IVGCVSW-3420 Add Serialization support for the new Stack layer

 * Adds serialization/deserialization support
 * Adds related unit test

Signed-off-by: Matthew Jackson <matthew.jackson@arm.com>
Change-Id: I69deb5397b8a06c679715e24971e9bb1c282140d

7 files changed, 143 insertions, 3 deletions

diff --git a/src/armnnDeserializer/Deserializer.cpp b/src/armnnDeserializer/Deserializer.cpp
index 461208bf39..7f1831c989 100644
--- a/src/armnnDeserializer/Deserializer.cpp
+++ b/src/armnnDeserializer/Deserializer.cpp
@@ -223,6 +223,7 @@ m_ParserFunctions(Layer_MAX+1, &Deserializer::ParseUnsupportedLayer)
     m_ParserFunctions[Layer_SpaceToBatchNdLayer]         = &Deserializer::ParseSpaceToBatchNd;
     m_ParserFunctions[Layer_SpaceToDepthLayer]           = &Deserializer::ParseSpaceToDepth;
     m_ParserFunctions[Layer_SplitterLayer]               = &Deserializer::ParseSplitter;
+    m_ParserFunctions[Layer_StackLayer]                  = &Deserializer::ParseStack;
     m_ParserFunctions[Layer_StridedSliceLayer]           = &Deserializer::ParseStridedSlice;
     m_ParserFunctions[Layer_SubtractionLayer]            = &Deserializer::ParseSubtraction;
     m_ParserFunctions[Layer_SwitchLayer]                 = &Deserializer::ParseSwitch;
@@ -315,6 +316,8 @@ Deserializer::LayerBaseRawPtr Deserializer::GetBaseLayer(const GraphPtr& graphPt
             return graphPtr->layers()->Get(layerIndex)->layer_as_SpaceToDepthLayer()->base();
         case Layer::Layer_SplitterLayer:
             return graphPtr->layers()->Get(layerIndex)->layer_as_SplitterLayer()->base();
+        case Layer::Layer_StackLayer:
+            return graphPtr->layers()->Get(layerIndex)->layer_as_StackLayer()->base();
         case Layer::Layer_StridedSliceLayer:
             return graphPtr->layers()->Get(layerIndex)->layer_as_StridedSliceLayer()->base();
         case Layer::Layer_SubtractionLayer:
@@ -2314,4 +2317,52 @@ void Deserializer::ParseTransposeConvolution2d(GraphPtr graph, unsigned int laye
     RegisterOutputSlots(graph, layerIndex, layer);
 }
 
+void Deserializer::ParseStack(GraphPtr graph, unsigned int layerIndex)
+{
+    CHECK_LAYERS(graph, 0, layerIndex);
+    auto inputs = GetInputs(graph, layerIndex);
+
+    auto outputs = GetOutputs(graph, layerIndex);
+    CHECK_VALID_SIZE(outputs.size(), 1);
+
+    auto flatBufferDescriptor = graph->layers()->Get(layerIndex)->layer_as_StackLayer()->descriptor();
+    unsigned int axis = flatBufferDescriptor->axis();
+    unsigned int numInputs = flatBufferDescriptor->numInputs();
+    CHECK_VALID_SIZE(inputs.size(), numInputs);
+
+    auto flatBufferInputShape = flatBufferDescriptor->inputShape();
+    std::vector<uint32_t> vectorInputShape(flatBufferInputShape->begin(),
+                                           flatBufferInputShape->begin() + flatBufferInputShape->size());
+
+    TensorShape inputShape(static_cast<unsigned int>(vectorInputShape.size()), vectorInputShape.data());
+    armnn::StackDescriptor descriptor(axis, numInputs, inputShape);
+
+    for (unsigned int i=0; i<inputs.size(); ++i)
+    {
+        armnn::TensorShape& inputShape = ToTensorInfo(inputs[i]).GetShape();
+        if (descriptor.m_InputShape != inputShape)
+        {
+            std::stringstream ss;
+            ss << "Shape of input  "
+               << i
+               << " "
+               << inputShape
+               << " does not equal defined input shape "
+               << descriptor.m_InputShape
+               << ": "
+               << CHECK_LOCATION().AsString();
+            throw ParseException(ss.str());
+        }
+    }
+
+    auto layerName = GetLayerName(graph, layerIndex);
+    IConnectableLayer* layer = m_Network->AddStackLayer(descriptor, layerName.c_str());
+
+    armnn::TensorInfo outputTensorInfo = ToTensorInfo(outputs[0]);
+    layer->GetOutputSlot(0).SetTensorInfo(outputTensorInfo);
+
+    RegisterInputSlots(graph, layerIndex, layer);
+    RegisterOutputSlots(graph, layerIndex, layer);
+}
+
 } // namespace armnnDeserializer
diff --git a/src/armnnDeserializer/Deserializer.hpp b/src/armnnDeserializer/Deserializer.hpp
index 6a63f0fb6a..b9d6a170a1 100644
--- a/src/armnnDeserializer/Deserializer.hpp
+++ b/src/armnnDeserializer/Deserializer.hpp
@@ -113,6 +113,7 @@ private:
     void ParseSpaceToBatchNd(GraphPtr graph, unsigned int layerIndex);
     void ParseSpaceToDepth(GraphPtr graph, unsigned int layerIndex);
     void ParseSplitter(GraphPtr graph, unsigned int layerIndex);
+    void ParseStack(GraphPtr graph, unsigned int layerIndex);
     void ParseStridedSlice(GraphPtr graph, unsigned int layerIndex);
     void ParseSubtraction(GraphPtr graph, unsigned int layerIndex);
     void ParseSwitch(GraphPtr graph, unsigned int layerIndex);
diff --git a/src/armnnDeserializer/DeserializerSupport.md b/src/armnnDeserializer/DeserializerSupport.md
index 1f51cd3fa0..698340bd31 100644
--- a/src/armnnDeserializer/DeserializerSupport.md
+++ b/src/armnnDeserializer/DeserializerSupport.md
@@ -42,6 +42,7 @@ The Arm NN SDK Deserialize parser currently supports the following layers:
 * SpaceToBatchNd
 * SpaceToDepth
 * Splitter
+* Stack
 * StridedSlice
 * Subtraction
 * Switch
diff --git a/src/armnnSerializer/ArmnnSchema.fbs b/src/armnnSerializer/ArmnnSchema.fbs
index 09187927ae..e3953df83e 100644
--- a/src/armnnSerializer/ArmnnSchema.fbs
+++ b/src/armnnSerializer/ArmnnSchema.fbs
@@ -130,7 +130,8 @@ enum LayerType : uint {
     SpaceToDepth = 40,
     Prelu = 41,
     TransposeConvolution2d = 42,
-    Resize = 43
+    Resize = 43,
+    Stack = 44
 }
 
 // Base layer table to be used as part of other layers
@@ -599,6 +600,17 @@ table ResizeDescriptor {
     dataLayout:DataLayout;
 }
 
+table StackLayer {
+    base:LayerBase;
+    descriptor:StackDescriptor;
+}
+
+table StackDescriptor {
+    axis:uint;
+    numInputs:uint;
+    inputShape:[uint];
+}
+
 union Layer {
     ActivationLayer,
     AdditionLayer,
@@ -643,7 +655,8 @@ union Layer {
     SpaceToDepthLayer,
     PreluLayer,
     TransposeConvolution2dLayer,
-    ResizeLayer
+    ResizeLayer,
+    StackLayer
 }
 
 table AnyLayer {
diff --git a/src/armnnSerializer/Serializer.cpp b/src/armnnSerializer/Serializer.cpp
index 0a9e3353d7..b59bac6041 100644
--- a/src/armnnSerializer/Serializer.cpp
+++ b/src/armnnSerializer/Serializer.cpp
@@ -929,7 +929,21 @@ void SerializerVisitor::VisitStackLayer(const armnn::IConnectableLayer* layer,
                                         const armnn::StackDescriptor& stackDescriptor,
                                         const char* name)
 {
-    throw UnimplementedException("SerializerVisitor::VisitStackLayer not yet implemented");
+    auto stackBaseLayer = CreateLayerBase(layer, serializer::LayerType::LayerType_Stack);
+
+    std::vector<unsigned int> inputShape;
+    for (unsigned int i =0; i < stackDescriptor.m_InputShape.GetNumDimensions(); i++)
+    {
+        inputShape.push_back(stackDescriptor.m_InputShape[i]);
+    }
+
+    auto flatBufferStackDescriptor = CreateStackDescriptor(m_flatBufferBuilder,
+                                                           stackDescriptor.m_Axis,
+                                                           stackDescriptor.m_NumInputs,
+                                                           m_flatBufferBuilder.CreateVector(inputShape));
+
+    auto stackLayer = serializer::CreateStackLayer(m_flatBufferBuilder, stackBaseLayer, flatBufferStackDescriptor);
+    CreateAnyLayer(stackLayer.o, serializer::Layer::Layer_StackLayer);
 }
 
 void SerializerVisitor::VisitStridedSliceLayer(const armnn::IConnectableLayer* layer,
diff --git a/src/armnnSerializer/SerializerSupport.md b/src/armnnSerializer/SerializerSupport.md
index 924bab423f..1d47399376 100644
--- a/src/armnnSerializer/SerializerSupport.md
+++ b/src/armnnSerializer/SerializerSupport.md
@@ -42,6 +42,7 @@ The Arm NN SDK Serializer currently supports the following layers:
 * SpaceToBatchNd
 * SpaceToDepth
 * Splitter
+* Stack
 * StridedSlice
 * Subtraction
 * Switch
diff --git a/src/armnnSerializer/test/SerializerTests.cpp b/src/armnnSerializer/test/SerializerTests.cpp
index 33f10ef435..3d74d88e30 100644
--- a/src/armnnSerializer/test/SerializerTests.cpp
+++ b/src/armnnSerializer/test/SerializerTests.cpp
@@ -2379,6 +2379,65 @@ BOOST_AUTO_TEST_CASE(SerializeSplitter)
     deserializedNetwork->Accept(verifier);
 }
 
+BOOST_AUTO_TEST_CASE(SerializeStack)
+{
+    class StackLayerVerifier : public LayerVerifierBase
+    {
+    public:
+        StackLayerVerifier(const std::string& layerName,
+                           const std::vector<armnn::TensorInfo>& inputInfos,
+                           const std::vector<armnn::TensorInfo>& outputInfos,
+                           const armnn::StackDescriptor& descriptor)
+            : LayerVerifierBase(layerName, inputInfos, outputInfos)
+            , m_Descriptor(descriptor) {}
+
+        void VisitStackLayer(const armnn::IConnectableLayer* layer,
+                             const armnn::StackDescriptor& descriptor,
+                             const char* name) override
+        {
+            VerifyNameAndConnections(layer, name);
+            VerifyDescriptor(descriptor);
+        }
+
+    private:
+        void VerifyDescriptor(const armnn::StackDescriptor& descriptor)
+        {
+            BOOST_TEST(descriptor.m_Axis == m_Descriptor.m_Axis);
+            BOOST_TEST(descriptor.m_InputShape == m_Descriptor.m_InputShape);
+            BOOST_TEST(descriptor.m_NumInputs == m_Descriptor.m_NumInputs);
+        }
+
+        armnn::StackDescriptor m_Descriptor;
+    };
+
+    const std::string layerName("stack");
+
+    armnn::TensorInfo inputTensorInfo ({4, 3, 5}, armnn::DataType::Float32);
+    armnn::TensorInfo outputTensorInfo({4, 3, 2, 5}, armnn::DataType::Float32);
+
+    armnn::StackDescriptor descriptor(2, 2, {4, 3, 5});
+
+    armnn::INetworkPtr network = armnn::INetwork::Create();
+    armnn::IConnectableLayer* const inputLayer1 = network->AddInputLayer(0);
+    armnn::IConnectableLayer* const inputLayer2 = network->AddInputLayer(1);
+    armnn::IConnectableLayer* const stackLayer = network->AddStackLayer(descriptor, layerName.c_str());
+    armnn::IConnectableLayer* const outputLayer = network->AddOutputLayer(0);
+
+    inputLayer1->GetOutputSlot(0).Connect(stackLayer->GetInputSlot(0));
+    inputLayer2->GetOutputSlot(0).Connect(stackLayer->GetInputSlot(1));
+    stackLayer->GetOutputSlot(0).Connect(outputLayer->GetInputSlot(0));
+
+    inputLayer1->GetOutputSlot(0).SetTensorInfo(inputTensorInfo);
+    inputLayer2->GetOutputSlot(0).SetTensorInfo(inputTensorInfo);
+    stackLayer->GetOutputSlot(0).SetTensorInfo(outputTensorInfo);
+
+    armnn::INetworkPtr deserializedNetwork = DeserializeNetwork(SerializeNetwork(*network));
+    BOOST_CHECK(deserializedNetwork);
+
+    StackLayerVerifier verifier(layerName, {inputTensorInfo, inputTensorInfo}, {outputTensorInfo}, descriptor);
+    deserializedNetwork->Accept(verifier);
+}
+
 BOOST_AUTO_TEST_CASE(SerializeStridedSlice)
 {
     class StridedSliceLayerVerifier : public LayerVerifierBase