Propagate half precision float through tflite

PiperOrigin-RevId: 247082214

tensorflow/lite/BUILD

@@ -252,6 +252,7 @@ cc_test(
         "//tensorflow/lite/kernels/internal:tensor_utils",
         "//tensorflow/lite/schema:schema_fbs",
         "//tensorflow/lite/testing:util",
+        "//third_party/eigen3",
         "@com_google_googletest//:gtest",
     ],
 )

tensorflow/lite/c/c_api_internal.c

@@ -172,6 +172,8 @@ const char* TfLiteTypeGetName(TfLiteType type) {
       return "COMPLEX64";
     case kTfLiteString:
       return "STRING";
+    case kTfLiteFloat16:
+      return "FLOAT16";
   }
   return "Unknown type";
 }

tensorflow/lite/c/c_api_internal.h

@@ -195,6 +195,11 @@ typedef struct {
   float re, im;  // real and imaginary parts, respectively.
 } TfLiteComplex64;
 
+// Half precision data type compatible with the C99 definition.
+typedef struct {
+  uint16_t data;
+} TfLiteFloat16;
+
 // Types supported by tensor
 typedef enum {
   kTfLiteNoType = 0,
@@ -207,6 +212,7 @@ typedef enum {
   kTfLiteInt16 = 7,
   kTfLiteComplex64 = 8,
   kTfLiteInt8 = 9,
+  kTfLiteFloat16 = 10,
 } TfLiteType;
 
 // Return the name of a given type, for error reporting purposes.
@@ -259,6 +265,8 @@ typedef union {
   int32_t* i32;
   int64_t* i64;
   float* f;
+  // Placeholder for 16b float type. Use uint16* in the pointer union for now.
+  TfLiteFloat16* f16;
   char* raw;
   const char* raw_const;
   uint8_t* uint8;

tensorflow/lite/c/c_api_internal_test.cc

@@ -78,6 +78,7 @@ TEST(Types, TestTypeNames) {
   };
   EXPECT_EQ(type_name(kTfLiteNoType), "NOTYPE");
   EXPECT_EQ(type_name(kTfLiteFloat32), "FLOAT32");
+  EXPECT_EQ(type_name(kTfLiteFloat16), "FLOAT16");
   EXPECT_EQ(type_name(kTfLiteInt16), "INT16");
   EXPECT_EQ(type_name(kTfLiteInt32), "INT32");
   EXPECT_EQ(type_name(kTfLiteUInt8), "UINT8");

tensorflow/lite/core/api/flatbuffer_conversions.cc

@@ -61,9 +61,8 @@ TfLiteStatus ConvertTensorType(TensorType tensor_type, TfLiteType* type,
       *type = kTfLiteFloat32;
       break;
     case TensorType_FLOAT16:
-      error_reporter->Report("Unimplemented data type float16 in tensor\n",
+      *type = kTfLiteFloat16;
-                             tensor_type);
+      break;
-      return kTfLiteError;
     case TensorType_INT16:
       *type = kTfLiteInt16;
       break;

tensorflow/lite/core/api/flatbuffer_conversions_test.cc

@@ -141,6 +141,13 @@ TEST_F(FlatbufferConversionsTest, TestConvertTensorType) {
   EXPECT_EQ(kTfLiteFloat32, type);
 }
 
+TEST_F(FlatbufferConversionsTest, TestConvertTensorTypeFloat16) {
+  TfLiteType type;
+  EXPECT_EQ(kTfLiteOk,
+            ConvertTensorType(TensorType_FLOAT16, &type, &mock_reporter_));
+  EXPECT_EQ(kTfLiteFloat16, type);
+}
+
 }  // namespace tflite
 
 int main(int argc, char** argv) {

tensorflow/lite/core/subgraph.cc

@@ -469,6 +469,9 @@ TfLiteStatus Subgraph::BytesRequired(TfLiteType type, const int* dims,
     case kTfLiteInt8:
       *bytes = sizeof(int8_t) * count;
       break;
+    case kTfLiteFloat16:
+      *bytes = sizeof(TfLiteFloat16) * count;
+      break;
     default:
       ReportError(
           "Only float32, int8, int16, int32, int64, uint8, bool, complex64 "

tensorflow/lite/delegates/flex/util.cc

@@ -60,6 +60,8 @@ TF_DataType GetTensorFlowDataType(TfLiteType type) {
       return TF_FLOAT;
     case kTfLiteFloat32:
       return TF_FLOAT;
+    case kTfLiteFloat16:
+      return TF_HALF;
     case kTfLiteInt16:
       return TF_INT16;
     case kTfLiteInt32:
@@ -83,6 +85,8 @@ TfLiteType GetTensorFlowLiteType(TF_DataType type) {
   switch (type) {
     case TF_FLOAT:
       return kTfLiteFloat32;
+    case TF_HALF:
+      return kTfLiteFloat16;
     case TF_INT16:
       return kTfLiteInt16;
     case TF_INT32:

tensorflow/lite/delegates/flex/util_test.cc

@@ -101,9 +101,9 @@ TEST(UtilTest, CopyShapeAndType) {
 
   EXPECT_EQ(
       CopyShapeAndType(&context, Tensor(tensorflow::DT_HALF, {1, 2}), &dst),
-      kTfLiteError);
+      kTfLiteOk);
-  EXPECT_EQ(context.error,
+  EXPECT_THAT(context.new_size, ElementsAre(1, 2));
-            "TF Lite does not support TensorFlow data type: half");
+  EXPECT_EQ(dst.type, kTfLiteFloat16);
 }
 
 TEST(UtilTest, TypeConversionsFromTFLite) {

tensorflow/lite/experimental/objc/apis/TFLTensor.h

@@ -29,6 +29,9 @@ typedef NS_ENUM(NSUInteger, TFLTensorDataType) {
   /** 32-bit single precision floating point. */
   TFLTensorDataTypeFloat32,
 
+  /** 16-bit half precision floating point. */
+  TFLTensorDataTypeFloat16,
+
   /** 32-bit signed integer. */
   TFLTensorDataTypeInt32,
 

tensorflow/lite/experimental/objc/sources/TFLInterpreter.mm

@@ -366,6 +366,8 @@ static void TFLInterpreterErrorReporter(void *user_data, const char *format, va_
   switch (cTensorType) {
     case kTfLiteFloat32:
       return TFLTensorDataTypeFloat32;
+    case kTfLiteFloat16:
+      return TFLTensorDataTypeFloat16;
     case kTfLiteInt32:
       return TFLTensorDataTypeInt32;
     case kTfLiteUInt8:

tensorflow/lite/experimental/writer/enum_mapping.h

@@ -62,6 +62,8 @@ inline TensorType TfLiteTypeToSchemaType(TfLiteType type) {
       return TensorType_FLOAT32;  // TODO(aselle): Consider an error.
     case kTfLiteFloat32:
       return TensorType_FLOAT32;
+    case kTfLiteFloat16:
+      return TensorType_FLOAT16;
     case kTfLiteInt32:
       return TensorType_INT32;
     case kTfLiteUInt8:

tensorflow/lite/interpreter.cc

@@ -30,6 +30,11 @@ limitations under the License.
 #include "tensorflow/lite/schema/schema_generated.h"
 #include "tensorflow/lite/util.h"
 
+// TODO(b/132087118): move static_assert to c_api_internal when compiled with
+// C++.
+static_assert(sizeof(TfLiteFloat16) == sizeof(uint16_t),
+              "Float 16 type must be 16 bits.");
+
 namespace tflite {
 
 namespace {

tensorflow/lite/interpreter.h

@@ -74,6 +74,10 @@ constexpr TfLiteType typeToTfLiteType<string>() {
   return kTfLiteString;
 }
 
+template <>
+constexpr TfLiteType typeToTfLiteType<TfLiteFloat16>() {
+  return kTfLiteFloat16;
+}
 // An interpreter for a graph of nodes that input and output from tensors.
 // Each node of the graph processes a set of input tensors and produces a
 // set of output Tensors. All inputs/output tensors are referenced by index.

tensorflow/lite/interpreter_test.cc

@@ -17,6 +17,7 @@ limitations under the License.
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
+#include "third_party/eigen3/Eigen/Core"
 #include "tensorflow/lite/core/api/error_reporter.h"
 #include "tensorflow/lite/kernels/internal/compatibility.h"
 #include "tensorflow/lite/kernels/kernel_util.h"
@@ -165,7 +166,7 @@ TEST(BasicInterpreter, CheckAllocate) {
   } cases[] = {
       {kTfLiteFloat32, sizeof(float)}, {kTfLiteInt32, sizeof(int32_t)},
       {kTfLiteUInt8, sizeof(uint8_t)}, {kTfLiteInt64, sizeof(int64_t)},
-      {kTfLiteInt16, sizeof(int16_t)},
+      {kTfLiteInt16, sizeof(int16_t)}, {kTfLiteFloat16, sizeof(TfLiteFloat16)},
   };
 
   for (auto test : cases) {
@@ -238,6 +239,8 @@ TEST(BasicInterpreter, CheckResize) {
   const uint8_t uint8s[] = {3, 4};
   const int64_t int64s[] = {6, -7};
   const int16_t int16s[] = {8, -9};
+  const Eigen::half float16s[] = {Eigen::half_impl::float_to_half_rtne(-3.f),
+                                  Eigen::half_impl::float_to_half_rtne(-4.f)};
 
   struct {
     TfLiteType type;
@@ -249,6 +252,8 @@ TEST(BasicInterpreter, CheckResize) {
       {kTfLiteUInt8, sizeof(uint8_t), reinterpret_cast<const char*>(uint8s)},
       {kTfLiteInt64, sizeof(int64_t), reinterpret_cast<const char*>(int64s)},
       {kTfLiteInt16, sizeof(int16_t), reinterpret_cast<const char*>(int16s)},
+      {kTfLiteFloat16, sizeof(TfLiteFloat16),
+       reinterpret_cast<const char*>(float16s)},
   };
 
   for (auto test : cases) {
@@ -283,10 +288,8 @@ TEST(BasicInterpreter, CheckResize) {
 TEST(BasicInterpreter, CheckAlignment) {
   struct {
     TfLiteType type;
-  } cases[] = {
+  } cases[] = {{kTfLiteFloat32}, {kTfLiteInt32}, {kTfLiteUInt8},
-      {kTfLiteFloat32}, {kTfLiteInt32}, {kTfLiteUInt8},
+               {kTfLiteInt64},   {kTfLiteInt16}, {kTfLiteFloat16}};
-      {kTfLiteInt64},   {kTfLiteInt16},
-  };
 
   for (auto test : cases) {
     Interpreter interpreter;

tensorflow/lite/kernels/internal/tensor_ctypes.h

@@ -66,6 +66,11 @@ inline const float* GetTensorData(const TfLiteTensor* tensor) {
   return tensor != nullptr ? tensor->data.f : nullptr;
 }
 
+template <>
+inline const TfLiteFloat16* GetTensorData(const TfLiteTensor* tensor) {
+  return tensor != nullptr ? tensor->data.f16 : nullptr;
+}
+
 template <>
 inline const uint8_t* GetTensorData(const TfLiteTensor* tensor) {
   return tensor != nullptr ? tensor->data.uint8 : nullptr;

tensorflow/lite/kernels/test_util.h

@@ -20,7 +20,6 @@ limitations under the License.
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
-
 #include "tensorflow/core/platform/logging.h"
 #include "tensorflow/lite/interpreter.h"
 #include "tensorflow/lite/kernels/internal/tensor_utils.h"
@@ -568,6 +567,7 @@ class SingleOpTest : public ::testing::TestWithParam<string> {
 template <typename T>
 TensorType GetTensorType() {
   if (std::is_same<T, float>::value) return TensorType_FLOAT32;
+  if (std::is_same<T, TfLiteFloat16>::value) return TensorType_FLOAT16;
   if (std::is_same<T, int32_t>::value) return TensorType_INT32;
   if (std::is_same<T, uint8_t>::value) return TensorType_UINT8;
   if (std::is_same<T, string>::value) return TensorType_STRING;

tensorflow/lite/optional_debug_tools.cc

@@ -56,6 +56,8 @@ const char* TensorTypeName(TfLiteType type) {
       return "kTfLiteInt16";
     case kTfLiteComplex64:
       return "kTfLiteComplex64";
+    case kTfLiteFloat16:
+      return "kTfLiteFloat16";
   }
   return "(invalid)";
 }

tensorflow/lite/python/interpreter_wrapper/python_utils.cc

@@ -32,6 +32,8 @@ int TfLiteTypeToPyArrayType(TfLiteType tf_lite_type) {
   switch (tf_lite_type) {
     case kTfLiteFloat32:
       return NPY_FLOAT32;
+    case kTfLiteFloat16:
+      return NPY_FLOAT16;
     case kTfLiteInt32:
       return NPY_INT32;
     case kTfLiteInt16:

tensorflow/lite/python/optimize/calibration_wrapper.cc

@@ -61,6 +61,8 @@ inline TensorType TfLiteTypeToSchemaType(TfLiteType type) {
       return TensorType_FLOAT32;  // TODO(b/129336260): No schema type for none.
     case kTfLiteFloat32:
       return TensorType_FLOAT32;
+    case kTfLiteFloat16:
+      return TensorType_FLOAT16;
     case kTfLiteInt32:
       return TensorType_INT32;
     case kTfLiteUInt8:

tensorflow/lite/python/util.py

@@ -31,6 +31,7 @@ from tensorflow.python.training.saver import export_meta_graph as _export_meta_g
 # Map of tf.dtypes to TFLite types_flag_pb2.
 _MAP_TF_TO_TFLITE_TYPES = {
     dtypes.float32: _types_pb2.FLOAT,
+    dtypes.float16: _types_pb2.FLOAT16,
     dtypes.int32: _types_pb2.INT32,
     dtypes.int64: _types_pb2.INT64,
     dtypes.string: _types_pb2.STRING,

tensorflow/lite/python/util_test.py

@@ -50,6 +50,8 @@ class UtilTest(test_util.TensorFlowTestCase):
     self.assertEqual(
         util.convert_dtype_to_tflite_type(dtypes.complex64),
         _types_pb2.COMPLEX64)
+    self.assertEqual(
+        util.convert_dtype_to_tflite_type(dtypes.half), _types_pb2.FLOAT16)
     with self.assertRaises(ValueError):
       util.convert_dtype_to_tflite_type(dtypes.bool)
 

tensorflow/lite/toco/model.h

@@ -223,6 +223,7 @@ enum class ArrayDataType : uint8 {
   kUint64,  // 10
   kString,
   kComplex64,
+  kFloat16,
 };
 
 // Compile-time logic to map ArrayDataType to the corresponding C++ scalar type

tensorflow/lite/toco/types.proto

@@ -46,4 +46,7 @@ enum IODataType {
 
   // Int8, quantized based on QuantizationParameters in schema.
   INT8 = 9;
+
+  // Half precision float, not quantized.
+  FLOAT16 = 10;
 }