“…The orthogonality-constrained minimization problem ( 1) is widely applicable in many fields, such as the nearest low-rank correlation matrix problem [2,3], the linear eigenvalue problem [4][5][6], sparse principal component analysis [5,7], Kohn-Sham total energy minimization [4,6,8,9], low-rank matrix completion [10], the orthogonal Procrustes problem [8,11], maximization of sums of heterogeneous quadratic functions from statistics [4,12,13], the joint diagonalization problem [13], dimension reduction techniques in pattern recognition [14], and deep neural networks [15,16], among others.…”