IVGCVSW-2858 Add support for QSymm16 quantization

Change-Id: Ia7c305c30c39ec0e9db447a461479be17fde250c
Signed-off-by: Nattapat Chaimanowong <nattapat.chaimanowong@arm.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/src/armnn/NetworkQuantizationScheme.hpp b/src/armnn/NetworkQuantizationScheme.hpp
new file mode 100644
index 0000000000..065205dada
--- /dev/null
+++ b/src/armnn/NetworkQuantizationScheme.hpp
@@ -0,0 +1,80 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#pragma once
+
+#include <armnn/Types.hpp>
+
+#include <cmath>
+#include <algorithm>
+
+namespace armnn
+{
+
+using OffsetScalePair = std::pair<float, int>;
+
+struct IQuantizationScheme
+{
+    virtual OffsetScalePair ComputeScheme(double min, double max) const = 0;
+
+    virtual int NumBits() const = 0;
+
+    virtual DataType GetDataType() const = 0;
+
+    virtual ~IQuantizationScheme() {}
+};
+
+struct QAsymm8QuantizationScheme : IQuantizationScheme
+{
+    OffsetScalePair ComputeScheme(double min, double max) const override
+    {
+        if (min >= max)
+        {
+            throw InvalidArgumentException("min >= max will result in invalid quantization.");
+        }
+
+        double highest = (1 << NumBits()) - 1;
+
+        min = std::min(0.0, min); // min <= 0.0
+        max = std::max(0.0, max); // max >= 0.0
+
+        // Assumes quantization range [0-highest]
+        double scale = (max-min) / highest;
+        double offset = -min / scale;
+
+        // Clamp offset [0-highest]
+        offset = std::max(0.0, std::min(highest, offset));
+
+        return std::make_pair(static_cast<float>(scale), static_cast<int>(std::round(offset)));
+    }
+
+    int NumBits() const override { return 8; }
+
+    DataType GetDataType() const override { return DataType::QuantisedAsymm8; }
+};
+
+struct QSymm16QuantizationScheme : IQuantizationScheme
+{
+    OffsetScalePair ComputeScheme(double min, double max) const override
+    {
+        if (min >= max)
+        {
+            throw InvalidArgumentException("min >= max will result in invalid quantization.");
+        }
+
+        double highest = (1 << (NumBits()-1)) - 1; // (numbits-1) accounts for the sign bit
+
+        double extent = std::max(std::abs(min), std::abs(max));
+        double scale = extent / highest;
+
+        return std::make_pair(static_cast<float>(scale), 0);
+    }
+
+    int NumBits() const override { return 16; }
+
+    DataType GetDataType() const override { return DataType::QuantisedSymm16; }
+};
+
+} // namespace armnn