A modified Schur complement method for handling dense columns in interior point methods for linear programming

Knud D. Andersen

The main computational work in interior point methods for linear programming (LP) is to find a solution of a least squares problem. Usually this is solved using the normal-equations approach. However, if the LP constraint matrix contains a nearly dense column the normal equations will be nearly dense. Consequently for large sparse LP problems it will be extremely expensive to solve the normal equations. In this paper we propose a modified Schur-complement method to handle dense columns which has some desirable properties compared to the original Schur complement method. Encouraging numerical results are presented.


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