Add Iterative Deepening search infrastructure
This commit is contained in:
Lucas Scharenbroich
parent
780f94050e
commit
2d25c5c295
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@ -25,7 +25,7 @@
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this.expander = expander;
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}
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public INodeExpander<A, S, T, C> Expander { get { return expander; } }
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public INodeExpander<A, S, T, C> Expander { get { return expander; } set { expander = value; } }
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public IEnumerable<T> Solution(T node)
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{
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@ -0,0 +1,24 @@
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namespace SpriteCompiler.AI
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{
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/// <summary>
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/// Class that taken a search node and detemines whether or not to terminate the
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/// search at the node. This is different than a goal test and is used in the
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/// contect of depth-limited searches.
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/// </summary>
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public class CostNodeLimiter<T, C> : INodeLimiter<T, C>
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where T : ISearchNode<C>
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where C : IPathCost<C>, new()
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{
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private readonly C maxCost;
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public CostNodeLimiter(C maxCost)
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{
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this.maxCost = maxCost;
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}
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public bool Cutoff(T node)
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{
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return node.PathCost.CompareTo(maxCost) >= 0;
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}
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}
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}
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@ -0,0 +1,32 @@
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace SpriteCompiler.AI
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{
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public class DepthFirstSearch<A, S, T, C> : ISearch<A, S, T, C>
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where T : ISearchNode<A, S, T, C>
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where C : IPathCost<C>, new()
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{
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protected readonly AbstractAISearch<A, S, T, C> search;
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protected readonly IQueue<T> fringe = new Lifo<T>();
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public DepthFirstSearch(AbstractAISearch<A, S, T, C> search)
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{
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this.search = search;
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}
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public virtual IEnumerable<T> Search(ISearchProblem<A, S, C> problem, S initialState)
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{
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fringe.Clear();
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return search.Search(problem, fringe, initialState);
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}
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public virtual IEnumerable<T> ExtendSearch(ISearchProblem<A, S, C> problem)
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{
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return search.ExtendSearch(problem, fringe);
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}
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}
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}
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@ -0,0 +1,35 @@
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace SpriteCompiler.AI
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{
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public class DepthLimitedNodeExpander<A, S, T, C> : NodeExpanderDelegator<A, S, T, C>
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where T : ISearchNode<A, S, T, C>
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where C : IPathCost<C>, new()
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{
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private readonly INodeLimiter<T, C> limit;
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private bool cutoffOccured = false;
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public DepthLimitedNodeExpander(INodeExpander<A, S, T, C> expander, INodeLimiter<T, C> limit)
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: base(expander)
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{
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this.limit = limit;
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}
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public bool CutoffOccured { get { return cutoffOccured; } }
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public override IEnumerable<T> Expand(ISearchProblem<A, S, C> problem, T node)
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{
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if (limit.Cutoff(node))
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{
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cutoffOccured = true;
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return Enumerable.Empty<T>();
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}
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return base.Expand(problem, node);
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}
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}
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}
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@ -0,0 +1,60 @@
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace SpriteCompiler.AI
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{
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/// <summary>
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/// Depth-first search with a cutoff
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/// </summary>
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public class DepthLimitedSearch<A, S, T, C> : DepthFirstSearch<A, S, T, C>
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where T : ISearchNode<A, S, T, C>
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where C : IPathCost<C>, new()
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{
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protected readonly INodeLimiter<T, C> limit;
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public DepthLimitedSearch(AbstractAISearch<A, S, T, C> search, INodeLimiter<T, C> limit)
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: base(search)
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{
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this.limit = limit;
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}
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public override IEnumerable<T> Search(ISearchProblem<A, S, C> problem, S initialState)
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{
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// Save the old node expander
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var oldExpander = search.Expander;
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// Wrap the expander with a depth-limied expanded in order to
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// terminate the search
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var expander = new DepthLimitedNodeExpander<A, S, T, C>(oldExpander, limit);
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search.Expander = expander;
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// Run the search
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var solution = base.Search(problem, initialState);
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// Restore the old expander
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search.Expander = oldExpander;
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// Check to see we failed and if the reason for failing was not reaching the cutoff depth.
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if (search.IsFailure(solution) && expander.CutoffOccured)
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{
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return null;
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}
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return solution;
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}
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public override IEnumerable<T> ExtendSearch(ISearchProblem<A, S, C> problem)
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{
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return base.ExtendSearch(problem);
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}
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public bool IsCutoff(IEnumerable<T> result)
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{
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return result == null;
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}
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}
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}
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@ -0,0 +1,9 @@
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namespace SpriteCompiler.AI
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{
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public interface INodeLimiter<T, C>
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where T : ISearchNode<C>
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where C : IPathCost<C>, new()
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{
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bool Cutoff(T node);
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}
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}
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@ -12,15 +12,15 @@
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public interface ISearchNode<A, S, T, C> : ISearchNode<C> where C : IPathCost<C>
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{
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A Action { get; set; }
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C PathCost { get; }
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C StepCost { get; set; }
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int Depth { get; }
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S State { get; }
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T Parent { get; }
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}
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public interface ISearchNode<C>
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{
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C PathCost { get; }
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C StepCost { get; set; }
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int Depth { get; }
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C EstCost { get; }
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}
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}
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@ -0,0 +1,45 @@
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace SpriteCompiler.AI
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{
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public class IterativeDeepeningAStarSearch<A, S, T, C> : ISearch<A, S, T, C>
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where T : ISearchNode<A, S, T, C>
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where C : IPathCost<C>, new()
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{
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protected readonly AbstractAISearch<A, S, T, C> search;
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protected readonly C limit;
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public IterativeDeepeningAStarSearch(AbstractAISearch<A, S, T, C> search, C limit)
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{
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this.search = search;
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this.limit = limit;
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}
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public IEnumerable<T> Search(ISearchProblem<A, S, C> problem, S initialState)
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{
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C bound = new C();
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while (bound.CompareTo(limit) < 0)
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{
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var dls = new DepthLimitedSearch<A, S, T, C>(search, new CostNodeLimiter<T, C>(bound));
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var result = dls.Search(problem, initialState);
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if (!dls.IsCutoff(result))
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{
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return result;
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}
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}
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// An empty list signals failure
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return Enumerable.Empty<T>();
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}
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public IEnumerable<T> ExtendSearch(ISearchProblem<A, S, C> problem)
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{
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throw new NotImplementedException();
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}
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}
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}
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@ -0,0 +1,41 @@
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace SpriteCompiler.AI
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{
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public class Lifo<T> : IQueue<T>
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{
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private readonly Stack<T> stack = new Stack<T>();
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public void Clear()
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{
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stack.Clear();
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}
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public bool Empty
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{
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get { return stack.Count == 0; }
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}
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public T Remove()
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{
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return stack.Pop();
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}
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public void Enqueue(T item)
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{
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stack.Push(item);
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}
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public void AddRange(IEnumerable<T> items)
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{
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foreach (var item in items)
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{
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stack.Push(item);
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}
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}
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}
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}
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@ -0,0 +1,26 @@
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namespace SpriteCompiler.AI
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{
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using System.Collections.Generic;
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public class NodeExpanderDelegator<A, S, T, C> : INodeExpander<A, S, T, C>
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where T : ISearchNode<A, S, T, C>
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where C : IPathCost<C>
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{
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private readonly INodeExpander<A, S, T, C> expander;
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public NodeExpanderDelegator(INodeExpander<A, S, T, C> expander)
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{
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this.expander = expander;
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}
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public virtual IEnumerable<T> Expand(ISearchProblem<A, S, C> problem, T node)
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{
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return expander.Expand(problem, node);
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}
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public virtual T CreateNode(T parent, S state)
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{
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return expander.CreateNode(parent, state);
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}
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}
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}
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@ -58,9 +58,14 @@
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<Compile Include="AI\AStarComparer.cs" />
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<Compile Include="AI\AStarSearch.cs" />
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<Compile Include="AI\BestFirstSearch.cs" />
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<Compile Include="AI\CostNodeLimiter.cs" />
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<Compile Include="AI\DepthFirstSearch.cs" />
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<Compile Include="AI\DepthLimitedNodeExpander.cs" />
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<Compile Include="AI\DepthLimitedSearch.cs" />
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<Compile Include="AI\HeuristicSearchNode.cs" />
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<Compile Include="AI\IHeuristicFunction.cs" />
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<Compile Include="AI\InformedNodeExpander.cs" />
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<Compile Include="AI\INodeLimiter.cs" />
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<Compile Include="AI\ISuccessorFunction.cs" />
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<Compile Include="AI\IGoalTest.cs" />
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<Compile Include="AI\INodeExpander.cs" />
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@ -70,6 +75,9 @@
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<Compile Include="AI\ISearchNode.cs" />
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<Compile Include="AI\ISearchProblem.cs" />
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<Compile Include="AI\IStepCostFunction.cs" />
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<Compile Include="AI\IterativeDeepeningAStarSearch.cs" />
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<Compile Include="AI\Lifo.cs" />
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<Compile Include="AI\NodeExpanderDelegator.cs" />
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<Compile Include="AI\SearchProblem.cs" />
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<Compile Include="AI\GraphSearch.cs" />
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<Compile Include="AI\TreeSearch.cs" />
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