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Solving Massive Stochastic Programs with Benders' Decomposition

Towards Data Science •
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Stochastic programming often fails in production because the deterministic equivalent grows too large for standard solvers. When developers add thousands of scenarios to account for uncertainty, the resulting block-angular constraint matrix creates a memory bottleneck. This scaling issue makes traditional linear programming solvers like Gurobi or HiGHS struggle as runtime increases superlinearly.

Benders' decomposition solves this by treating the first-stage decision as a complicating variable. Instead of solving one giant problem, the algorithm guesses a decision and solves independent scenario subproblems in parallel. It uses LP duality to generate linear cuts that refine the first-stage guess, iteratively approximating the convex recourse cost function.

This approach is essential for high-stakes engineering tasks like hydropower scheduling and supply-chain planning. By decoupling the scenarios, engineers can handle models that are too large to even enumerate. The method transforms a monolithic, memory-heavy task into a series of manageable subproblems that converge on an optimal solution.