Some Strongly Polynomially Solvable Convex Quadratic Programs with Bounded Variables

This paper begins with a class of convex quadratic programs (QPs) with bounded variables solvable by the parametric principal pivoting algorithm with $\mathcal{O}(n^3)$ strongly polynomial complexity, where $n$ is the number of variables of the problem. Extension of the Hessian class is also discussed. Our research is motivated by a recent reference [7] wherein the efficient solution of a quadratic program with a tridiagonal Hessian matrix in the quadratic objective is needed for the construction of a polynomial-time algorithm for solving an associated sparse variable selection problem. With the tridiagonal structure, the complexity of the QP algorithm reduces to $\mathcal{O}(n^2)$. Our strongly polynomiality results extend previous works of some strongly polynomially solvable linear complementarity problems with a P-matrix [9]; special cases of the extended results include weakly quasi-diagonally dominant problems in addition to the tridiagonal ones.