model_zoo: fix clash between Predictor and direct (OCR) use-cases…

- `load_models()`: uniformly handle arg types
- `load_model()`: move handling of non-model categories
  to `load_models()`
- `load_model()`: move SavedModel preference over HDF5 to `model_path()`
- `_load_ocr_model()`: add user-selected device handling and reporting
  for Torch (as for TF)
- `_load_ocr_model()`: move (TF-based) CNN-RNN case to `load_model()`
  (including Keras layer mapping)
- `shutdown()`: only apply `shutdown()` to Predictor model types

src/eynollah/model_zoo/model_zoo.py

@@ -70,6 +70,9 @@ class EynollahModelZoo:
             model_path = Path(self.model_basedir).joinpath(spec.filename)
         else:
             model_path = Path(spec.filename)
+        if model_path.suffix == '.h5' and Path(model_path.stem).exists():
+            # prefer SavedModel over HDF5 format if it exists
+            model_path = Path(model_path.stem)
         return model_path
 
     def load_models(
@@ -82,20 +85,42 @@ class EynollahModelZoo:
         """
         ret = {} # cannot use self._loaded here, yet – first spawn all predictors
         for load_args in all_load_args:
+            load_kwargs = dict(device=device)
             if isinstance(load_args, str):
-                model_category = load_args
-                load_args = [model_category]
+                model_category, model_variant = load_args, ""
+            elif len(load_args) > 2:
+                # for calls to self.model_path
+                self.override_models(load_args)
+                # for calls to Predictor.load_model
+                model_category, model_variant, model_path = load_args
+                load_kwargs["model_variant"] = model_variant
+                load_kwargs["model_path_override"] = model_path
             else:
-                model_category = load_args[0]
-            load_kwargs = {}
+                model_category, model_variant = load_args
+                load_kwargs["model_variant"] = model_variant
+
             if model_category.endswith('_resized'):
-                load_args[0] = model_category[:-8]
+                model_category = model_category[:-8]
                 load_kwargs["resized"] = True
             elif model_category.endswith('_patched'):
-                load_args[0] = model_category[:-8]
+                model_category = model_category[:-8]
                 load_kwargs["patched"] = True
-            ret[model_category] = Predictor(self.logger, self)
-            ret[model_category].load_model(*load_args, **load_kwargs, device=device)
+
+            if model_category == 'ocr':
+                model = self._load_ocr_model(variant=model_variant, device=device)
+            elif model_category == 'num_to_char':
+                model = self._load_num_to_char()
+            elif model_category == 'characters':
+                model = self._load_characters()
+            elif model_category == 'trocr_processor':
+                from transformers import TrOCRProcessor
+                model_path = self.model_path(model_category, model_variant)
+                model = TrOCRProcessor.from_pretrained(model_path)
+            else:
+                model = Predictor(self.logger, self)
+                model.load_model(model_category, **load_kwargs)
+
+            ret[model_category] = model
         self._loaded.update(ret)
         return self._loaded
 
@@ -117,6 +142,7 @@ class EynollahModelZoo:
 
         import tensorflow as tf
         from tensorflow.keras.models import load_model
+        from tensorflow.keras.models import Model as KerasModel
 
         from ..patch_encoder import (
             PatchEncoder,
@@ -162,19 +188,6 @@ class EynollahModelZoo:
         if model_path_override:
             self.override_models((model_category, model_variant, model_path_override))
         model_path = self.model_path(model_category, model_variant)
-        if model_path.suffix == '.h5' and Path(model_path.stem).exists():
-            # prefer SavedModel over HDF5 format if it exists
-            model_path = Path(model_path.stem)
-        if model_category == 'ocr':
-            model = self._load_ocr_model(variant=model_variant)
-        elif model_category == 'num_to_char':
-            model = self._load_num_to_char()
-        elif model_category == 'characters':
-            model = self._load_characters()
-        elif model_category == 'trocr_processor':
-            from transformers import TrOCRProcessor
-            model = TrOCRProcessor.from_pretrained(model_path)
-        else:
         try:
             # avoid wasting VRAM on non-transformer models
             model = load_model(model_path, compile=False)
@@ -184,6 +197,7 @@ class EynollahModelZoo:
                 model_path, compile=False,
                 custom_objects=dict(PatchEncoder=PatchEncoder,
                                     Patches=Patches))
+        assert isinstance(model, KerasModel)
         model._name = model_category
         if resized:
             model = wrap_layout_model_resized(model)
@@ -193,6 +207,13 @@ class EynollahModelZoo:
             model._name = model_category + '_patched'
         else:
             model.jit_compile = True
+
+        if model_category == 'ocr':
+            model = KerasModel(
+                model.get_layer(name="image").input,   # type: ignore
+                model.get_layer(name="dense2").output, # type: ignore
+        )
+
         model.make_predict_function()
         return model
 
@@ -201,26 +222,34 @@ class EynollahModelZoo:
             raise ValueError(f'Model "{model_category}" not previously loaded with "load_model(..)"')
         return self._loaded[model_category]
 
-    def _load_ocr_model(self, variant: str) -> AnyModel:
+    def _load_ocr_model(self, variant: str, device: str = "") -> AnyModel:
         """
         Load OCR model
         """
-        from tensorflow.keras.models import Model as KerasModel
-        from tensorflow.keras.models import load_model
-
-        ocr_model_dir = self.model_path('ocr', variant)
+        model_dir = self.model_path('ocr', variant)
         if variant == 'tr':
             from transformers import VisionEncoderDecoderModel
-            ret = VisionEncoderDecoderModel.from_pretrained(ocr_model_dir)
+            import torch
+            ret = VisionEncoderDecoderModel.from_pretrained(model_dir)
             assert isinstance(ret, VisionEncoderDecoderModel)
-            return ret
+            dev = torch.device('cpu')
+            if not device and torch.cuda.is_available():
+                device = 'GPU' # try
+            if device and device.startswith('GPU'):
+                try:
+                    dev = torch.device('cuda', int(device[3:] or 0))
+                    name = torch.cuda.get_device_name(dev)
+                    self.logger.info("using GPU %s (%s) for model ocr:tr", dev, name)
+                except:
+                    self.logger.exception("cannot configure GPU device")
+                    dev = torch.device('cpu')
+            if dev.type == 'cuda':
+                ret.to(dev)
             else:
-            ocr_model = load_model(ocr_model_dir, compile=False)
-            assert isinstance(ocr_model, KerasModel)
-            return KerasModel(
-                ocr_model.get_layer(name="image").input,   # type: ignore
-                ocr_model.get_layer(name="dense2").output, # type: ignore
-            )
+                self.logger.warning("no GPU device available")
+            return ret
+
+        return self.load_model('ocr', model_variant=variant, device=device)
 
     def _load_characters(self) -> List[str]:
         """
@@ -273,5 +302,6 @@ class EynollahModelZoo:
         """
         if hasattr(self, '_loaded') and getattr(self, '_loaded'):
             for needle in list(self._loaded.keys()):
+                if isinstance(self._loaded[needle], Predictor):
                     self._loaded[needle].shutdown()
                 del self._loaded[needle]