public virtual bool Expand(CbsNode node, CbsConflict conflict)
{
if (runner.ElapsedMilliseconds() > Constants.MAX_TIME)
{
return(false);
}
highLevelExpanded++;
if (conflict == null)
{
this.totalCost = node.totalCost;
this.goalNode = node;
this.solution = node.CalculateJointPlan();
this.Clear();
return(true);
}
CbsNode toAdd;
CbsConstraint con2 = new CbsConstraint(conflict, instance, false);
CbsConstraint con1 = new CbsConstraint(conflict, instance, true);
byte stepLength = 0;
if (conflict.vertex)
{
stepLength = 1;
}
bool ok1 = false, ok2 = false;
if (node.totalCost + conflict.timeStep + stepLength - node.PathLength(conflict.agentA) <= fBound)
{
ok1 = true;
if (node.DoesMustConstraintAllow(con1))
{
toAdd = new CbsNode(node, con1, conflict.agentA);
toAdd.SetMustConstraint(con2);
if (toAdd.Replan3b(conflict.agentA, Math.Max(minCost, conflict.timeStep)))
{
this.highLevelGenerated++;
if (toAdd.totalCost <= fBound)
{
if (Expand(toAdd, toAdd.GetConflict()))
{
return(true);
}
}
else if (toAdd.totalCost < nextF)
{
nextF = toAdd.totalCost;
}
}
}
}
if (node.totalCost + conflict.timeStep + stepLength - node.PathLength(conflict.agentB) <= fBound)
{
ok2 = true;
if (node.DoesMustConstraintAllow(con2))
{
toAdd = new CbsNode(node, con2, conflict.agentB);
toAdd.SetMustConstraint(con1);
if (toAdd.Replan3b(conflict.agentB, Math.Max(minCost, conflict.timeStep)))
{
this.highLevelGenerated++;
if (toAdd.totalCost <= fBound)
{
if (Expand(toAdd, toAdd.GetConflict()))
{
return(true);
}
}
else if (toAdd.totalCost < nextF)
{
nextF = toAdd.totalCost;
}
}
}
}
if (ok1 && ok2)
{
toAdd = new CbsNode(node, con1, conflict.agentA);
if (toAdd.Replan3b(conflict.agentA, Math.Max(minCost, conflict.timeStep)))
{
if (toAdd.totalCost <= fBound)
{
toAdd = new CbsNode(toAdd, con2, conflict.agentB);
if (toAdd.Replan(conflict.agentB, Math.Max(minCost, conflict.timeStep)))
// FIXME: Should this really use the regular Replan() or was this a typo?
{
this.highLevelGenerated++;
if (toAdd.totalCost <= fBound)
{
if (Expand(toAdd, toAdd.GetConflict()))
{
return(true);
}
}
else if (toAdd.totalCost < nextF)
{
nextF = toAdd.totalCost;
}
}
}
}
}
return(false);
}
public virtual void Expand(CbsNode node)
{
CbsConflict conflict = node.GetConflict();
CbsNode child;
if (this.mergeThreshold != -1 && ShouldMerge(node))
{
child = new CbsNode(node, node.agentsGroupAssignment[conflict.agentA], node.agentsGroupAssignment[conflict.agentB]);
if (closedList.ContainsKey(child) == false) // We may have already merged these agents in the parent
{
if (debug)
{
Debug.WriteLine("Merging agents {0} and {1}", conflict.agentA, conflict.agentB);
}
closedList.Add(child, child);
bool success = child.Replan(conflict.agentA, this.minDepth); // or agentB. Doesn't matter - they're in the same group.
if (debug)
{
Debug.WriteLine("New cost: " + child.totalCost);
var constraints = child.GetConstraints();
Debug.WriteLine(constraints.Count + " Remaining internal constraints:");
foreach (CbsConstraint constraint in constraints)
{
Debug.WriteLine(constraint);
}
var externalConstraints = (HashSet_U <CbsConstraint>) this.instance.parameters[CBS_LocalConflicts.CONSTRAINTS];
Debug.WriteLine(externalConstraints.Count.ToString() + " external constraints: ");
foreach (CbsConstraint constraint in externalConstraints)
{
Debug.WriteLine(constraint);
}
Debug.WriteLine("New conflict: " + child.GetConflict());
Debug.Write("New agent group assignments: ");
for (int i = 0; i < child.agentsGroupAssignment.Length; i++)
{
Debug.Write(" " + child.agentsGroupAssignment[i]);
}
Debug.WriteLine("");
Debug.Write("Single agent costs: ");
for (int i = 0; i < child.allSingleAgentCosts.Length; i++)
{
Debug.Write(" " + child.allSingleAgentCosts[i]);
}
Debug.WriteLine("");
child.CalculateJointPlan().PrintPlan();
Debug.WriteLine("");
Debug.WriteLine("");
}
this.maxSizeGroup = Math.Max(this.maxSizeGroup, child.replanSize);
if (success == false) // A timeout probably occured
{
return;
}
if (node.totalCost <= maxCost) // FIXME: Code dup with other new node creations
{
openList.Add(child);
this.highLevelGenerated++;
this.addToGlobalConflictCount(child.GetConflict());
}
}
else
{
closedListHits++;
}
return;
}
// Expand node, possibly partially:
// Generate left child:
int agentAGroupSize = node.GetGroupSize(node.agentsGroupAssignment[conflict.agentA]);
if (node.agentAExpansion == CbsNode.ExpansionState.NOT_EXPANDED && conflict.vertex == true &&
conflict.timeStep >= node.allSingleAgentCosts[conflict.agentA] && // TODO: Consider checking directly whether at the time of the conflict the agent would be at its goal according to the node.singleAgentPlans. It may be more readable.
agentAGroupSize == 1)
// Conflict happens when or after agent A reaches its goal, and agent A is in a single agent group.
// With multi-agent groups, banning the goal doesn't guarantee a higher cost solution,
// since if an agent is forced to take a longer route it may enable another agent in the group
// to take a shorter route, getting an alternative solution of the same cost
// The left child would cost a lot because:
// A) All WAIT moves in the goal before leaving it now add to the g.
// B) We force the low level to compute a path longer than the optimal,
// and with a bad suprise towards the end in the form of a constraint,
// so the low-level's SIC heuristic performs poorly.
// C) We're banning the GOAL from all directions (since this is a vertex conflict),
// so any alternative plan will at least cost 1 more.
// We're ignoring edge conflicts because they can only happen at the goal when reaching it,
// and aren't guaranteed to increase the cost because the goal can still be possibly reached from another edge.
{
if (debug)
{
Debug.WriteLine("Skipping left child");
}
node.agentAExpansion = CbsNode.ExpansionState.DEFERRED;
int agentAOldCost = node.allSingleAgentCosts[conflict.agentA];
// Add the minimal delta in the child's cost:
// since we're banning the goal at conflict.timeStep, it must at least do conflict.timeStep+1 steps
node.totalCost += (ushort)(conflict.timeStep + 1 - agentAOldCost);
openList.Add(node); // Re-insert node into open list with higher cost, don't re-increment global conflict counts
this.partialExpansions++;
}
else if (node.agentAExpansion != CbsNode.ExpansionState.EXPANDED)
// Agent A expansion already skipped in the past or not forcing A from its goal - finally generate the child:
{
if (debug)
{
Debug.WriteLine("Generating left child");
}
var newConstraint = new CbsConstraint(conflict, instance, true);
child = new CbsNode(node, newConstraint, conflict.agentA);
if (closedList.ContainsKey(child) == false)
{
closedList.Add(child, child);
if (child.Replan(conflict.agentA, this.minDepth)) // The node takes the max between minDepth and the max time over all constraints.
{
if (child.totalCost < node.totalCost && agentAGroupSize == 1)
{
Debug.WriteLine("");
Debug.Write("Single agent costs: ");
for (int i = 0; i < child.allSingleAgentCosts.Length; i++)
{
Debug.Write(" " + child.allSingleAgentCosts[i]);
}
Debug.WriteLine("");
//Debug.WriteLine("Offending plan:");
//child.CalculateJointPlan().PrintPlan();
Debug.WriteLine("Chlid plan: (cost {0})", child.allSingleAgentCosts[conflict.agentA]);
child.allSingleAgentPlans[conflict.agentA].PrintPlan();
Debug.WriteLine("Parent plan: (cost {0})", node.allSingleAgentCosts[conflict.agentA]);
node.allSingleAgentPlans[conflict.agentA].PrintPlan();
Debug.Assert(false, "Single agent node with lower cost than parent! " + child.totalCost + " < " + node.totalCost);
}
if (child.totalCost <= this.maxCost)
{
openList.Add(child);
this.highLevelGenerated++;
addToGlobalConflictCount(child.GetConflict());
if (debug)
{
Debug.WriteLine("Child cost: " + child.totalCost);
Debug.WriteLine("Child hash: " + child.GetHashCode());
Debug.WriteLine("");
}
}
}
else // A timeout probably occured
{
return;
}
}
else
{
this.closedListHits++;
}
node.agentAExpansion = CbsNode.ExpansionState.EXPANDED;
}
// Generate right child:
int agentBGroupSize = node.GetGroupSize(node.agentsGroupAssignment[conflict.agentB]);
if (node.agentBExpansion == CbsNode.ExpansionState.NOT_EXPANDED && conflict.vertex == true &&
conflict.timeStep >= node.allSingleAgentCosts[conflict.agentB] &&
agentBGroupSize == 1) // Again, skip expansion
{
if (debug)
{
Debug.WriteLine("Skipping right child");
}
if (node.agentAExpansion == CbsNode.ExpansionState.DEFERRED)
{
throw new Exception("Unexpected: Expansion of both children differed, but this is a vertex conflict so that means the targets for the two agents are equal, which is illegal");
}
node.agentBExpansion = CbsNode.ExpansionState.DEFERRED;
int agentBOldCost = node.allSingleAgentCosts[conflict.agentB];
node.totalCost += (ushort)(conflict.timeStep + 1 - agentBOldCost);
openList.Add(node); // Re-insert node into open list with higher cost, don't re-increment global conflict counts
this.partialExpansions++;
// TODO: Code duplication with agentA. Make this into a function.
}
else if (node.agentBExpansion != CbsNode.ExpansionState.EXPANDED)
{
if (debug)
{
Debug.WriteLine("Generating right child");
}
var newConstraint = new CbsConstraint(conflict, instance, false);
child = new CbsNode(node, newConstraint, conflict.agentB);
if (closedList.ContainsKey(child) == false)
{
closedList.Add(child, child);
if (child.Replan(conflict.agentB, this.minDepth)) // The node takes the max between minDepth and the max time over all constraints.
{
if (child.totalCost < node.totalCost && node.agentAExpansion == CbsNode.ExpansionState.EXPANDED &&
agentBGroupSize == 1)
{
Debug.WriteLine("");
Debug.Write("Single agent costs: ");
for (int i = 0; i < child.allSingleAgentCosts.Length; i++)
{
Debug.Write(" " + child.allSingleAgentCosts[i]);
}
Debug.WriteLine("");
//Debug.WriteLine("Offending plan:");
//child.CalculateJointPlan().PrintPlan();
Debug.WriteLine("Chlid plan: (cost {0})", child.allSingleAgentCosts[conflict.agentB]);
child.allSingleAgentPlans[conflict.agentB].PrintPlan();
Debug.WriteLine("Parent plan: (cost {0})", node.allSingleAgentCosts[conflict.agentB]);
node.allSingleAgentPlans[conflict.agentB].PrintPlan();
Debug.Assert(false, "Single agent node with lower cost than parent! " + child.totalCost + " < " + node.totalCost);
}
if (child.totalCost <= this.maxCost)
{
openList.Add(child);
this.highLevelGenerated++;
addToGlobalConflictCount(child.GetConflict());
if (debug)
{
Debug.WriteLine("Child cost: " + child.totalCost);
Debug.WriteLine("Child hash: " + child.GetHashCode());
Debug.WriteLine("");
}
}
}
else // A timeout probably occured
{
return;
}
}
else
{
this.closedListHits++;
}
node.agentBExpansion = CbsNode.ExpansionState.EXPANDED;
}
}