Instances of the single machine scheduling problem with preventive maintenance without setup-times (WCT)
The considered objective function for these instances is the weighted sum of completion times \sum_i(Wi*Ci).
Let N be the number of operations and Unif[A, B] a uniform distribution over [A,B]. The processing times Pi and the weights Wi are uniformly distributed over [A,B]. The machine has to indergo a preventive maintenance in each period of time T. D is the duration of the maintenance activity.
The instances generated for the considered problem are divided in four benchmark classes each composed of 52 instances ranging from 2 to 1000 jobs (namely N = 2 to 50, 100, 500 and 1000 jobs) and 15 replications are available for each instance of size N. Moreover D is either set to D=0 (i.e. negligible maintenance duration) or set to D=T*2/100 (i.e. significant maintenance duration, denoted by 2%T). All in all, we have 6240 instances (4 * 52 * 15 * 2).
In each class, the parameters are generated as follows:
- Class 1:
- Pi= Unif[20, 100]
- Wi= Unif[1, N]
- T = max( max(Pi) , 2*average(Pi))
- Class 2:
- Pi= Unif[20, 100]
- Wi= Unif[1, N]
- T = max( max(Pi) , 4*average(Pi))
- Class 3:
- Pi= Unif[25, 50]
- Wi= Unif[1, N]
- T = 100
- Class 4:
- Pi= Unif[25, 50]
- Wi= Unif[1, N]
- T = 150
The instances used in the published work are those belonging to Classes 2 and 3. All instances are available in the zip archive: 
WCT.zip
The name of each instance is composed of 6 fields: dd_<M>_<D>_<N>_<seed>_<C>_<F>.dat Where:
- <M> is the number of machines (= 1 here);
- <D> is the maintenance duration (either 0 or 2%T here);
- <N> is the number of jobs (N = 2 to 50, 100, 500 and 1000 jobs);
- <seed> is the seed that is used to generate each replication;
- <C> is the Class-number (1, 2, 3 or 4);
- <F> is the format (H for raw format, C for "CPLEX-like" format).
In the raw format, each file is composed of 3 lines:
- <N> <D> <T> <T>
- List of (N) Pi values
- List of (N) Wi values
