New subspace minimization conjugate gradient methods based on regularization model for unconstrained optimization

In this paper, two new subspace minimization conjugate gradient methods based on p-regularization models are proposed, where a special scaled norm in p-regularization model is analyzed. Different choices of special scaled norm lead to different solutions to the p-regularized subproblem. Based on the analyses of the solutions in a two-dimensional subspace, we derive new directions satisfying the sufficient descent condition. With a modified nonmonotone line search, we establish the global convergence of the proposed methods under mild assumptions. R-linear convergence of the proposed methods is also analyzed. Numerical results show that, for the CUTEr library, the proposed methods are superior to four conjugate gradient methods, which were proposed by Hager and Zhang (SIAM J. Optim. 16(1):170-192, 2005), Dai and Kou (SIAM J. Optim. 23(1):296-320, 2013), Liu and Liu (J. Optim. Theory. Appl. 180(3):879-906, 2019) and Li et al. (Comput. Appl. Math. 38(1):2019), respectively.

Automated summary

This paper proposes two new subspace minimization conjugate gradient methods based on p-regularization models, introducing new solutions by analyzing special scaled norms and deriving new directions in a two-dimensional subspace. The methods exhibit global convergence and are also analyzed for R-linear convergence. Numerical results demonstrate the superiority of the proposed methods over four existing conjugate gradient methods in the CUTEr library.