Torch::jit::load fails with Unknown Type Name Error

I am trying to implement Fast Neural Style Transfer on iOS application. To do that, I started with an implemented version of Fast Neural Style Transfer from here and attempt to follow Pytorch Mobile tutorial by @xta0 to run the model on my device.

After generating the file, I tried to load it following the tutorial code using TorchModule. However, I got this error when loading the module.

Unknown type name ‘torch.torch.classes.xnnpack.TransposeConv2dOpContext’: Serialized File “code/torch/transformer/”, line 18
annotations[“prepack_folding._jit_pass_packed_weight_11”] = torch.torch.classes.xnnpack.Conv2dOpContext annotations[“prepack_folding._jit_pass_packed_weight_12”] = torch.torch.classes.xnnpack.Conv2dOpContext annotations[“prepack_folding._jit_pass_packed_weight_13”] = torch.torch.classes.xnnpack.TransposeConv2dOpContext ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <— HERE
annotations[“prepack_folding._jit_pass_packed_weight_14”] = torch.torch.classes.xnnpack.TransposeConv2dOpContext annotations[“prepack_folding._jit_pass_packed_weight_15”] = torch.torch.classes.xnnpack.Conv2dOpContext (lldb)

Within Xcode, the code fails here

    private lazy var module: TorchModule = {
    // Verified that filePath exist.
    if let filePath = Bundle.main.path(forResource: "mobile_model2", ofType: "pt"),
        // The problem is at TorchModule init setup.
        let module = TorchModule(fileAtPath: filePath) {
        return module
    } else {
        fatalError("Can't find the model file!")

Code fails specifically at torch::jit::load

- (nullable instancetype)initWithFileAtPath:(NSString*)filePath {
  self = [super init];
  if (self) {
    try {
      // CODE FAILS HERE, when trying to load!
      _impl = torch::jit::load(filePath.UTF8String);
    } catch (const std::exception& exception) {
      NSLog(@"%s", exception.what());
      return nil;
  return self;

This means that the C++ load method call wasn’t able to load my What could possibly caused this?

In order to verify that this issue is not solely caused by my model, I tried loading this with another pretrained model resnet18. And as expected, I also receive errors while attempting to load this model using TorchModule, although with a different set of errors.

**Unknown builtin op: aten::_add_relu_.**

**Could not find any similar ops to aten::_add_relu_. This op may not exist or may not be currently supported in TorchScript.**

I have the same issue, Pytorch-android 1.8.1 build from source. model exported by pytorch 1.8.1. have you solved this problem?

I think the issue is with the builds. Probably ops are not linked in. @xta0 any idea what might be the issue. @IvanKobzarev on the android side.

@hangrymangry what’s your pytorch version? Are you using cocoapods or building from source? @kimishpatel TransposeConv2dOpContext is from the xnnpack rewrite, right?

Yes it is from xnnpack but likely the issue with op registration since, as mentioned, even aten::_add_relu_ cannot be found.