/// <summary>
/// Given a problem with precedence arcs as a DAG. Creates an assignment by iterating jobs over machines. Very naive.
/// </summary>
public void MakeRollingMachineAssignment()
{
AssignmentDescription = "Rolling Machine Assignment";
if (PrecedenceDAG.N <= 1)
{
throw new Exception("No DAG given. Cannot build schedule without problem instance");
}
int NJobsAssigned = 0;
int[] nParentsProcessed = new int[PrecedenceDAG.N + 1];
Queue <Job> AllPredDone = new Queue <Job>(); // The jobs that will no longer change Rj are those for which all Parents have been considered.
foreach (Job j in PrecedenceDAG.Jobs) //All jobs without predecessors can know their final Rj (it is equal to their own rj).
{
if (j.Predecessors.Count == 0)
{
AllPredDone.Enqueue(j);
}
}
int CandidateMachineID = 0;
while (AllPredDone.Count > 0)
{
bool DebugAssignmentSuccess = false;
CandidateMachineID++;
if (CandidateMachineID >= Machines.Count + 1)
{
CandidateMachineID = 1;
}
Job CurrentJob = AllPredDone.Dequeue();
for (int i = 0; i < Machines.Count; i++)
{
if (!IsFeasibleAssignment(CurrentJob, GetMachineByID(CandidateMachineID)))
{
// try the next machine:
CandidateMachineID++;
if (CandidateMachineID >= Machines.Count)
{
CandidateMachineID = 0;
}
}
else
{
// assign to that machine
//IMPORTANT: Update the Queue before adding any arcs, or things may be added to the queue twice:
foreach (Job Succ in CurrentJob.Successors)
{
nParentsProcessed[Succ.ID]++;
if (nParentsProcessed[Succ.ID] == Succ.Predecessors.Count)
{
AllPredDone.Enqueue(Succ);
}
}
//IMPORTANT: Only do this after the queue has been updated.
// if it is the first job on the machine, no precedence arc is needed:
if (GetMachineByID(CandidateMachineID).AssignedJobs.Count > 0)
{
PrecedenceDAG.AddArc(GetMachineByID(CandidateMachineID).LastJob(), CurrentJob);
}
//IMPORTANT: Only do this after the queue has been updated and after machine arcs have been updated
AssignJobToMachine(CurrentJob, GetMachineByID(CandidateMachineID));
DebugAssignmentSuccess = true;
break;
}
}
if (!DebugAssignmentSuccess)
{
throw new Exception("Schedulde.Build was unable to create a feasible schedule: the algorithm is bugged.");
}
NJobsAssigned++;
}
if (NJobsAssigned < PrecedenceDAG.N)
{
throw new Exception("Not all jobs assigned");
}
}
