdm_joblib(tqdm(desc='Reframing', total=len(dates)*len(subswaths))) as progress_bar:
-            records = joblib.Parallel(n_jobs=n_jobs, backend=joblib_backend)(joblib.delayed(self._reframe_subswath)\
-                            (subswath, date,
-                            geometry.intersection(geometries[subswath]) if geometry is not None else geometries[subswath],
-                            **kwargs) for date in dates for subswath in subswaths)
+            chunks = [pairs]
+            n_chunks = 1
+        for chunk in chunks:
+            if n_chunks > 1:
+                chunk_caption = f'{caption}: {(counter+1):0{digits}}...{(counter+len(chunk)):0{digits}} from {stacksize}'
+            else:
+                chunk_caption = caption
+
+            if joblib_backend == 'loky':
+                # can be missed on some systems
+                from joblib.externals import loky
+                loky.get_reusable_executor(kill_workers=True).shutdown(wait=True)
+            with self.tqdm_joblib(tqdm(desc=chunk_caption, total=len(chunk)*len(subswaths))) as progress_bar:
+                chunk_records = joblib.Parallel(n_jobs=n_jobs, backend=joblib_backend)(joblib.delayed(self._reframe_subswath)\
+                                (subswath, date,
+                                geometry.intersection(geometries[subswath]) if geometry is not None else geometries[subswath],
+                                **kwargs) for date in chunk for subswath in subswaths)
+                records.extend(chunk_records)
+            counter += len(chunk)
 
         self.df = pd.concat(records)