refactor(compression): migrate compress.py from model_facade to model_editor (#3580)

Replace model_facade with model_editor in compress.py and tests.
model_editor provides a cleaner API with better buffer and metadata
handling.

Update BUILD dependencies accordingly.

BUG=part of #3256

tensorflow/lite/micro/compression/BUILD

@@ -124,7 +124,7 @@ py_library(
     ],
     deps = [
         ":metadata_py",
-        ":model_facade",
+        ":model_editor",
         ":spec",
         "//tensorflow/lite/micro/tools:tflite_flatbuffer_align",
         requirement("absl_py"),
@@ -160,7 +160,7 @@ py_test(
     deps = [
         ":compress",
         ":metadata_py",
-        ":model_facade",
+        ":model_editor",
         ":spec",
         ":test_models",
         "//tensorflow/lite/python:schema_py",

tensorflow/lite/micro/compression/compress.py

@@ -29,7 +29,7 @@ import absl.flags
 import flatbuffers
 import numpy as np
 
-from tflite_micro.tensorflow.lite.micro.compression import model_facade
+from tflite_micro.tensorflow.lite.micro.compression import model_editor
 from tflite_micro.tensorflow.lite.micro.compression import spec
 from tflite_micro.tensorflow.lite.micro.compression import metadata_py_generated as schema
 from tflite_micro.tensorflow.lite.micro.tools import tflite_flatbuffer_align_wrapper
@@ -177,7 +177,7 @@ def _check_lut_compression(compression) -> spec.LookUpTableCompression:
   return compression[0]
 
 
-def _identify_compression_axis(tensor: model_facade._Tensor) -> Optional[int]:
+def _identify_compression_axis(tensor: model_editor.Tensor) -> Optional[int]:
   """Determines the axis along which to compress.
 
   The axis along which to compress is inferred from the tensor's quantization
@@ -191,16 +191,18 @@ def _identify_compression_axis(tensor: model_facade._Tensor) -> Optional[int]:
     CompressionError: If the axis cannot be determined.
   """
   q = tensor.quantization
-  if q is not None \
-      and q.scale is not None \
-      and q.quantizedDimension < len(tensor.shape):
-    quantization_channels = len(q.scale)
+  if q is not None:
+    # model_editor wraps quantization, access scales/axis from wrapper
+    scales = q.scales if isinstance(q.scales, list) else [q.scales]
+    quantization_channels = len(scales)
+
     if quantization_channels == 1:
       # Use one value table for the entire tensor
       return None
 
-    if quantization_channels == tensor.shape[q.quantizedDimension]:
-      return q.quantizedDimension
+    if q.axis is not None and q.axis < len(tensor.shape):
+      if quantization_channels == tensor.shape[q.axis]:
+        return q.axis
 
   raise CompressionError(
       f"Invalid or no quanitzation parameters from which to "
@@ -300,7 +302,7 @@ def compress(model_in: ByteString, specs: Iterable[spec.Tensor]) -> bytearray:
   Returns:
     A compressed flatbuffer.
   """
-  model = model_facade.read(model_in)
+  model = model_editor.read(model_in)
   metadata = _MetadataBuilder()
 
   for spec in specs:
@@ -316,12 +318,14 @@ def compress(model_in: ByteString, specs: Iterable[spec.Tensor]) -> bytearray:
       tensor.buffer.data = _pack_indices(compressed.indices, spec_bitwidth)
 
       # write value buffer
-      value_buffer = model.add_buffer()
-      value_buffer.data = _pack_lookup_tables(compressed.lookup_tables,
+      value_buffer_data = _pack_lookup_tables(compressed.lookup_tables,
                                               2**spec_bitwidth)
+      value_buffer = model_editor.Buffer(data=value_buffer_data)
+      model.buffers.append(value_buffer)  # Auto-sets value_buffer.index
+
       # add compression metadata for tensor
-      lut_tensor = metadata.add_lut_tensor(subgraph_id=tensor.subgraph.index)
-      lut_tensor.tensor = tensor.index
+      lut_tensor = metadata.add_lut_tensor(subgraph_id=spec.subgraph)
+      lut_tensor.tensor = spec.tensor
       lut_tensor.valueBuffer = value_buffer.index
       lut_tensor.indexBitwidth = spec_bitwidth
 
@@ -329,10 +333,10 @@ def compress(model_in: ByteString, specs: Iterable[spec.Tensor]) -> bytearray:
       raise CompressionError(f"error compressing {spec}") from e
 
   # add compression metadata to model
-  model.add_metadata(TFLITE_METADATA_KEY, metadata.compile())
+  model.metadata[TFLITE_METADATA_KEY] = metadata.compile()
 
-  # Compile the model and apply proper alignment
-  unaligned_model = model.compile()
+  # Build the model and apply proper alignment
+  unaligned_model = model.build()
   return _apply_flatbuffer_alignment(unaligned_model)
 
 

tensorflow/lite/micro/compression/compress_test.py

@@ -19,7 +19,7 @@ import unittest
 
 from tflite_micro.tensorflow.lite.micro.compression import compress
 from tflite_micro.tensorflow.lite.micro.compression import metadata_py_generated as schema
-from tflite_micro.tensorflow.lite.micro.compression import model_facade
+from tflite_micro.tensorflow.lite.micro.compression import model_editor
 from tflite_micro.tensorflow.lite.micro.compression import spec
 from tflite_micro.tensorflow.lite.micro.compression import test_models
 from tflite_micro.tensorflow.lite.python import schema_py_generated as tflite
@@ -368,12 +368,12 @@ class TestsCompression(unittest.TestCase):
   def setUpClass(cls):
     super().setUpClass()
     cls.flatbuffer = test_models.build(TEST_MODEL)
-    cls.uncompressed = model_facade.read(cls.flatbuffer)
+    cls.uncompressed = model_editor.read(cls.flatbuffer)
 
   def test_compression_metadata(self):
     """The compressed model has compression metadata."""
     compressed = compress.compress(self.flatbuffer, TEST_COMPRESSION_SPEC)
-    model = model_facade.read(compressed)
+    model = model_editor.read(compressed)
     self.assertIn("metadata0", self.uncompressed.metadata)
     self.assertIn(compress.TFLITE_METADATA_KEY, model.metadata)
 
@@ -461,16 +461,17 @@ class TestCompressedModel(unittest.TestCase):
     super().setUpClass()
     # Create a model
     uncompressed_fb = test_models.build(TEST_MODEL)
-    cls.uncompressed = model_facade.read(uncompressed_fb)
+    cls.uncompressed = model_editor.read(uncompressed_fb)
 
     # Compress the model
     compressed_fb = compress.compress(uncompressed_fb, TEST_COMPRESSION_SPEC)
-    cls.compressed = model_facade.read(compressed_fb)
+    cls.compressed = model_editor.read(compressed_fb)
 
     # Extract the compression metadata
-    metadata_flatbuffer = cls.compressed.metadata[compress.TFLITE_METADATA_KEY]
-    cls.metadata = schema.MetadataT.InitFromPackedBuf(metadata_flatbuffer.data,
-                                                      0)
+    metadata_flatbuffer_bytes = cls.compressed.metadata[
+        compress.TFLITE_METADATA_KEY]
+    cls.metadata = schema.MetadataT.InitFromPackedBuf(
+        metadata_flatbuffer_bytes, 0)
 
   def test_uncompressed_tensors(self):
     """Tensors not in compression spec are not compressed.
@@ -515,7 +516,7 @@ class TestCompressedModel(unittest.TestCase):
     indices = indices[:n_indices * bitwidth]  # trim possible padding
 
     value_buffer = self.compressed.buffers[lut_tensor.valueBuffer]
-    values = np.frombuffer(value_buffer.data, dtype=tensor_obj.dtype)
+    values = np.frombuffer(value_buffer.data, dtype=tensor_obj.numpy_dtype)
 
     return bitwidth, indices, values