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  When should constraints be loosened?

Loosening constraints only makes sense at the end of a resolution for the last courses to be placed. By abandoning a constraint during placement, you run the risk of occupying the last place that would respect all the constraints of another course. It is therefore preferable to first place all courses that can be placed without abandoning constraints and secondly, courses for which a constraint needs to be loosened.
 
Tick the option Loosening and unlock the constraints you wish to relax. You can set the parameters for each constraint.
 
The solver will look for new solutions, taking into account the defined loosening of constraints.