Weight decay, treated here as L2 regularization, modifies parameter estimation by adding a penalty proportional to the sum of squared parameter values to the loss. The penalty makes increasingly large parameters increasingly costly, steering optimization away from exceedingly large estimates. section 2.3.4
Operationally, weight decay connects three steps:
- Begin with a loss function; negative log-likelihood is one example. section 2.3.4
- Add the squared-parameter term to obtain a regularized objective. section 2.3.4
- Use numerical optimization to seek parameter values that balance data fit against parameter magnitude. section 2.3.4
Neural-network estimation
When directly finding the likelihood-maximizing parameters is infeasible, optimize a loss augmented with the L2 penalty; the resulting candidate favors smaller parameter values rather than exceedingly large estimates. section 2.3.4








