SGD Parameter Update

Problem Statement

Perform a single Stochastic Gradient Descent update step.

Background

In SGD, parameters are updated using gradients and a learning rate $\alpha$ (alpha):

$W = W - \alpha \cdot dW$

This simple rule moves parameters in the direction that reduces the loss.

Your Task

Write a function sgd_update(weights, gradients, learning_rate) that performs a single SGD update on a list of weights.

Output Format

Return a list of updated weights. Round each value to 4 decimal places.