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POMinimax for Connect Four (Unity3D and C#): Problems
 

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  1. POMinimax for Connect Four (Unity3D and C#): Problems
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    <p>I'm developing a Connect Four game with AI in Unity3D (C#). I use for this the MiniMax algorithm according to this (German) <a href="http://de.wikipedia.org/wiki/Minimax-Algorithmus" rel="nofollow">Pseudocode</a>.</p> <p>The AI is still playing pretty bad. It tries to get even 4 in a row, although there are only three free fields. The AI always goes through the row and blocks only when it is needed. Unfortunately, it also blocks not always.</p> <p><em><strong>Where to hide the problems? What have I forgotten?</em></strong></p> <p>How can I integrate random moves of the AI when no one wins or loses at the next move.</p> <p><strong>Here is my source code:</strong></p> <p>minimaxDepth = 4</p> <p>function call: Max (minimaxDepth, fieldCopy);</p> <pre><code>int Max (int depth, int[,] fieldCopy) { int maxValue = -9999; int moveValue; bool winAI = false; bool winHuman = false; bool isStoneBelow = false; for (int y = 0; y &lt; 6; y++) { for (int x = 0; x &lt; 7; x++) { if (y &gt; 0) { //is a stone under it? if (fieldCopy [x, y - 1] == 1 || fieldCopy [x, y - 1] == 2) { isStoneBelow = true; } else { isStoneBelow = false; } } else { isStoneBelow = true; } // possible move? if (fieldCopy [x, y] != 1 &amp;&amp; fieldCopy [x, y] != 2 &amp;&amp; isStoneBelow == true) { isStoneBelow = false; fieldCopy [x, y] = 2; //simulate move winAI = false; winHuman = false; //Is there a winner? if (CheckWin (x, y, 2, fieldCopy)) { winAI = true; winHuman = false; } //No more moves possible? if (depth &lt;= 1 || winAI == true) { moveValue = evaluationFunction (winAI, winHuman); //evaluate the move } else { moveValue = Min (depth - 1, fieldCopy); } fieldCopy [x, y] = 0; //Reset simulated move if (moveValue &gt; maxValue) { maxValue = moveValue; if (depth == minimaxDepth) { aiMoveX = x; // next move } } } } } return maxValue; } int Min (int depth, int[,] fieldCopy) { int minValue = 9999; int moveValue; bool winAI = false; bool winHuman = false; bool isStoneBelow = false; bool loopBreak = false; for (int y = 0; y &lt; 6; y++) { for (int x = 0; x &lt; 7; x++) { if (y &gt; 0) { //is a stone under it? if (fieldCopy [x, y - 1] == 1 || fieldCopy [x, y - 1] == 2) { isStoneBelow = true; } else { isStoneBelow = false; } } else { isStoneBelow = true; } // possible move? if (fieldCopy [x, y] != 1 &amp;&amp; fieldCopy [x, y] != 2 &amp;&amp; isStoneBelow == true) { isStoneBelow = false; fieldCopy [x, y] = 1; //simulate move winHuman = false; winAI = false; //Is there a winner? if (CheckWin (x, y, 1, fieldCopy)) { winHuman = true; winAI = false; } //No more moves possible? if (depth &lt;= 1 || winHuman == true) { moveValue = evaluationFunction (winAI, winHuman); //evaluate the move } else { moveValue = Max (depth - 1, fieldCopy); } fieldCopy [x, y] = 0; //Reset simulated move if (moveValue &lt; minValue) { minValue = moveValue; } } } } return minValue; } int evaluationFunction (bool winAI, bool winHuman) { if (winAI) { return 1; } else if (winHuman) { return -1; } else { return 0; } } </code></pre> <p>Thanks for your help!</p>
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      1. POMinimax for Connect Four (Unity3D and C#): Problems
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    1. COTL;DR. You're asking us to debug something but give it a try yourself first. Construct the path to the first move on paper and see where the actual code deviates.
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      1. POMinimax for Connect Four (Unity3D and C#): Problems
      1. USHenk Holterman
    2. COThe first question is a general question not a question to my source code and I debug my source code repeatedly. Due to the recursion, it is not so easy.
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      1. USOli
    3. CONo, debugging recursive code certainly isn't easy...but necessary in this case. Given the code, as it is written, you should be able to figure out EXACTLY what the AI's next move should be given any initial state you care to setup. Knowing that, and seeing what move it actually makes, will tell you a Lot. Your job is to figure out, not just why it isn't doing what it should, but why it IS doing whatever it's doing.
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      1. POMinimax for Connect Four (Unity3D and C#): Problems
      1. USNevyn
 

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