Function SelectTensorHandleStrategy

src/armnn/Network.cpp:1878–1947

Select the TensorHandleFactories and the corresponding memory strategy

// Select the TensorHandleFactories and the corresponding memory strategy
OptimizationResult SelectTensorHandleStrategy(Graph& optGraph,
                                              BackendsMap& backends,
                                              TensorHandleFactoryRegistry& registry,
                                              bool importEnabled,
                                              bool exportEnabled,
                                              Optional<std::vector<std::string>&> errMessages)
{
    ARMNN_SCOPED_PROFILING_EVENT(Compute::Undefined, "Optimizer_SelectTensorHandleStrategy");
    OptimizationResult result;

    optGraph.ForEachLayer([&backends, &registry, &result, &errMessages, importEnabled, exportEnabled](Layer* layer)
    {
        // Lets make sure the backend is in our list of supported backends. Something went wrong during backend
        // assignment if this check fails
        if (backends.find(layer->GetBackendId()) == backends.end())
        {
            throw armnn::Exception("Backend id not found for the layer");
        }

        // Check each output separately
        for (unsigned int slotIdx = 0; slotIdx < layer->GetNumOutputSlots(); slotIdx++)
        {
            OutputSlot& outputSlot = layer->GetOutputSlot(slotIdx);

            ITensorHandleFactory::FactoryId slotOption = ITensorHandleFactory::LegacyFactoryId;

            // Calculate the factory to use which results in the fewest copies being made.
            switch(layer->GetType())
            {
                case LayerType::Input:
                    slotOption = CalculateSlotOptionForInput(backends, outputSlot, registry, importEnabled);
                    break;
                case LayerType::Output:
                    slotOption = CalculateSlotOptionForOutput(backends, outputSlot, registry);
                    break;
                default:
                    slotOption = CalculateSlotOption(backends, outputSlot, registry, exportEnabled);
                    break;
            }
            outputSlot.SetTensorHandleFactory(slotOption);

            // Now determine the "best" edge strategy for each connection given the slotOption.
            unsigned int connectionIdx = 0;
            for (auto&& connection : outputSlot.GetConnections())
            {
                const Layer& connectedLayer = connection->GetOwningLayer();

                EdgeStrategy strategy = CalculateEdgeStrategy(backends, slotOption, *layer, connectedLayer,
                                                              registry, importEnabled);

                if (strategy == EdgeStrategy::Undefined)
                {
                    result.m_Error = true;
                    if (errMessages)
                    {
                        errMessages.value().emplace_back("Could not find valid strategy required for compatibility"
                                                         " between backends.");
                    }