ILOG OPL Development Studio Language Reference Manual

Why label constraints?You can identify constraints by attaching labels to them. It is the recommended practice butit has a performance cost.Benefits♦Constraint labels enable you to benefit from the expand feature in the IDE Problem Browserto find which constraints are tight in a given application or to find dual variable values inlinear programs. See Understanding the Problem Browser in Getting Started with the IDE.♦You can access the slack and dual values for labeled constraints when a solution is available.See the class IloConstraintIloConstraint in the Reference Manual of ILOGScript Extensions for OPL.♦Only labeled constraints are considered by the relaxation and conflict search process ininfeasible models (see Relaxing infeasible models in IDE Tutorials).CostHowever, labeling constraints has a performance and memory cost which can be significant,especially when a tuple pattern is used as the index. Therefore, you are encouraged to not uselabels for large models or, if you do, at least use tuple indices instead of tuple patterns.More precisely, constraint labels are used in three cases: IDE expand actions, in slack anddual values with solutions, and with relaxation and conflict detection. If you do not need thesethree use cases, you should get rid of the label to speed up the execution and lower memoryconsumption.112I L O G O P L D E V E L O P M E N T S T U D I O L A N G U A G ER E F E R E N C E M A N U A L