| Summary: | Approved for public release; distribution is unlimited === The first phase of this research demonstrates improvements in the performance of branch-and-price algorithms (B and P) for solving integer programs by (i) stabilizing dual variables during column generation, (ii) performing strong branching, (iii) inserting multiple near-optimal columns from each subproblem, (iv) heuristically improving feasible integer solutions, and by applying several other techniques. Computational testing on generalized-assignment problems shows that solution times decrease over "nave" B and P by as much as 96%; and, some problems that could not be solved by standard branch and bound on the standard model formulation have become easy. In the second phase, this research shows how to solve a class of difficult, stochastic mixed-integer programs using B and P.A new, column-oriented formulation of a stochastic facility-location problem (SFLP), using a scenario representation of uncertainty, provides a vehicle for demonstrating this method's viability. Computational results show that B and P can be orders of magnitude faster than solving the original problem by branch and bound, and this can be true even for single-scenario problems; i.e., for deterministic problems. B and P also solves SFLP exactly when random parameters are modeled through certain continuous probability distributions. In practice, these problems solve more quickly than comparable scenario-based problems.
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