augmented Lagrangian
A penalty function combined with a multiplier estimate, letting the penalty weight stay fixed instead of growing without bound.
For an equality constraint h(x)=0, the augmented Lagrangian is L_A(x,\nu;\rho)=f(x)+\nu\,h(x)+\frac\rho2h(x)^2, combining the ordinary Lagrangian's multiplier term with a quadratic penalty on the same constraint. Alternating an x-minimization with the multiplier update \nu_{k+1}=\nu_k+\rho\,h(x_k) converges to the true multiplier at a fixed, modest \rho, avoiding plain penalty's need for \rho\to\infty.
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