Enumeration IloSynchronizeMode

The values in this enumeration indicate how Solver should synchronize changes in a model with its search for solutions. In general, you cannot modify the current extracted model during a search. In other words, you cannot change a model while the search is active. A search is active during the call of IloSolver::solve and between a call of IloSolver::startNewSearch and the corresponding call of IloSolver::endSearch. You can change the model only at top level (that is, not nested).

Solver buffers changes you make in a model; the buffered changes are not applied immediately. Certain member functions check that buffer:

• The member function IloSolver::solvechecks the buffer at the beginning of its search.
• The member function IloSolver::startNewSearchchecks the buffer before it begins a new search.

The values of the enumeration IloSynchronize mode serve as parameters to such member functions as IloSolver::startNewSearch.

• IloSynchronizeAndRestart when an instance of IloSolver checks the change buffer, makes the solver discard the current model, discard information about the current search, possibly extract the new model including these changes (if necessary), and restart its search “from scratch.”
• IloSynchronizeAndContinue indicates that the member function IloSolver::startNewSearch should check the buffer for changes in the model before it begins a new search. For example, in this mode, the member function will check for such changes in the model as adding or removing an objective (an instance of IloObjective) or a constraint (an instance of IloConstraint). Then the solver should synchronize those changes with its search results if possible. When this mode is in effect, if it is not possible to take the changes into account without extracting the model again, Solver will throw an exception, IloSolver::IloSynchronizeAndContinueNotPossible .

Example

The following lines highlight changes in the model, buffering, and Solver search.

 IloEnv env;
 IloModel model(env);

 // add extractable objects to model

 IloSolver solver(model);
 solver.solve();

 // modify the model (A)

 solver.startNewSearch(mygoal, mode);
 solver.next();
 solver.endSearch();
 

Solver buffers the changes in part (A). The buffered changes will be taken into account only at top level (not nested).

While part (A) is going on, (that is, while you are making changes to the model), the solver (the instance of IloSolver) is not notified about those changes. Instead, Solver silently buffers the changes that will be checked.