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POWikipedia A* pathfinding algorithm takes a lot of time
 

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  1. POWikipedia A* pathfinding algorithm takes a lot of time
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    <p>I've successfully implemented A* pathfinding in C# but it is very slow, and I don't understand why. I even tried not sorting the openNodes list but it's still the same.</p> <p>The map is 80x80, and there are 10-11 nodes.</p> <p>I took the pseudocode from here <a href="http://en.wikipedia.org/wiki/A%2a_search_algorithm#Pseudocode" rel="nofollow">Wikipedia</a></p> <p>And this is my implementation:</p> <pre><code> public static List&lt;PGNode&gt; Pathfind(PGMap mMap, PGNode mStart, PGNode mEnd) { mMap.ClearNodes(); mMap.GetTile(mStart.X, mStart.Y).Value = 0; mMap.GetTile(mEnd.X, mEnd.Y).Value = 0; List&lt;PGNode&gt; openNodes = new List&lt;PGNode&gt;(); List&lt;PGNode&gt; closedNodes = new List&lt;PGNode&gt;(); List&lt;PGNode&gt; solutionNodes = new List&lt;PGNode&gt;(); mStart.G = 0; mStart.H = GetManhattanHeuristic(mStart, mEnd); solutionNodes.Add(mStart); solutionNodes.Add(mEnd); openNodes.Add(mStart); // 1) Add the starting square (or node) to the open list. while (openNodes.Count &gt; 0) // 2) Repeat the following: { openNodes.Sort((p1, p2) =&gt; p1.F.CompareTo(p2.F)); PGNode current = openNodes[0]; // a) We refer to this as the current square.) if (current == mEnd) { while (current != null) { solutionNodes.Add(current); current = current.Parent; } return solutionNodes; } openNodes.Remove(current); closedNodes.Add(current); // b) Switch it to the closed list. List&lt;PGNode&gt; neighborNodes = current.GetNeighborNodes(); double cost = 0; bool isCostBetter = false; for (int i = 0; i &lt; neighborNodes.Count; i++) { PGNode neighbor = neighborNodes[i]; cost = current.G + 10; isCostBetter = false; if (neighbor.Passable == false || closedNodes.Contains(neighbor)) continue; // If it is not walkable or if it is on the closed list, ignore it. if (openNodes.Contains(neighbor) == false) { openNodes.Add(neighbor); // If it isn’t on the open list, add it to the open list. isCostBetter = true; } else if (cost &lt; neighbor.G) { isCostBetter = true; } if (isCostBetter) { neighbor.Parent = current; // Make the current square the parent of this square. neighbor.G = cost; neighbor.H = GetManhattanHeuristic(current, neighbor); } } } return null; } </code></pre> <p>Here's the heuristic I'm using:</p> <pre><code> private static double GetManhattanHeuristic(PGNode mStart, PGNode mEnd) { return Math.Abs(mStart.X - mEnd.X) + Math.Abs(mStart.Y - mEnd.Y); } </code></pre> <p>What am I doing wrong? It's an entire day I keep looking at the same code.</p>
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    1. USVittorio Romeo
    1. USVittorio Romeo
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      1. POWikipedia A* pathfinding algorithm takes a lot of time
      1. USChristopher Klein
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    1. COWhat is the size of your map? The number of expansions depends on the distance to the target node, and that depends on the map size.
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      1. POWikipedia A* pathfinding algorithm takes a lot of time
      1. USRodrigo Hahn
    2. COHow many nodes do you have in the list? What exactly is "slow" - how long it takes to do something?
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    3. COThe map is 80x80.
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      1. USVittorio Romeo
 

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