Enable flex delegate on tensorflow.lite.Interpreter Python package

Usually, flex delegate is enabled by symbol override of AcquireFlexDelegate()
function. But this approach doesn't work well with shared library.

Since pywrap_tensorflow_internal.so is available for tensorflow PIP,
I've made the following changes to enable flex delegate.
- Included flex delegate module to the pywrap_tensorflow_internal.so.
  This file already contains most TF internal logic and having TFLite flex
  delegate impacts about 72K to the output.
- Added new function of TF_AcquireFlexDelegate() in the delegate module.
- Updated logic in AcquireFlexDelegate() of interpreter_builder.cc to check
  the availability of pywrap_tensorflow_internal.so and lookup the
  TF_AcquireFlexDelegate() symbol to enable flex delegate.

Also updated python/lite_flex_test.py since flex delegate is supported with
Python API

PiperOrigin-RevId: 317044994
Change-Id: Ic5e953f4a675b3f5360a4c7d607568193103711a

tensorflow/lite/delegates/flex/delegate.cc

@@ -136,3 +136,10 @@ TfLiteStatus FlexDelegate::CopyFromBufferHandle(
 }
 
 }  // namespace tflite
+
+// Exported C interface function which is used by AcquireFlexDelegate() at
+// interpreter_build.cc. To export the function name globally, the function name
+// must be matched with patterns in tf_version_script.lds
+extern "C" tflite::TfLiteDelegateUniquePtr TF_AcquireFlexDelegate() {
+  return tflite::AcquireFlexDelegate();
+}

tensorflow/lite/interpreter_builder.cc

@@ -14,6 +14,9 @@ limitations under the License.
 ==============================================================================*/
 #include "tensorflow/lite/interpreter_builder.h"
 
+#if !defined(__ANDROID__) && !defined(__APPLE__) && !defined(_WIN32)
+#include <dlfcn.h>
+#endif
 #include <fcntl.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -114,6 +117,20 @@ const char* kEmptyTensorName = "";
 // For flex delegate, see also the strong override in
 // lite/delegates/flex/delegate.cc.
 TFLITE_ATTRIBUTE_WEAK Interpreter::TfLiteDelegatePtr AcquireFlexDelegate() {
+#if !defined(__ANDROID__) && !defined(__APPLE__) && !defined(_WIN32)
+  // If _pywrap_tensorflow_internal.so is available, use
+  // TF_AcquireFlexDelegate() to initialize flex delegate.
+  void* lib_tf_internal =
+      dlopen("_pywrap_tensorflow_internal.so", RTLD_NOW | RTLD_LOCAL);
+  if (lib_tf_internal) {
+    auto TF_AcquireFlexDelegate =
+        reinterpret_cast<Interpreter::TfLiteDelegatePtr (*)()>(
+            dlsym(lib_tf_internal, "TF_AcquireFlexDelegate"));
+    if (TF_AcquireFlexDelegate) {
+      return TF_AcquireFlexDelegate();
+    }
+  }
+#endif
   return Interpreter::TfLiteDelegatePtr(nullptr, [](TfLiteDelegate*) {});
 }
 

tensorflow/lite/python/BUILD

@@ -193,9 +193,8 @@ py_test(
     python_version = "PY3",
     srcs_version = "PY2AND3",
     tags = [
-        # TODO(b/111881877): Enable in oss after resolving op registry issues.
+        "no_mac",  # TODO(b/159077703): Enable Python API Flex support on MacOS.
-        "no_oss",
+        "no_windows",  # TODO(b/159077703): Enable Python API Flex support on Windows.
-        "no_windows",
     ],
     deps = [
         ":lite",

tensorflow/lite/python/lite_flex_test.py

@@ -19,6 +19,7 @@ from __future__ import division
 from __future__ import print_function
 
 from absl.testing import parameterized
+import numpy as np
 
 from tensorflow.lite.python import lite
 from tensorflow.lite.python.interpreter import Interpreter
@@ -41,8 +42,7 @@ class FromSessionTest(test_util.TensorFlowTestCase, parameterized.TestCase):
       ('DisableMlirConverter', False))  # disable mlir
   def testFlexMode(self, enable_mlir):
     with ops.Graph().as_default():
-      in_tensor = array_ops.placeholder(
+      in_tensor = array_ops.placeholder(shape=[1, 4], dtype=dtypes.float32)
-          shape=[1, 16, 16, 3], dtype=dtypes.float32)
       out_tensor = in_tensor + in_tensor
       sess = session.Session()
 
@@ -54,19 +54,22 @@ class FromSessionTest(test_util.TensorFlowTestCase, parameterized.TestCase):
     tflite_model = converter.convert()
     self.assertTrue(tflite_model)
 
-    # Ensures the model contains TensorFlow ops.
+    # Check the model works with TensorFlow ops.
-    # TODO(nupurgarg): Check values once there is a Python delegate interface.
     interpreter = Interpreter(model_content=tflite_model)
-    with self.assertRaises(RuntimeError) as error:
     interpreter.allocate_tensors()
-    self.assertIn(
+    input_details = interpreter.get_input_details()
-        'Regular TensorFlow ops are not supported by this interpreter.',
+    test_input = np.array([[1.0, 2.0, 3.0, 4.0]], dtype=np.float32)
-        str(error.exception))
+    interpreter.set_tensor(input_details[0]['index'], test_input)
+    interpreter.invoke()
+
+    output_details = interpreter.get_output_details()
+    expected_output = np.array([[2.0, 4.0, 6.0, 8.0]], dtype=np.float32)
+    output_data = interpreter.get_tensor(output_details[0]['index'])
+    self.assertTrue((expected_output == output_data).all())
 
   def testDeprecatedFlags(self):
     with ops.Graph().as_default():
-      in_tensor = array_ops.placeholder(
+      in_tensor = array_ops.placeholder(shape=[1, 4], dtype=dtypes.float32)
-          shape=[1, 16, 16, 3], dtype=dtypes.float32)
       out_tensor = in_tensor + in_tensor
       sess = session.Session()
 
@@ -83,14 +86,18 @@ class FromSessionTest(test_util.TensorFlowTestCase, parameterized.TestCase):
     tflite_model = converter.convert()
     self.assertTrue(tflite_model)
 
-    # Ensures the model contains TensorFlow ops.
+    # Check the model works with TensorFlow ops.
-    # TODO(nupurgarg): Check values once there is a Python delegate interface.
     interpreter = Interpreter(model_content=tflite_model)
-    with self.assertRaises(RuntimeError) as error:
     interpreter.allocate_tensors()
-    self.assertIn(
+    input_details = interpreter.get_input_details()
-        'Regular TensorFlow ops are not supported by this interpreter.',
+    test_input = np.array([[1.0, 2.0, 3.0, 4.0]], dtype=np.float32)
-        str(error.exception))
+    interpreter.set_tensor(input_details[0]['index'], test_input)
+    interpreter.invoke()
+
+    output_details = interpreter.get_output_details()
+    expected_output = np.array([[2.0, 4.0, 6.0, 8.0]], dtype=np.float32)
+    output_data = interpreter.get_tensor(output_details[0]['index'])
+    self.assertTrue((expected_output == output_data).all())
 
 
 class FromConcreteFunctionTest(test_util.TensorFlowTestCase,
@@ -114,14 +121,18 @@ class FromConcreteFunctionTest(test_util.TensorFlowTestCase,
     converter.experimental_new_converter = enable_mlir
     tflite_model = converter.convert()
 
-    # Ensures the model contains TensorFlow ops.
+    # Check the model works with TensorFlow ops.
-    # TODO(nupurgarg): Check values once there is a Python delegate interface.
     interpreter = Interpreter(model_content=tflite_model)
-    with self.assertRaises(RuntimeError) as error:
     interpreter.allocate_tensors()
-    self.assertIn(
+    input_details = interpreter.get_input_details()
-        'Regular TensorFlow ops are not supported by this interpreter.',
+    test_input = np.array([4.0], dtype=np.float32)
-        str(error.exception))
+    interpreter.set_tensor(input_details[0]['index'], test_input)
+    interpreter.invoke()
+
+    output_details = interpreter.get_output_details()
+    expected_output = np.array([24.0], dtype=np.float32)
+    output_data = interpreter.get_tensor(output_details[0]['index'])
+    self.assertTrue((expected_output == output_data).all())
 
 
 if __name__ == '__main__':

tensorflow/python/BUILD

@@ -6058,7 +6058,12 @@ pywrap_tensorflow_macro(
         "@ngraph_tf//:ngraph_tf",
     ]) + if_xla_available([
         "//tensorflow/compiler/aot:tfcompile_lib",
-    ]),
+    ]) + select({
+        "//tensorflow:windows": [],  # TODO(b/159077703): Enable Flex on Windows
+        "//conditions:default": [
+            "//tensorflow/lite/delegates/flex:delegate",
+        ],
+    }),
 )
 
 # ** Targets for Windows build (start) **