Unboundedness

A problem is said to be unbounded if the objective function may be improved indefinitely without violating the constraints and bounds. This can happen if a problem is being solved with the wrong optimization sense, e.g., a maximization problem is being minimized. However, when a problem is unbounded and the problem is being solved with the correct optimization sense then this indicates a problem in the formulation of the model or the data. Typically, the problem is caused by missing constraints or the wrong signs on the coefficients. Note that unboundedness is often diagnosed by presolve.