Hello Forum!
I noticed that jit “quit working” on a particular use case with the
1.8.0.dev20201203 nightly build.
Specifically, a function that showed an about 2x jit speed-up with
version 1.6.0 shows no speed-up with version 1.8.0.
Details can be found in this post:

  
    
    
    How to implement efficient element-wise 'ax+b' function 
  
  
    Hi Zhi and Alex! 

The short story is that I can reproduce your results. 
I’ve also done some further experimentation. 

The best I could come up with was to apply Alex’s torchscript suggestion 
to your “w-b” version. 
I also tried a Conv2d version – even though it doesn’t have 
BatchNorm2d's normalization step, it was also slower. 
Note, torchscript gave a nice speedup with pytorch version 1.6.0, but 
not with a version 1.8.0 nightly build. 
I used your original problem – same-shaped tensors, a…
  


Best.
K. Frank