Hello, Jerry
I have a similar problem, and this is my code error:

UserWarning: must run observer before calling calculate_qparams.                                    Returning default scale and zero point
Returning default scale and zero point "
Traceback (most recent call last):
File “mobile_test.py”, line 122, in 
data_loader,bn_list[0],net_config,device=‘cuda:0’))
File “mobile_test.py”, line 55, in prepare_subnet
torch.quantization.convert(subnet, inplace=True)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/quantization/quantize.py”, line 473, in convert
convert_custom_config_dict=convert_custom_config_dict)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/quantization/quantize.py”, line 508, in _convert
custom_module_class_mapping)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/quantization/quantize.py”, line 508, in _convert
custom_module_class_mapping)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/quantization/quantize.py”, line 508, in _convert
custom_module_class_mapping)
[Previous line repeated 3 more times]
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/quantization/quantize.py”, line 509, in _convert
reassign[name] = swap_module(mod, mapping, custom_module_class_mapping)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/quantization/quantize.py”, line 534, in swap_module
new_mod = mapping[type(mod)].from_float(mod)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/intrinsic/quantized/modules/conv_relu.py”, line 97, in from_float
return super(ConvReLU2d, cls).from_float(mod)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/quantized/modules/conv.py”, line 418, in from_float
return _ConvNd.from_float(cls, mod)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/quantized/modules/conv.py”, line 220, in from_float
return cls.get_qconv(mod, activation_post_process, weight_post_process)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/quantized/modules/conv.py”, line 191, in get_qconv
mod.bias is not None, mod.padding_mode)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/intrinsic/quantized/modules/conv_relu.py”, line 74, in init
padding_mode=padding_mode)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/quantized/modules/conv.py”, line 376, in init
False, _pair(0), groups, bias, padding_mode)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/quantized/modules/conv.py”, line 74, in _init
self.set_weight_bias(qweight, bias_float)
File “/home/yuantian/.local/lib/python3.6/site-packages/torch/nn/quantized/modules/conv.py”, line 384, in set_weight_bias
w, b, self.stride, self.padding, self.dilation, self.groups)
RuntimeError: Didn’t find engine for operation quantized::conv2d_prepack NoQEngine

I try to print the code

torch.backends.quantized.supported_engines
But the result is [None]
And my system is ubuntu