Change the C++ example.

examples/cpp/hello_world/main.cpp

@@ -1,25 +1,44 @@
 #include <iostream>
+#include <torch/script.h>
 #include <torch/torch.h>
 #include <torchvision/vision.h>
-#include <torchvision/models/resnet.h>
 
-int main()
-{
-  auto model = vision::models::ResNet18();
-  model->eval();
+int main() {
+  torch::DeviceType device_type;
+  device_type = torch::kCPU;
 
-  // Create a random input tensor and run it through the model.
-  auto in = torch::rand({1, 3, 10, 10});
-  auto out = model->forward(in);
+  torch::jit::script::Module model;
+  try {
+    std::cout << "Loading model\n";
+    // Deserialize the ScriptModule from a file using torch::jit::load().
+    model = torch::jit::load("resnet18.pt");
+    std::cout << "Model loaded\n";
+  } catch (const torch::Error& e) {
+    std::cout << "error loading the model\n";
+    return -1;
+  } catch (const std::exception& e) {
+    std::cout << "Other error: " << e.what() << "\n";
+    return -1;
+  }
 
-  std::cout << out.sizes();
+  // TorchScript models require a List[IValue] as input
+  std::vector<torch::jit::IValue> inputs;
+
+  // Create a random input tensor and run it through the model.
+  inputs.push_back(torch::rand({1, 3, 10, 10}));
+  auto out = model.forward(inputs);
+  std::cout << out << "\n";
 
   if (torch::cuda::is_available()) {
     // Move model and inputs to GPU
-    model->to(torch::kCUDA);
-    auto gpu_in = in.to(torch::kCUDA);
-    auto gpu_out = model->forward(gpu_in);
+    model.to(torch::kCUDA);
+
+    // Add GPU inputs
+    inputs.clear();
+    torch::TensorOptions options = torch::TensorOptions{torch::kCUDA};
+    inputs.push_back(torch::rand({1, 3, 10, 10}, options));
 
-    std::cout << gpu_out.sizes();
+    auto gpu_out = model.forward(inputs);
+    std::cout << gpu_out << "\n";
   }
 }

examples/cpp/hello_world/trace_model.py

@@ -0,0 +1,13 @@
+import os.path as osp
+
+import torch
+import torchvision
+
+HERE = osp.dirname(osp.abspath(__file__))
+ASSETS = osp.dirname(osp.dirname(HERE))
+
+model = torchvision.models.resnet18(pretrained=False)
+model.eval()
+
+traced_model = torch.jit.script(model)
+traced_model.save("resnet18.pt")

packaging/build_cmake.sh

@@ -98,13 +98,18 @@ fi
 # Compile and run the CPP example
 popd
 cd examples/cpp/hello_world
-
 mkdir build
+
+# Trace model
+python trace_model.py
+cp resnet18.pt build
+
 cd build
 cmake .. -DTorch_DIR=$TORCH_PATH/share/cmake/Torch
 
 if [[ "$OSTYPE" == "msys" ]]; then
     "$script_dir/windows/internal/vc_env_helper.bat" "$script_dir/windows/internal/build_cpp_example.bat" $PARALLELISM
+    mv resnet18.pt Release
     cd Release
 else
     make -j$PARALLELISM