Tasks

A cptask is represented by three decision variables of type cpvar:

• start representing the starting time of the task
• end representing the ending time of the task
• duration representing the duration of the task

These three structural variables are linked by Xpress Kalis with the following constraint: start + duration = end.

• The starting time variable represents two specific parameters of the task:
  • the Earliest Start Time (EST, represented by the lower bound of the 'start' variable) and its Latest Start Time (LST, represented by the upper bound of the 'start' variable).
• The end variable represents two specific parameters of the task:
  • the Earliest Completion Time (ECT, represented by the lower bound of the 'end' variable) and its Latest Completion Time (LCT, represented by the upper bound of the 'end' variable).
• The duration variable represents two specific parameters of the task:
  • the minimum task duration (Dmin, represented by the lower bound of the 'duration' variable) and the maximum task duration (Dmax, represented by the upper bound of the 'duration' variable).

The picture below illustrates this:

Task attributes can be assigned or retrieved with the following methods:

• getstart
• getend
• getduration
• setduration
• getname
• setname
• is_fixed
• addpredecessors
• setpredecessors
• addsuccessors
• setsuccessors
• setsetuptime