torch.nn.InstanceNorm2d fails at runtime

[wojtke]

🐛 Describe the bug

I found that torch.nn.InstanceNorm2d layer, which by default does not track running mean and var, is failing at runtime. It successfully goes through the lowering process with no errors.

I see that the error is caused by some assert assuming that aten__native_batch_norm_legit_no_stats is in training mode, even if it is not. The same goes for torch.nn.BatchNorm2d with track_running_stats=False.

Minimal case to reproduce:

import torch
from executorch.exir import to_edge

class Model(torch.nn.Module):
  def __init__(self):
    super(Model, self).__init__()
    self.gn = torch.nn.InstanceNorm2d(3)

  def forward(self, x: torch.Tensor):
      return self.gn(x)

model = Model().eval()
sample_inputs = (
   torch.rand(1, 3, 3, 3),
)

aten_dialect = torch.export.export(model, sample_inputs)
edge_program = to_edge(aten_dialect)
print(edge_program.exported_program())
executorch_program = edge_program.to_executorch()

with open("instance_norm.pte", "wb") as file:
    executorch_program.write_to_file(file)

The exported program at edge dialect step:

 ExportedProgram:
    class GraphModule(torch.nn.Module):
        def forward(self, x: "f32[1, 3, 3, 3]"):
             # File: /Users/woj/executorch_main/executorch/test.py:11 in forward, code: return self.gn(x)
            aten_view_copy_default: "f32[1, 3, 3, 3]" = executorch_exir_dialects_edge__ops_aten_view_copy_default(x, [1, 3, 3, 3]);  x = None
            aten__native_batch_norm_legit_no_stats = executorch_exir_dialects_edge__ops_aten__native_batch_norm_legit_no_stats(aten_view_copy_default, None, None, True, 0.1, 1e-05);  aten_view_copy_default = None
            getitem: "f32[1, 3, 3, 3]" = aten__native_batch_norm_legit_no_stats[0];  aten__native_batch_norm_legit_no_stats = None
            aten_view_copy_default_1: "f32[1, 3, 3, 3]" = executorch_exir_dialects_edge__ops_aten_view_copy_default(getitem, [1, 3, 3, 3]);  getitem = None
            return (aten_view_copy_default_1,)

Graph signature: ExportGraphSignature(input_specs=[InputSpec(kind=<InputKind.USER_INPUT: 1>, arg=TensorArgument(name='x'), target=None, persistent=None)], output_specs=[OutputSpec(kind=<OutputKind.USER_OUTPUT: 1>, arg=TensorArgument(name='aten_view_copy_default_1'), target=None)])
Range constraints: {}

I built the runner using:

 rm -rf cmake-out && mkdir cmake-out                       
cmake \
    -DCMAKE_INSTALL_PREFIX=cmake-out \
    -DCMAKE_BUILD_TYPE=Release \
    -DEXECUTORCH_BUILD_EXTENSION_MODULE=ON \
    -DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=ON \
    -DEXECUTORCH_ENABLE_LOGGING=ON \
    -DPYTHON_EXECUTABLE=python \
    -Bcmake-out .

cmake --build cmake-out -j16 --target install --config Release

Then when I run the lowered model:

./cmake-out/executor_runner --model_path instance_norm.pte
I 00:00:00.000259 executorch:executor_runner.cpp:73] Model file instance_norm.pte is loaded.
I 00:00:00.000271 executorch:executor_runner.cpp:82] Using method forward
I 00:00:00.000277 executorch:executor_runner.cpp:129] Setting up planned buffer 0, size 256.
I 00:00:00.000303 executorch:executor_runner.cpp:152] Method loaded.
I 00:00:00.000310 executorch:executor_runner.cpp:162] Inputs prepared.
E 00:00:00.000316 executorch:op_native_batch_norm.cpp:178] Check failed (training == false): Portable kernels only support inference mode!
E 00:00:00.000321 executorch:method.cpp:1068] KernelCall failed at instruction 0:1 in operator aten::_native_batch_norm_legit.no_stats_out: 0x12
E 00:00:00.000326 executorch:method.cpp:1074] arg 0 with type id 1
E 00:00:00.000329 executorch:method.cpp:1074] arg 1 with type id 0
E 00:00:00.000331 executorch:method.cpp:1074] arg 2 with type id 0
E 00:00:00.000333 executorch:method.cpp:1074] arg 3 with type id 5
E 00:00:00.000336 executorch:method.cpp:1074] arg 4 with type id 3
E 00:00:00.000338 executorch:method.cpp:1074] arg 5 with type id 3
E 00:00:00.000340 executorch:method.cpp:1074] arg 6 with type id 1
E 00:00:00.000342 executorch:method.cpp:1074] arg 7 with type id 1
E 00:00:00.000344 executorch:method.cpp:1074] arg 8 with type id 1
E 00:00:00.000346 executorch:method.cpp:1074] arg 9 with type id 9
F 00:00:00.000348 executorch:executor_runner.cpp:170] In function main(), assert failed (status == Error::Ok): Execution of method forward failed with status 0x12
[1]    91328 abort      ./cmake-out/executor_runner --model_path instance_norm.pte

Versions

PyTorch version: 2.5.0.dev20240716
Is debug build: False
CUDA used to build PyTorch: None
ROCM used to build PyTorch: N/A

OS: macOS 14.5 (arm64)
GCC version: Could not collect
Clang version: 15.0.0 (clang-1500.3.9.4)
CMake version: version 3.30.2
Libc version: N/A

Python version: 3.10.14 (main, May  6 2024, 14:42:37) [Clang 14.0.6 ] (64-bit runtime)
Python platform: macOS-14.5-arm64-arm-64bit
Is CUDA available: False
CUDA runtime version: No CUDA
CUDA_MODULE_LOADING set to: N/A
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Apple M3 Pro

Versions of relevant libraries:
[pip3] executorch==0.4.0a0+99e1ae1
[pip3] numpy==1.21.3
[pip3] torch==2.5.0.dev20240716
[pip3] torchaudio==2.4.0.dev20240716
[pip3] torchsr==1.0.4
[pip3] torchvision==0.20.0.dev20240716
[conda] executorch                0.4.0a0+99e1ae1          pypi_0    pypi
[conda] numpy                     1.21.3                   pypi_0    pypi
[conda] torch                     2.5.0.dev20240716          pypi_0    pypi
[conda] torchaudio                2.4.0.dev20240716          pypi_0    pypi
[conda] torchsr                   1.0.4                    pypi_0    pypi
[conda] torchvision               0.20.0.dev20240716          pypi_0    pypi

[manuelcandales]

Thank you for reporting this issue!

I see that the error is caused by some assert assuming that aten__native_batch_norm_legit_no_stats is in training mode, even if it is not.

It's actually the other way around, the assert is asserting training == false, which is being violated, i.e. training is equal to true. Notice in the exported graph, the True argument to executorch_exir_dialects_edge__ops_aten__native_batch_norm_legit_no_stats:

aten__native_batch_norm_legit_no_stats = executorch_exir_dialects_edge__ops_aten__native_batch_norm_legit_no_stats(aten_view_copy_default, None, None, True, 0.1, 1e-05);  aten_view_copy_default = None

The question is: Why did training end up being equal to True, if you are just doing eval?

[JacobSzwejbka]

If you run this under

'''with torch.no_grad():'''

does it still happen?

[wojtke]

If you run this under

'''with torch.no_grad():'''

does it still happen?

The exact same thing happens.

It seems that batch norms with track_running_stats=False or instance norm layers decompose to aten__native_batch_norm_legit_no_stats, which doesn’t use running mean or variance parameters. Because of this, training=True is always set. This doesn’t mean they are in training mode—just that they calculate mean and variance on the fly, similar to LayerNorm. The naming might be confusing, but I guess that’s just how it works. The decomposition that supports the point linked here.

I think it would be best to remove the first assert at https://github.com/pytorch/executorch/blob/caadd81e65bf1240479250124814bc625a13b50c/kernels/portable/cpu/op_native_batch_norm.cpp#L173-L185 Right now, the asserts contradict each other.

[manuelcandales]

@wojtke Oh, like LayerNorm, I see. This makes some sense now. I am the one that added those contradicting asserts. I implemented this op for completeness sake only. I thought the op wasn't meant to be reached during eval time, only during training, because of the assert here Ok, will work on this soon. Thank you for catching and figuring this out!