Using goals

IBM ILOG Solver User's Manual > Extending the Library > Writing a Goal: Car Sequencing > Understanding goals > Using goals

Using goals

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The member functions IloSolver::solve and IloSolver::next control the execution of goals. The first time one of these member functions is called, it creates a stack of goals, called the goal stack.

Note

Goals must be called by IloSolver::solve, IloSolver::next, or by other goals. Otherwise, they are not executed.

Defining a goal creates two functions:

The first one creates the goal. The name of this function is the name of the goal, and its parameters are those used to define the goal.
The second function is a virtual function used to execute the goal. Its name is execute. Its body is the body used in the definition of the goal. When this function is used, the goal is executed.

A goal is passed as a parameter to the member functions IloSolver::solve or IloSolver::next. These functions push a goal onto the goal stack of the invoking solver; when that occurs, the goal is called.

Thus, each time a goal is called, it is added on top of this stack, but it is not executed immediately. When the current goal execution is finished, the member function IloSolver::solve or IloSolver::next pops the goal which is on top of the goal stack, if any, and executes it. Thus goals are executed first in, last out. If the goal stack is empty, the call to solve or next terminates and returns IlcTrue.

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