Hi Arpan,
The error you are getting is more or less from here:

  
      github.com
  
  
    pytorch/pytorch/blob/master/aten/src/ATen/native/native_functions.yaml#L358-L365 1

- func: add_.Tensor(Tensor(a!) self, Tensor other, *, Scalar alpha=1) -> Tensor(a!)
  device_check: NoCheck   # TensorIterator
  variants: method
  structured_delegate: add.out
  dispatch:
    SparseCPU, SparseCUDA: add_sparse_
    SparseCsrCPU: add_sparse_csr_
    MkldnnCPU: mkldnn_add_



  
  
    
    
  
  


i.e. that op seems to be for sparse tensors, not quantized ones. Its complaining because it doens’t list QuantizedCPU in the dispatch section of that op. I’m not sure exactly what you are doing for the system to be giving you that error without a full repro since the error doesn’t include the full stack trace. Your code shows the model bus is missing the actual quantization process you are using.
Otherwise, I’d recommend taking another look at the quantization docs/tutorials to make sure you’re doing things in the right order, it can be quite finnicky. That tutorial may be a better place to start and once you understand that, you can apply those techniques to your image classification problem.
tutorials
https://pytorch.org/tutorials/advanced/static_quantization_tutorial.html 13
you can find the other tutorials under Model Optimization in the sidebar within the pytorch tutorials pages.