提出快速去偏LASSO的新方法,计算效率显著提升。
Fast Debiasing of the LASSO Estimator
- 直接求解去偏矩阵W,避免迭代优化
- 在相同条件下实现闭式解,计算更快
- 适合需要高效高维回归的科研与工程场景
高维稀疏回归中,LASSO估计量虽具良好理论性质,但存在偏差问题。已有方法通过求解凸优化问题计算一个近似逆矩阵M来去偏,但计算成本高。本文重新参数化,直接求解去偏矩阵W := AMᵀ,其理论性能依赖于乘积AMᵀ而非M本身。在传感矩阵每行元素无相关性的额外条件下,给出简洁的闭式解,且优化问题有唯一最优解。数值实验验证了方法有效性。
原文摘要 · Abstract (English)
In high-dimensional sparse regression, the \textsc{Lasso} estimator offers excellent theoretical guarantees but is well-known to produce biased estimates. To address this, \cite{Javanmard2014} introduced a method to ``debias" the \textsc{Lasso} estimates for a random sub-Gaussian sensing matrix $\boldsymbol{A}$. Their approach relies on computing an ``approximate inverse" $\boldsymbol{M}$ of the matrix $\boldsymbol{A}^\top \boldsymbol{A}/n$ by solving a convex optimization problem. This matrix $\boldsymbol{M}$ plays a critical role in mitigating bias and allowing for construction of confidence intervals using the debiased \textsc{Lasso} estimates. However the computation of $\boldsymbol{M}$ is expensive in practice as it requires iterative optimization. In the presented work, we re-parameterize the optimization problem to compute a ``debiasing matrix" $\boldsymbol{W} := \boldsymbol{AM}^{\top}$ directly, rather than the approximate inverse $\boldsymbol{M}$. This reformulation retains the theoretical guarantees of the debiased \textsc{Lasso} estimates, as they depend on the \emph{product} $\boldsymbol{AM}^{\top}$ rather than on $\boldsymbol{M}$ alone. Notably, we provide a simple, computationally efficient, closed-form solution for $\boldsymbol{W}$ under similar conditions for the sensing matrix $\boldsymbol{A}$ used in the original debiasing formulation, with an additional condition that the elements of every row of $\boldsymbol{A}$ have uncorrelated entries. Also, the optimization problem based on $\boldsymbol{W}$ guarantees a unique optimal solution, unlike the original formulation based on $\boldsymbol{M}$. We verify our main result with numerical simulations.
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