IVGCVSW-4520 Implement BFloat16 Optimizer

 * Add ReduceFp32ToBf16 to OptimizerOptions
 * Add ConvertFp32NetworkToBf16
 * Add utility functions to insert conversion layers
 * Add constant conversion BF16 <-> FP32
 * Unit tests

Signed-off-by: Narumol Prangnawarat <narumol.prangnawarat@arm.com>
Change-Id: Iaff77e20c721400b052cb37eb9ef6fe16d7abaff

1 files changed, 81 insertions, 0 deletions

diff --git a/src/armnn/optimizations/ConvertFp32NetworkToBf16.hpp b/src/armnn/optimizations/ConvertFp32NetworkToBf16.hpp
new file mode 100644
index 0000000000..d6350c3af3
--- /dev/null
+++ b/src/armnn/optimizations/ConvertFp32NetworkToBf16.hpp
@@ -0,0 +1,81 @@
+//
+// Copyright © 2020 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include "Optimization.hpp"
+#include "NetworkUtils.hpp"
+
+namespace armnn
+{
+namespace optimizations
+{
+
+class ConvertFp32NetworkToBf16Impl
+{
+public:
+    void Run(Graph& graph, Layer& layer) const
+    {
+        if(layer.GetType() == LayerType::Input)
+        {
+            // if the outputs of this layer are DataType::Float32
+            // add a ConvertFloat32ToBFloat16 layer after each of the outputs
+            if (layer.GetDataType() == DataType::Float32)
+            {
+                InsertConvertFp32ToBf16LayersAfter(graph, layer);
+            }
+        }
+        else if (layer.GetType() == LayerType::Output)
+        {
+            // if the inputs of this layer are DataType::Float32
+            // add a ConvertBFloat16ToFloat32 layer before each of the inputs
+            if (layer.GetDataType() == DataType::Float32)
+            {
+                // NOTE: We need to call InsertConvertBf16ToFp32LayersBefore with expectCorrectInputType = false
+                // here, otherwise it will expect the inputs to be DataType::BFloat16
+                InsertConvertBf16ToFp32LayersBefore(graph, layer, false);
+            }
+        }
+        else if (layer.GetType() != LayerType::ConvertFp32ToBf16 && layer.GetType() != LayerType::ConvertBf16ToFp32)
+        {
+            // if the inputs/outputs of this layer are DataType::Float32
+            // change the data type for all inputs and outputs to DataType::BFloat16
+            for (auto&& input = layer.BeginInputSlots(); input != layer.EndInputSlots(); ++input)
+            {
+                // if it is connected to OutputSlot of the InputLayer do not change the DataType of connection
+                // InputSlots of the current layer will be updated when conversion layer is inserted after InputLayer
+                Layer& base = input->GetConnectedOutputSlot()->GetOwningLayer();
+                if (base.GetType() != LayerType::Input)
+                {
+                    TensorInfo convertInfo = input->GetConnection()->GetTensorInfo();
+                    if (convertInfo.GetDataType() == DataType::Float32)
+                    {
+                        convertInfo.SetDataType(DataType::BFloat16);
+                        input->GetConnection()->SetTensorInfo(convertInfo);
+                    }
+                }
+            }
+
+            // change outputs to DataType::BFloat16
+            for (auto&& output = layer.BeginOutputSlots(); output != layer.EndOutputSlots(); ++output)
+            {
+                TensorInfo convertInfo = output->GetTensorInfo();
+                if (convertInfo.GetDataType() == DataType::Float32)
+                {
+                    convertInfo.SetDataType(DataType::BFloat16);
+                    output->SetTensorInfo(convertInfo);
+                }
+            }
+        }
+    }
+
+protected:
+    ConvertFp32NetworkToBf16Impl() = default;
+    ~ConvertFp32NetworkToBf16Impl() = default;
+};
+
+using Fp32NetworkToBf16Converter = OptimizeForType<Layer, ConvertFp32NetworkToBf16Impl>;
+
+} // namespace optimizations
+} // namespace armnn