IVGCVSW-4517 Implement BFloat16 Encoder and Decoder

 * Add ConvertFloat32ToBFloat16
 * Add ConvertBFloat16ToFloat32
 * Add BFloat16Encoder
 * Add BFloat16Decoder
 * Unit tests

Signed-off-by: Narumol Prangnawarat <narumol.prangnawarat@arm.com>
Change-Id: I198888384c923aba28cfbed09a02edc6f8194b3e

7 files changed, 155 insertions, 1 deletions

diff --git a/include/armnnUtils/FloatingPointConverter.hpp b/include/armnnUtils/FloatingPointConverter.hpp
index cf573a2ee8..a2244735dc 100644
--- a/include/armnnUtils/FloatingPointConverter.hpp
+++ b/include/armnnUtils/FloatingPointConverter.hpp
@@ -18,6 +18,12 @@ public:
     static void ConvertFloat32To16(const float *srcFloat32Buffer, size_t numElements, void *dstFloat16Buffer);
 
     static void ConvertFloat16To32(const void *srcFloat16Buffer, size_t numElements, float *dstFloat32Buffer);
+
+    // Converts a buffer of FP32 values to BFloat16, and stores in the given dstBFloat16Buffer.
+    static void ConvertFloat32ToBFloat16(const float* srcFloat32Buffer, size_t numElements, void* dstBFloat16Buffer);
+
+    // Converts a buffer of BFloat16 to FP32 value, and stores in the given dstFloat32Buffer.
+    static void ConvertBFloat16ToFloat32(const void* srcBFloat16Buffer, size_t numElements, float* dstFloat32Buffer);
 };
 
 } // namespace armnnUtils
diff --git a/src/armnn/test/FloatingPointConverterTest.cpp b/src/armnn/test/FloatingPointConverterTest.cpp
index 4497ca70a8..4a9e216e70 100644
--- a/src/armnn/test/FloatingPointConverterTest.cpp
+++ b/src/armnn/test/FloatingPointConverterTest.cpp
@@ -5,6 +5,7 @@
 
 #include <armnnUtils/FloatingPointConverter.hpp>
 
+#include <BFloat16.hpp>
 #include <Half.hpp>
 
 #include <boost/test/unit_test.hpp>
@@ -52,4 +53,73 @@ BOOST_AUTO_TEST_CASE(TestConvertFp16ToFp32)
     }
 }
 
+BOOST_AUTO_TEST_CASE(TestConvertFloat32ToBFloat16)
+{
+    float floatArray[] = { 1.704735E38f,   // 0x7F004000 round down
+                           0.0f,           // 0x00000000 round down
+                           2.2959E-41f,    // 0x00004000 round down
+                           1.7180272E38f,  // 0x7F014000 round down
+                           9.18355E-41f,   // 0x00010000 round down
+                           1.14794E-40f,   // 0x00014000 round down
+                           4.5918E-41f,    // 0x00008000 round down
+                           -1.708058E38f,  // 0xFF008000 round down
+                           -4.3033756E37f, // 0xFE018000 round up
+                           1.60712E-40f,   // 0x0001C000 round up
+                           -2.0234377f,    // 0xC0018001 round up
+                           -1.1800863E-38f,// 0x80808001 round up
+                           4.843037E-35f,  // 0x0680C000 round up
+                           3.9999998f,     // 0x407FFFFF round up
+                           3.4028235E38f,  // 0x7F7FFFFF max positive value
+                           -3.4028235E38f, // 0xFF7FFFFF max negative value
+                           1.1754942E-38f, // 0x007FFFFF min positive value
+                           -1.1754942E-38f // 0x807FFFFF min negative value
+                          };
+    uint16_t expectedResult[] = { 0x7F00,
+                                  0x0000,
+                                  0x0000,
+                                  0x7F01,
+                                  0x0001,
+                                  0x0001,
+                                  0x0000,
+                                  0xFF00,
+                                  0xFE02,
+                                  0x0002,
+                                  0xC002,
+                                  0x8081,
+                                  0x0681,
+                                  0x4080,
+                                  0x7F80,
+                                  0xFF80,
+                                  0x0080,
+                                  0x8080
+                                 };
+    size_t numFloats = sizeof(floatArray) / sizeof(floatArray[0]);
+
+    std::vector<armnn::BFloat16> convertedBuffer(numFloats);
+
+    armnnUtils::FloatingPointConverter::ConvertFloat32ToBFloat16(floatArray, numFloats, convertedBuffer.data());
+
+    for (size_t i = 0; i < numFloats; i++)
+    {
+        armnn::BFloat16 actual = convertedBuffer[i];
+        BOOST_CHECK_EQUAL(expectedResult[i], actual.val());
+    }
+}
+
+BOOST_AUTO_TEST_CASE(TestConvertBFloat16ToFloat32)
+{
+    uint16_t bf16Array[] = { 16256, 16320, 38699, 16384, 49156, 32639 };
+    size_t numFloats = sizeof(bf16Array) / sizeof(bf16Array[0]);
+    float expectedResult[] = { 1.0f, 1.5f, -5.525308E-25f, 2.0f, -2.0625f, 3.3895314E38f };
+    std::vector<float> convertedBuffer(numFloats, 0.0f);
+
+    armnnUtils::FloatingPointConverter::ConvertBFloat16ToFloat32(bf16Array, numFloats, convertedBuffer.data());
+
+    for (size_t i = 0; i < numFloats; i++)
+    {
+        float actual = convertedBuffer[i];
+        BOOST_CHECK_EQUAL(expectedResult[i], actual);
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/armnnUtils/BFloat16.hpp b/src/armnnUtils/BFloat16.hpp
index bb56b7d37c..965fc31c17 100644
--- a/src/armnnUtils/BFloat16.hpp
+++ b/src/armnnUtils/BFloat16.hpp
@@ -6,7 +6,7 @@
 #pragma once
 
 #include <ostream>
-#include <math.h>
+#include <cmath>
 #include <stdint.h>
 
 namespace armnn
diff --git a/src/armnnUtils/FloatingPointConverter.cpp b/src/armnnUtils/FloatingPointConverter.cpp
index 3bdde11eb8..e9b338ac7c 100644
--- a/src/armnnUtils/FloatingPointConverter.cpp
+++ b/src/armnnUtils/FloatingPointConverter.cpp
@@ -5,6 +5,7 @@
 
 #include <armnnUtils/FloatingPointConverter.hpp>
 
+#include "BFloat16.hpp"
 #include "Half.hpp"
 
 #include <boost/assert.hpp>
@@ -42,4 +43,34 @@ void FloatingPointConverter::ConvertFloat16To32(const void* srcFloat16Buffer,
     }
 }
 
+void FloatingPointConverter::ConvertFloat32ToBFloat16(const float* srcFloat32Buffer,
+                                                      size_t numElements,
+                                                      void* dstBFloat16Buffer)
+{
+    BOOST_ASSERT(srcFloat32Buffer != nullptr);
+    BOOST_ASSERT(dstBFloat16Buffer != nullptr);
+
+    armnn::BFloat16* bf16 = reinterpret_cast<armnn::BFloat16*>(dstBFloat16Buffer);
+
+    for (size_t i = 0; i < numElements; i++)
+    {
+        bf16[i] = armnn::BFloat16(srcFloat32Buffer[i]);
+    }
+}
+
+void FloatingPointConverter::ConvertBFloat16ToFloat32(const void* srcBFloat16Buffer,
+                                                      size_t numElements,
+                                                      float* dstFloat32Buffer)
+{
+    BOOST_ASSERT(srcBFloat16Buffer != nullptr);
+    BOOST_ASSERT(dstFloat32Buffer != nullptr);
+
+    const armnn::BFloat16* bf16 = reinterpret_cast<const armnn::BFloat16*>(srcBFloat16Buffer);
+
+    for (size_t i = 0; i < numElements; i++)
+    {
+        dstFloat32Buffer[i] = bf16[i].toFloat32();
+    }
+}
+
 } //namespace armnnUtils
diff --git a/src/backends/reference/workloads/BaseIterator.hpp b/src/backends/reference/workloads/BaseIterator.hpp
index c48201837b..3f0144670f 100644
--- a/src/backends/reference/workloads/BaseIterator.hpp
+++ b/src/backends/reference/workloads/BaseIterator.hpp
@@ -194,6 +194,23 @@ private:
     const int32_t m_Offset;
 };
 
+class BFloat16Decoder : public TypedIterator<const BFloat16, Decoder<float>>
+{
+public:
+    BFloat16Decoder(const BFloat16* data)
+        : TypedIterator(data) {}
+
+    BFloat16Decoder()
+        : BFloat16Decoder(nullptr) {}
+
+    float Get() const override
+    {
+        float val = 0.f;
+        armnnUtils::FloatingPointConverter::ConvertBFloat16ToFloat32(m_Iterator, 1, &val);
+        return val;
+    }
+};
+
 class Float16Decoder : public TypedIterator<const Half, Decoder<float>>
 {
 public:
@@ -355,6 +372,28 @@ private:
     const int32_t m_Offset;
 };
 
+class BFloat16Encoder : public TypedIterator<armnn::BFloat16, Encoder<float>>
+{
+public:
+    BFloat16Encoder(armnn::BFloat16* data)
+        : TypedIterator(data) {}
+
+    BFloat16Encoder()
+        : BFloat16Encoder(nullptr) {}
+
+    void Set(float right) override
+    {
+        armnnUtils::FloatingPointConverter::ConvertFloat32ToBFloat16(&right, 1, m_Iterator);
+    }
+
+    float Get() const override
+    {
+        float val = 0.f;
+        armnnUtils::FloatingPointConverter::ConvertBFloat16ToFloat32(m_Iterator, 1, &val);
+        return val;
+    }
+};
+
 class Float16Encoder : public TypedIterator<Half, Encoder<float>>
 {
 public:
diff --git a/src/backends/reference/workloads/Decoders.hpp b/src/backends/reference/workloads/Decoders.hpp
index 6a8c756048..83c57c1169 100644
--- a/src/backends/reference/workloads/Decoders.hpp
+++ b/src/backends/reference/workloads/Decoders.hpp
@@ -102,6 +102,10 @@ inline std::unique_ptr<Decoder<float>> MakeDecoder(const TensorInfo& info, const
                 info.GetQuantizationScale(),
                 info.GetQuantizationOffset());
         }
+        case DataType::BFloat16:
+        {
+            return std::make_unique<BFloat16Decoder>(static_cast<const BFloat16*>(data));
+        }
         case DataType::Float16:
         {
             return std::make_unique<Float16Decoder>(static_cast<const Half*>(data));
diff --git a/src/backends/reference/workloads/Encoders.hpp b/src/backends/reference/workloads/Encoders.hpp
index f52297602f..e93987da31 100644
--- a/src/backends/reference/workloads/Encoders.hpp
+++ b/src/backends/reference/workloads/Encoders.hpp
@@ -75,6 +75,10 @@ inline std::unique_ptr<Encoder<float>> MakeEncoder(const TensorInfo& info, void*
         {
             return std::make_unique<Int32Encoder>(static_cast<int32_t*>(data));
         }
+        case armnn::DataType::BFloat16:
+        {
+            return std::make_unique<BFloat16Encoder>(static_cast<armnn::BFloat16*>(data));
+        }
         case armnn::DataType::Float16:
         {
             return std::make_unique<Float16Encoder>(static_cast<Half*>(data));