Faster integer-feasibility in mixed-integer linear programs by branching to force change

  • Authors:
  • Jennifer Pryor;John W. Chinneck

  • Affiliations:
  • Systems and Computer Engineering, Carleton University, Ottawa, Ontario, Canada K1S 5B6;Systems and Computer Engineering, Carleton University, Ottawa, Ontario, Canada K1S 5B6

  • Venue:
  • Computers and Operations Research
  • Year:
  • 2011

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Abstract

Branching in mixed-integer (or integer) linear programming requires choosing both the branching variable and the branching direction. This paper develops a number of new methods for making those two decisions either independently or together with the goal of reaching the first integer-feasible solution quickly. These new methods are based on estimating the probability of satisfying a constraint at the child node given a variable/direction pair. The surprising result is that the first integer-feasible solution is usually found much more quickly when the variable/direction pair with the smallest probability of satisfying the constraint is chosen. This is because this selection forces change in many candidate variables simultaneously, leading to an integer-feasible solution sooner. Extensive empirical results are given.