1273137683

Source: wachplan.zpl
File: upload/06.05.2010_1273137683_Sebastian_Orlowski/wachplan.zpl
Name: Sebastian_Orlowski
Company: atesio GmbH
eMail: orlowski@atesio.de
Street: Bundesallee 89
City: Berlin
Country: Germany
Message: I constructed this shift plan optimization model for a sail training trip in 2007. The task is to assign crew members to shifts such that everybody has a shift with everybody else at least once (to improve contact among the crew members), all shifts have 2 or 3 crew members, and all crew members have the same total number of shifts during the trip. This number is maximized to maximize the training effect. The number of shifts with two persons is limited because the guys would get too little sleep.

The optimal solution (number of shifts per person) is 8. All three solvers scip-1.2, cplex-12.1, and gurobi-3.0 find the optimal solution immediately, but fail to prove optimality for a long time with the default settings. The dual bound remains at the initial LP value 9 during the whole optimization. SCIP/cplex proves optimality within 6 hours (on opt58 at ZIB, 3 MHz CPU, 8 MB memory), Gurobi within 2 hours, and cplex is still running after 14 hours.


delivered on: 06.05.2010
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