dnn(ie): switch to nGraph backend by default

modules/dnn/CMakeLists.txt

@@ -92,7 +92,7 @@ endif()
 
 set(dnn_runtime_libs "")
 if(INF_ENGINE_TARGET)
-  ocv_option(OPENCV_DNN_IE_NN_BUILDER_2019 "Build with Inference Engine NN Builder API support" ON)
+  ocv_option(OPENCV_DNN_IE_NN_BUILDER_2019 "Build with Inference Engine NN Builder API support" ON)  # future: NOT HAVE_NGRAPH
   if(OPENCV_DNN_IE_NN_BUILDER_2019)
     message(STATUS "DNN: Enabling Inference Engine NN Builder API support")
     add_definitions(-DHAVE_DNN_IE_NN_BUILDER_2019=1)

modules/dnn/include/opencv2/dnn/dnn.hpp

@@ -47,9 +47,9 @@
 #include "opencv2/core/async.hpp"
 
 #if !defined CV_DOXYGEN && !defined CV_STATIC_ANALYSIS && !defined CV_DNN_DONT_ADD_EXPERIMENTAL_NS
-#define CV__DNN_EXPERIMENTAL_NS_BEGIN namespace experimental_dnn_34_v16 {
+#define CV__DNN_EXPERIMENTAL_NS_BEGIN namespace experimental_dnn_34_v17 {
 #define CV__DNN_EXPERIMENTAL_NS_END }
-namespace cv { namespace dnn { namespace experimental_dnn_34_v16 { } using namespace experimental_dnn_34_v16; }}
+namespace cv { namespace dnn { namespace experimental_dnn_34_v17 { } using namespace experimental_dnn_34_v17; }}
 #else
 #define CV__DNN_EXPERIMENTAL_NS_BEGIN
 #define CV__DNN_EXPERIMENTAL_NS_END

modules/dnn/src/op_inf_engine.cpp

@@ -41,11 +41,13 @@ static const char* dumpInferenceEngineBackendType(Backend backend)
 Backend& getInferenceEngineBackendTypeParam()
 {
     static Backend param = parseInferenceEngineBackendType(
-        utils::getConfigurationParameterString("OPENCV_DNN_BACKEND_INFERENCE_ENGINE_NN_BUILDER_2019_TYPE",
+        utils::getConfigurationParameterString("OPENCV_DNN_BACKEND_INFERENCE_ENGINE_TYPE",
-#ifndef HAVE_DNN_IE_NN_BUILDER_2019
+#ifdef HAVE_DNN_NGRAPH
             CV_DNN_BACKEND_INFERENCE_ENGINE_NGRAPH
-#else
+#elif defined(HAVE_DNN_IE_NN_BUILDER_2019)
             CV_DNN_BACKEND_INFERENCE_ENGINE_NN_BUILDER_API
+#else
+#error "Build configuration error: nGraph or NN Builder API backend should be enabled"
 #endif
         )
     );