IVGCVSW-2458 Refactor the Optimize function (Network.cpp) so that

subgraphs are optimized by the backends

 * Added a new method OptimizeSubGraph to the backend interface
 * Refactored the Optimize function so that the backend-specific
   optimization is performed by the backend itself (through the new
   OptimizeSubGraph interface method)
 * Added a new ApplyBackendOptimizations function to apply the new
   changes
 * Added some new convenient constructors to the SubGraph class
 * Added AddLayer method and a pointer to the parent graph to the
   SubGraph class
 * Updated the sub-graph unit tests to match the changes
 * Added SelectSubGraphs and ReplaceSubGraphConnections overloads
   that work with sub-graphs
 * Removed unused code and minor refactoring where necessary

Change-Id: I46181794c6a9e3b10558944f804e06a8f693a6d0

1 files changed, 46 insertions, 17 deletions

diff --git a/src/armnn/Graph.cpp b/src/armnn/Graph.cpp
index 831d85e404..1bd4fbd85a 100644
--- a/src/armnn/Graph.cpp
+++ b/src/armnn/Graph.cpp
@@ -2,7 +2,9 @@
 // Copyright © 2017 Arm Ltd. All rights reserved.
 // SPDX-License-Identifier: MIT
 //
+
 #include "Graph.hpp"
+#include "SubGraph.hpp"
 #include "LayersFwd.hpp"
 
 #include <armnn/Utils.hpp>
@@ -17,7 +19,6 @@
 #include <DotSerializer.hpp>
 #include <sstream>
 
-
 namespace armnn
 {
 
@@ -238,7 +239,7 @@ const Graph& Graph::TopologicalSort() const
             it->ResetPriority();
         }
 
-        auto compareLayerPriority = [](const LayersList::value_type& layerA, const LayersList::value_type& layerB)
+        auto compareLayerPriority = [](const LayerList::value_type& layerA, const LayerList::value_type& layerB)
             {
                 return layerA->GetPriority() < layerB->GetPriority();
             };
@@ -306,44 +307,72 @@ void Graph::SubstituteSubGraph(std::unique_ptr<SubGraph> subGraph, IConnectableL
     EraseSubGraphLayers(*subGraph);
 }
 
+void Graph::SubstituteSubGraph(std::unique_ptr<SubGraph> subGraph, const SubGraph& substituteSubGraph)
+{
+    BOOST_ASSERT(subGraph);
+
+    ReplaceSubGraphConnections(*subGraph, substituteSubGraph);
+    EraseSubGraphLayers(*subGraph);
+}
+
 void Graph::ReplaceSubGraphConnections(const SubGraph& subGraph, IConnectableLayer* substituteLayer)
 {
     BOOST_ASSERT(substituteLayer != nullptr);
     BOOST_ASSERT_MSG(std::find(m_Layers.begin(), m_Layers.end(), substituteLayer) != m_Layers.end(),
-                     "Substitue layer is not a member of graph");
+                     "Substitute layer is not a member of graph");
+
+    SubGraph substituteSubGraph(subGraph, substituteLayer);
+    ReplaceSubGraphConnections(subGraph, substituteSubGraph);
+}
+
+void Graph::ReplaceSubGraphConnections(const SubGraph& subGraph, const SubGraph& substituteSubGraph)
+{
+    BOOST_ASSERT_MSG(!substituteSubGraph.GetLayers().empty(), "New sub-graph used for substitution must not be empty");
+
+    const SubGraph::Layers& substituteSubGraphLayers = substituteSubGraph.GetLayers();
+    std::for_each(substituteSubGraphLayers.begin(), substituteSubGraphLayers.end(), [&](Layer* layer)
+    {
+        BOOST_ASSERT_MSG(std::find(m_Layers.begin(), m_Layers.end(), layer) != m_Layers.end(),
+                         "Substitute layer is not a member of graph");
+    });
 
     const SubGraph::InputSlots& subGraphInputSlots = subGraph.GetInputSlots();
     const SubGraph::OutputSlots& subGraphOutputSlots = subGraph.GetOutputSlots();
 
-    const unsigned int numInputSlots = boost::numeric_cast<unsigned int>(subGraphInputSlots.size());
-    const unsigned int numOutputSlots = boost::numeric_cast<unsigned int>(subGraphOutputSlots.size());
+    unsigned int subGraphNumInputSlots = boost::numeric_cast<unsigned int>(subGraphInputSlots.size());
+    unsigned int subGraphNumOutputSlots = boost::numeric_cast<unsigned int>(subGraphOutputSlots.size());
+
+    const SubGraph::InputSlots& substituteSubGraphInputSlots = substituteSubGraph.GetInputSlots();
+    const SubGraph::OutputSlots& substituteSubGraphOutputSlots = substituteSubGraph.GetOutputSlots();
+
+    BOOST_ASSERT(subGraphNumInputSlots == substituteSubGraphInputSlots.size());
+    BOOST_ASSERT(subGraphNumOutputSlots == substituteSubGraphOutputSlots.size());
 
-    BOOST_ASSERT(numInputSlots == substituteLayer->GetNumInputSlots());
-    BOOST_ASSERT(numOutputSlots == substituteLayer->GetNumOutputSlots());
+    // Disconnect the sub-graph and replace it with the substitute sub-graph
 
-    // Disconnect the sub-graph and replace it with the substitute layer
     // Step 1: process input slots
-    for(unsigned int inputSlotIdx = 0u; inputSlotIdx < numInputSlots; ++inputSlotIdx)
+    for (unsigned int inputSlotIdx = 0; inputSlotIdx < subGraphNumInputSlots; ++inputSlotIdx)
     {
         InputSlot* subGraphInputSlot = subGraphInputSlots.at(inputSlotIdx);
-        BOOST_ASSERT(subGraphInputSlot != nullptr);
+        BOOST_ASSERT(subGraphInputSlot);
 
         IOutputSlot* connectedOutputSlot = subGraphInputSlot->GetConnection();
-        BOOST_ASSERT(connectedOutputSlot != nullptr);
+        BOOST_ASSERT(connectedOutputSlot);
         connectedOutputSlot->Disconnect(*subGraphInputSlot);
 
-        IInputSlot& substituteInputSlot = substituteLayer->GetInputSlot(inputSlotIdx);
-        connectedOutputSlot->Connect(substituteInputSlot);
+        IInputSlot* substituteInputSlot = substituteSubGraphInputSlots.at(inputSlotIdx);
+        BOOST_ASSERT(substituteInputSlot);
+        connectedOutputSlot->Connect(*substituteInputSlot);
     }
 
     // Step 2: process output slots
-    for(unsigned int outputSlotIdx = 0u; outputSlotIdx < numOutputSlots; ++outputSlotIdx)
+    for(unsigned int outputSlotIdx = 0; outputSlotIdx < subGraphNumOutputSlots; ++outputSlotIdx)
     {
         OutputSlot* subGraphOutputSlot = subGraphOutputSlots.at(outputSlotIdx);
-        BOOST_ASSERT(subGraphOutputSlot != nullptr);
+        BOOST_ASSERT(subGraphOutputSlot);
 
-        OutputSlot* substituteOutputSlot = boost::polymorphic_downcast<OutputSlot*>(
-                &substituteLayer->GetOutputSlot(outputSlotIdx));
+        OutputSlot* substituteOutputSlot = substituteSubGraphOutputSlots.at(outputSlotIdx);
+        BOOST_ASSERT(substituteOutputSlot);
         subGraphOutputSlot->MoveAllConnections(*substituteOutputSlot);
     }
 }