Solved by KFrank in post #6 
              
              
                Hi Miturian! 

I think you’re trying to say something slightly different, so let me 
rephrase it: 
x is a batchSize-2 “input” to the “model”; w is the (scalar) weight 
that defines this very simple “model”. 

Yes. 

Yes, but I think it’s more helpful to think of this as a “tensor” chain 
rule, rathe…