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\section{Inexact AL Algorithm \label{sec:AL algorithm}}
To solve the equivalent formulation presented in Program~\eqref{eq:minmax}, we propose the inexact augmented Lagrangian algorithm, detailed in Algorithm~\ref{Algo:2}. Iteration $k$ of this algorithm calls a subroutine that finds an approximate stationary point of the augmented Lagrangian $\L_{\b_k}(\cdot,y_k)$ with increasing accuracy of $\epsilon_{k+1}$ (Step 2). The increasing sequence $\{\b_k\}_k$ and the dual update (Steps 4 and 5) are responsible for gradually enforcing the constraints in Program~\eqref{prob:01}. As we will see in the convergence analysis, the particular choice of dual step size $\s_k$ in Algorithm~\ref{Algo:2} ensures that the dual variable $y_k$ remains bounded.
\begin{algorithm}
\label{Algo:2}
Input: Parameters $\rho,\rho',\rho''>0$, initialization $x_{1}\in \RR^d$ such that $\|A(x_1)\|\le \rho$ and $\|x_1\|\le \rho'$, dual initialization $y_0\in \RR^m$ and initial dual step size $\s_1$, a non-decreasing, positive, unbounded sequence $\{\b_k\}_{k\ge 1}$, stopping threshold $\tau$.
\\
For $k=1,2,\ldots$, execute\\
\begin{enumerate}
\item \textbf{(Update tolerance)} $\epsilon_{k+1} = 1/\b_k$.
%\begin{align}
%\beta_k = \frac{\beta_{1}}{\log 2}\sqrt{k}\log^2(k+1) .
%\end{align}
\item \textbf{(Inexact primal solution)} Obtain $x_{k+1}\in \RR^d$ such that $\dist(-\nabla_x \L_{\beta_k} (x_{k+1},y_k), \partial g(x_{k+1}) ) \le \epsilon_{k+1}$.\\
\item \textbf{(Control)} If necessary, project $x_{k+1}$ to ensure that $\|x_{k+1}\|\le \rho'$.\\
\item \textbf{(Update dual step size)}
\begin{align*}
\s_{k+1} & = \s_{1} \min\Big(
\frac{\|A(x_1)\| \log^2 2 }{\|A(x_{k+1})\| (k+1)\log^2(k+2)} ,1
\Big).
\end{align*}
\item \textbf{(Dual ascent step)} $y_{k+1} = y_{k} + \sigma_{k+1}A(x_{k+1})$.
\item \textbf{(Stopping criterion)} If
\begin{align*}
& \dist^2(-\nabla_x \L_{\b_k}(x_{k+1}),\partial g(x_{k+1}) \nonumber\\
& \qquad + \s_{k+1} \|A(x_{k+1})\|^2 \le \tau,
\end{align*}
then quit and return $x_{k+1}$ as an (approximate) stationary point of Program~\eqref{prob:01}.
\end{enumerate}
\caption{Linearized AL for solving Program \eqref{prob:01}}
\end{algorithm}

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