Comment by pkhuong

It's classic Lin Kernighan (http://webhotel4.ruc.dk/~keld/research/LKH/) for the primal heuristic, and optimality proof by Concorde for cutting plane generation and branching (https://www.math.uwaterloo.ca/tsp/book/index.html, or https://www.math.uwaterloo.ca/tsp/korea/computation.html for details specific to this instance), with CPLEX as the underlying LP solver.