backpropagation

A build-it-yourself check on recurrent forward passes and backprop through time. What matters is the shared-weight recurrence, summing gradients over timesteps, and articulating the vanishing-gradient problem. The code follows.

A build-it-yourself check on how PyTorch actually works under the hood. What matters is assembling a computation graph during the forward pass, local derivatives per op, and a topological-order backward pass that accumulates gradients. Below is a minimal engine.

Backprop is the algorithm that makes deep learning trainable, and the interviewer wants the chain-rule mechanics, not just 'it computes gradients.' What interviewers reward is the forward-then-backward flow and why it is efficient. Here is the answer.