// Given a tree layer, creates the next layer of child nodes and returns them.
public static List <StateSpaceNode> BuildLayer(Planner planner, List <StateSpaceNode> currentLayer)
{
// Create a new list for the child nodes.
List <StateSpaceNode> childLayer = new List <StateSpaceNode>();
// Loop through the nodes in the current layer.
foreach (StateSpaceNode node in currentLayer)
{
// Loop through all outgoing edges of the current node.
foreach (StateSpaceEdge edge in node.outgoing)
{
// Generate the child node.
StateSpaceNode child = CreateChild(planner, node.domain, node.problem, node.plan, node.state, edge);
// Set the child's parent to this node.
child.parent = node;
// Add the child to the parent's collection of children, by way of the current action.
node.children[edge] = child;
// Add the node to the child layer
childLayer.Add(child);
}
}
// Return the child layer.
return(childLayer);
}
// Checks whether a node is a leaf or a branch.
public static Boolean CheckLeaf(Plan plan, State state, StateSpaceNode node)
{
// Return any empty plans.
if (plan.Steps.Count == 0)
{
// If the goal is satisfied...
if (state.Satisfies(plan.GoalStep.Preconditions))
{
// Differentiate a satisfied goal.
node.satisfiesGoal = true;
// Record that a goal state was reached.
StateSpaceMediator.GoalStateCount++;
}
else
{
// Record that a dead end state was reached.
StateSpaceMediator.DeadEndCount++;
}
// Return that the node is a leaf.
return(true);
}
// Return that the node is a branch.
return(false);
}
public StateSpaceNode(StateSpaceNode parent, StateSpaceEdge incoming, State state)
{
this.parent = parent;
this.incoming = incoming;
systemActions = new List <IOperator>();
this.state = state;
outgoing = new List <StateSpaceEdge>();
children = new Hashtable();
plan = new Plan();
problem = new Problem();
domain = new Domain();
id = System.Threading.Interlocked.Increment(ref Counter);
satisfiesGoal = false;
}
public StateSpaceNode()
{
parent = null;
incoming = null;
systemActions = new List <IOperator>();
state = new State();
outgoing = new List <StateSpaceEdge>();
children = new Hashtable();
plan = new Plan();
problem = new Problem();
domain = new Domain();
id = System.Threading.Interlocked.Increment(ref Counter);
satisfiesGoal = false;
}
// Creates and returns a new node.
public static StateSpaceNode CreateNode(Planner planner, Domain domain, Problem problem, Plan plan, State state)
{
// Create a node for the current state.
StateSpaceNode root = new StateSpaceNode();
// Record that a node was created.
StateSpaceMediator.NodeCount++;
// Check if the node is a leaf.
if (StateSpaceSearchTools.CheckLeaf(plan, state, root))
{
return(root);
}
// Set the node's domain.
root.domain = domain;
// Set the node's problem.
root.problem = problem;
// Set the node's plan.
root.plan = plan;
// Set the node's state.
root.state = state;
// Find out what the player knows.
root.problem.Initial = RobertsonMicrotheory.Annotate(problem.Initial, problem.Player);
// Find all outgoing user actions from this state.
root.outgoing = StateSpaceTools.GetAllPossibleActions(domain, problem, plan, state);
// Record the number of outgoing edges.
StateSpaceMediator.OutgoingEdgesCount = StateSpaceMediator.OutgoingEdgesCount + root.outgoing.Count;
// Return the current node.
return(root);
}
// Creates a child node.
private static StateSpaceNode CreateChild(Planner planner, Domain domain, Problem problem, Plan plan, State state, StateSpaceEdge edge)
{
// Create a new problem object.
Problem newProblem = new Problem();
// Create a new domain object.
Domain newDomain = domain;
// Create a new plan object.
Plan newPlan = new Plan();
// Store actions the system takes.
List <IOperator> systemActions = new List <IOperator>();
// If the outgoing action is an exceptional step...
if (edge.ActionType == ActionType.Exceptional)
{
// Count the exceptional edge.
Exceptional++;
// Create a new problem object.
newProblem = NewProblem(newDomain, problem, state, edge.Action);
// Find a new plan.
newPlan = PlannerInterface.Plan(planner, newDomain, newProblem);
// If the action was accommodated and the first step of the new plan isn't taken by the player...
if (newPlan.Steps.Count > 0)
{
// Add the action to the system action list.
systemActions = GetSystemActions(newPlan, new List <string> {
problem.Player
}, new List <IOperator>());
// Update the problem object with the system's next move.
newProblem = NewProblem(newDomain, newProblem, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()), systemActions);
// Update the plan with the system's next move.
newPlan = newPlan.GetPlanUpdate(newProblem, systemActions);
}
else if (CEDeletion)
{
// Try to find a domain revision alibi.
Tuple <Domain, Operator> alibi = ReviseDomain(planner, newDomain, problem, state, edge.Action as Operator);
// If domain revision worked.
if (alibi != null)
{
// Remember the new domain.
newDomain = alibi.First;
// Push the modified action to the edge object.
edge.Action = alibi.Second;
// Create a new problem object.
newProblem = NewProblem(newDomain, problem, state, edge.Action);
// Find a new plan.
newPlan = PlannerInterface.Plan(planner, newDomain, newProblem);
// Add the action to the system action list.
systemActions = GetSystemActions(newPlan, new List <string> {
problem.Player
}, new List <IOperator>());
// Update the problem object with the system's next move.
newProblem = NewProblem(newDomain, newProblem, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()), systemActions);
// Update the plan with the system's next move.
newPlan = newPlan.GetPlanUpdate(newProblem, systemActions);
}
}
}
// Otherwise, if the action is a consistent step...
else if (edge.ActionType == ActionType.Consistent)
{
// Count the consistent edge.
Consistent++;
// Create a new problem object.
newProblem = NewProblem(newDomain, problem, state, edge.Action);
// Add the action to the system action list.
systemActions = GetSystemActions(plan, new List <string> {
problem.Player
}, new List <IOperator>());
// Create a new state.
State newState = new State(newProblem.Initial, state.nextStep, (Operator)plan.Steps.First());
// Create a new problem object.
newProblem = NewProblem(newDomain, newProblem, newState, systemActions);
// Create a new plan.
newPlan = plan.GetPlanUpdate(newProblem, systemActions);
}
// Otherwise, the action is a constituent step...
else
{
// Count the constituent edge.
Constituent++;
// If there are effects of the constituent action...
if (edge.Action.Effects.Count > 0)
{
// Create a new problem object.
newProblem = NewProblem(newDomain, problem, state, edge.Action);
// Create a new plan.
newPlan = plan.GetPlanUpdate(newProblem, edge.Action as Operator);
}
// Otherwise, initialize to the old problem and plan...
else
{
newProblem = problem;
newPlan = plan.Clone() as Plan;
}
// If there are still plan actions...
if (newPlan.Steps.Count > 0)
{
// Add the action to the system action list.
systemActions = GetSystemActions(newPlan, new List <string> {
problem.Player
}, new List <IOperator>());
// Update the problem object with the system's next move.
newProblem = NewProblem(newDomain, newProblem, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()), systemActions);
// Update the plan with the system's next move.
newPlan = newPlan.GetPlanUpdate(newProblem, systemActions);
}
}
// Add the system actions to the current edge.
edge.SystemActions = systemActions;
// Create an empty child node.
StateSpaceNode child = null;
// If there are remaining plan steps...
if (newPlan.Steps.Count > 0)
{
// Build a new tree using the first step of the plan as the next step.
child = StateSpaceSearchTools.CreateNode(planner, newDomain, newProblem, newPlan, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()));
}
else
{
// Terminate the tree by adding a goal node.
child = StateSpaceSearchTools.CreateNode(planner, newDomain, newProblem, newPlan, new State(newProblem.Initial, newPlan.InitialStep, newPlan.GoalStep));
}
// Store the system actions.
child.systemActions = systemActions;
// Record the action that triggered the node's generation.
child.incoming = edge;
return(child);
}
// Expand an edge.
public static StateSpaceNode ExpandTree(Planner planner, Domain domain, Problem problem, Plan plan, State state, StateSpaceEdge edge, int depth)
{
// Create a new problem object.
Problem newProblem = new Problem();
// Create a new plan object.
Plan newPlan = new Plan();
// Store actions the system takes.
List <IOperator> systemActions = new List <IOperator>();
// If the action is an exceptional step...
if (edge.ActionType == ActionType.Exceptional)
{
// Count the exceptional edge.
Exceptional++;
// Create a new problem object.
newProblem = NewProblem(domain, problem, state, edge.Action);
// Find a new plan.
newPlan = PlannerInterface.Plan(planner, domain, newProblem);
// If the action was accommodated and the first step of the new plan isn't taken by the player...
if (newPlan.Steps.Count > 0)
{
// Add the action to the system action list.
systemActions = GetSystemActions(newPlan, new List <string> {
problem.Player
}, new List <IOperator>());
// Update the problem object with the system's next move.
newProblem = NewProblem(domain, newProblem, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()), systemActions);
// Update the plan with the system's next move.
newPlan = newPlan.GetPlanUpdate(newProblem, systemActions);
}
else if (CEDeletion)
{
StateSpaceNode alibi = GenerateAlibi(planner, domain, problem, plan, state, edge, depth);
if (alibi != null)
{
return(alibi);
}
}
}
// Otherwise, if the action is a consistent step...
else if (edge.ActionType == ActionType.Consistent)
{
// Count the consistent edge.
Consistent++;
// Create a new problem object.
newProblem = NewProblem(domain, problem, state, edge.Action);
// Add the action to the system action list.
systemActions = GetSystemActions(plan, new List <string> {
problem.Player
}, new List <IOperator>());
// Create a new state.
State newState = new State(newProblem.Initial, state.nextStep, (Operator)plan.Steps.First());
// Create a new problem object.
newProblem = NewProblem(domain, newProblem, newState, systemActions);
// Create a new plan.
newPlan = plan.GetPlanUpdate(newProblem, systemActions);
}
// Otherwise, the action is a constituent step...
else
{
// Count the constituent edge.
Constituent++;
// If there are effects of the constituent action...
if (edge.Action.Effects.Count > 0)
{
// Create a new problem object.
newProblem = NewProblem(domain, problem, state, edge.Action);
// Create a new plan.
newPlan = plan.GetPlanUpdate(newProblem, edge.Action as Operator);
}
// Otherwise, initialize to the old problem and plan...
else
{
newProblem = problem;
newPlan = plan.Clone() as Plan;
}
// If there are still plan actions...
if (newPlan.Steps.Count > 0)
{
// Add the action to the system action list.
systemActions = GetSystemActions(newPlan, new List <string> {
problem.Player
}, new List <IOperator>());
// Update the problem object with the system's next move.
newProblem = NewProblem(domain, newProblem, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()), systemActions);
// Update the plan with the system's next move.
newPlan = newPlan.GetPlanUpdate(newProblem, systemActions);
}
}
// Add the system actions to the current edge.
edge.SystemActions = systemActions;
// Create an empty child node.
StateSpaceNode child = null;
// If there are remaining plan steps...
if (newPlan.Steps.Count > 0)
{
// Build a new tree using the first step of the plan as the next step.
child = BuildTree(planner, domain, newProblem, newPlan, new State(newProblem.Initial, newPlan.InitialStep, (Operator)newPlan.Steps.First()), depth - 1);
}
else
{
// Terminate the tree by adding a goal node.
child = BuildTree(planner, domain, newProblem, newPlan, new State(newProblem.Initial, newPlan.InitialStep, newPlan.GoalStep), depth - 1);
}
// Store the system actions.
child.systemActions = systemActions;
// Record the action that triggered the node's generation.
child.incoming = edge;
return(child);
}
// Build the mediation tree using a depth-first strategy.
public static StateSpaceNode BuildTree(Planner planner, Domain domain, Problem problem, Plan plan, State state, int depth)
{
// Create a node for the current state.
StateSpaceNode root = new StateSpaceNode();
// Record that a node was created.
NodeCount++;
// Return any empty plans.
if (plan.Steps.Count == 0)
{
// If the goal is satisfied...
if (state.Satisfies(plan.GoalStep.Preconditions))
{
// Differentiate a satisfied goal.
root.satisfiesGoal = true;
// Record that a goal state was reached.
GoalStateCount++;
}
else
{
// Record that a dead end state was reached.
DeadEndCount++;
}
// Return the leaf node.
return(root);
}
// Set the node's domain.
root.domain = domain;
// Set the node's problem.
root.problem = problem;
// Set the node's plan.
root.plan = plan;
// Set the node's state.
root.state = state;
// Find out what the player knows.
root.problem.Initial = RobertsonMicrotheory.Annotate(problem.Initial, problem.Player);
// Find all outgoing user actions from this state.
root.outgoing = StateSpaceTools.GetAllPossibleActions(domain, problem, plan, state);
// Return the node if the depth limit has been reached.
if (depth <= 0)
{
return(root);
}
// Loop through the possible actions.
foreach (StateSpaceEdge edge in root.outgoing)
{
StateSpaceNode child = ExpandTree(planner, domain, problem, plan.Clone() as Plan, state.Clone() as State, edge, depth);
// Set the child's parent to this node.
child.parent = root;
// Add the child to the parent's collection of children, by way of the current action.
root.children[edge] = child;
}
// Return the current node.
return(root);
}
