In the Concert Technology Library, crossover is specified in the method that invokes the optimizer.

In the Interactive Optimizer, options to the baropt command control whether the ILOG CPLEX Barrier Optimizer stops with a nonbasic solution or crosses over to a simplex optimizer to generate a basic solution. Table 4.8 summarizes those options to the baropt command in the Interactive Optimizer.

Table 4.9 shows you the corresponding routines from the Callable Library.

When you use the ILOG CPLEX Barrier Optimizer with no crossover (for example, with the command baropt stop), you can save the primal and dual variable values and their associated reduced cost and dual values in a VEC-format file. You can then read that VEC file into ILOG CPLEX before you initiate a crossover at a later time. After you read a VEC file into ILOG CPLEX, all three optimizers-primal simplex, dual simplex, and barrier simplex-automatically invoke crossover.

Even if you have set the advanced basis indicator to no (meaning that you do not intend to start from an advanced basis), ILOG CPLEX automatically resets the indicator to yes when it reads a VEC file. If you turn off the advanced basis indicator after reading a VEC file, then the simplex optimizers will honor this setting and will not initiate crossover.