Interval variables for scheduling in minizinc with IBM CP optimizer

[Kim Van den Houten]

Hi all,

I am interested in switching from IBM native language to Minizinc, however, I am unsure about how interval variables would work. I read on a Github page (https://github.com/IBMDecisionOptimization/cpofzn/tree/master/mznlib) that interval variables defined in Minizinc will be transformed to integer variables in IBM which is suboptimal for scheduling taksk. Could someone help me out?

I am particularly interested in models for RCPSP and/or RCPSP/max. 

Kim 

Delft University of Technology

[Jip Dekker]

Hi Kim,

MiniZinc doesn't have explicit interval variables. Intervals are generally represented using two integer variables (start time + duration or start + end time). With newer versions of MiniZinc you can actually create tuples or records to represent intervals.

In communication to the solver these variables are not necessarily connected, but I would assume that solvers like IBM CPOptimizer can reconstruct these variables when used in scheduling global constraint, such as disjunctive or cummulative.

Cheers,

Jip