/// <summary>
/// Returns all the children of a given MDD node that have a heuristic estimate that is not larger than the given heuristic bound.
/// </summary>
/// <param name="mdd"></param>
/// <param name="heuristicBound">The heuristic estimate of the returned children must be lower than or equal to the bound</param>
/// <param name="numOfAgents">The number of agents in the MDD node</param>
/// <returns>A list of relevant MDD nodes</returns>
private List <MDDNode> GetAllChildren(MDDNode father, int heuristicBound, int numOfAgents)
{
var children = new List <MDDNode>();
foreach (TimedMove move in father.move.GetNextMoves())
{
if (this.problem.IsValid(move) &&
this.problem.GetSingleAgentOptimalCost(this.agentNum, move) <= heuristicBound) // Only nodes that can reach the goal in the given cost according to the heuristic.
{
if (this.constraints != null)
{
queryConstraint.Init(agentNum, move);
if (this.constraints.Contains(queryConstraint))
{
continue;
}
}
if (this.mustConstraints != null && move.time < this.mustConstraints.Length && // There may be a constraint on the timestep of the generated node
this.mustConstraints[move.time] != null &&
this.mustConstraints[move.time].ContainsKey(this.agentNum)) // This agent has a must constraint for this time step
{
if (this.mustConstraints[move.time][this.agentNum].Equals(move) == false)
{
continue;
}
}
MDDNode child = new MDDNode(move, numOfAgents, this, this.supportPruning);
children.Add(child);
}
}
return(children);
}
/// <summary>
/// Check if the move is valid, i.e. not colliding into walls or other agents.
/// This method is here instead of in ProblemInstance to enable algorithmic tweaks.
/// </summary>
/// <param name="possibleMove">The move to check if possible</param>
/// <returns>true, if the move is possible.</returns>
protected bool IsValid(TimedMove possibleMove, HashSet <TimedMove> currentMoves, int makespan, int agentNum)
{
// Check if the proposed move is reserved in the plan of another agent.
// This is used in Trevor's IndependenceDetection.
if (this.illegalMoves != null)
{
if (possibleMove.IsColliding(illegalMoves))
{
return(false);
}
} // FIXME: Also checked in instance.IsValid later.
if (this.constraintList != null)
{
queryConstraint.Init(agentNum, possibleMove);
if (this.constraintList.Contains(queryConstraint))
{
return(false);
}
}
if (this.mustConstraints != null && makespan < this.mustConstraints.Length && // There may be a constraint on the timestep of the generated node
this.mustConstraints[makespan] != null)
{
if (this.mustConstraints[makespan].Any <CbsConstraint>(
con => con.ViolatesMustConstraint((byte)agentNum, possibleMove)))
{
return(false);
}
}
// If the tile is not free (out of the grid or with an obstacle)
if (this.instance.IsValid(possibleMove) == false)
{
return(false);
}
// Check against all the agents that have already moved to see if current move collides with their move
return(possibleMove.IsColliding(currentMoves) == false);
}