Kalah AI

Question

Hi people,
my assignment is to create a simple AI for the game kalah (also known as mancala). this AI composed of making a min/max 'tree' (the tree is never created in the memory) it is all done by recursion. the game will send my AI class a gamestate, and then the AI will apply moves to this game state and keep doing this until the tree gets to depth d, where it will return a value that ranks the gamestate. it will return several values, so i just search for the max and then return that one. ultimately, the AI returns which position (pit on the board) to take the beans from, should be the the one that returned the highest rank.
here is my horrendous and ugly code...
// Roarke Randall
// 10.24.08
// CSE 23
// end of the game project #2
public class KalahAI73833446 implements KalahAI
     Position[] positions;
     int[] evaluations;
     GameState clone;
     GameState clone2;
     Boolean player;
     static final int DEPTH = 4;
     int maxevaluation;
     public Position chooseMove(GameState state)
          //System.out.println("choosing a move");
          player = false;
          clone = (GameState)state.clone();
          clone2 = (GameState)state.clone();
          positions = new Position[clone.getHolesPerPlayer()+1];
          evaluations = new int[clone.getHolesPerPlayer()+1];
          maxevaluation = 0;
          Position bestPos = null;
          if(clone.isTopPlayerTurn()) player = true;
          for(int i = 1; i <= clone.getHolesPerPlayer(); i++)
               try
                    clone.checkValidMove(clone.createPosition(player, i));
                    positions[i] = clone.createPosition( player, i);               
               }catch(InvalidMoveException e){
                    positions[i] = null;
          for( int i = 1; i <= clone.getHolesPerPlayer(); i++)
               clone = (GameState)state.clone();
               if(positions[i] != null)
                    try
                         clone.applyMove(clone.createPosition(
                                   clone.isTopPlayerTurn(), positions.getHoleNumber()));
                         evaluations[i] = search( clone, DEPTH);
                         if(evaluations[i] >= maxevaluation)
                              //System.out.println(evaluations[i]);
                              maxevaluation = evaluations[i];
                              bestPos = positions[i];
                    }catch(InvalidMoveException e){
                         //System.out.println("not a valid place");
                         evaluations[i] = -1;
          if( bestPos == null)
               for(int i = 1; i < state.getHolesPerPlayer()+1; i++)
                    try{
                         //System.out.println("something got fucked up");
                         clone.checkValidMove(clone.createPosition(clone.isTopPlayerTurn(), i));
                         bestPos = clone.createPosition(clone.isTopPlayerTurn(), i);
                    }catch (Exception e){}
          return state.createPosition(player, bestPos.getHoleNumber());
     public int search(GameState g, int depth)
          GameState gprime;
          int[] validpositions = new int[g.getHolesPerPlayer()+1];
          int[] evaluations2 = new int[g.getHolesPerPlayer()+1];
          int maxevaluation2 = 0;
          // leaf of the 'tree'
          if(depth == 0 )
               //System.out.println(evaluate(g));
               return evaluate(g);
          else
               validpositions = validPositions(g);
               // this computer's 'virtual' turn
               if( g.isTopPlayerTurn() && player
                    || !g.isTopPlayerTurn() && !player)
                    for(int i = 1; i < g.getHolesPerPlayer()+1; i++)
                         if(validpositions[i] != 0 )
                              gprime = (GameState) g.clone();
                              try
                                   gprime.applyMove(
                                             gprime.createPosition(gprime.isTopPlayerTurn(), i));
                                   evaluations2[i] = search(gprime, depth-1);
                                   if(evaluations2[i] > maxevaluation2)
                                        maxevaluation2 = evaluations2[i];
                              }catch(InvalidMoveException e)
                                   System.out.println("some how this 'valid position' wasnt valid");
                    //System.out.println(maxevaluation2);
                    return maxevaluation2;
               else // opponent 'virtual' turn
                    validpositions = validPositions(g);
                    int minevaluation2 = 0;
                    for(int i = 1; i < g.getHolesPerPlayer()+1; i++)
                         if(validpositions[i] != 0 )
                              gprime = (GameState) g.clone();
                              try
                                   gprime.applyMove(
                                             gprime.createPosition(gprime.isTopPlayerTurn(), i));
                                   evaluations2[i] = search(gprime, depth-1);
                                   if(evaluations2[i] < minevaluation2)
                                        minevaluation2 = evaluations2[i];
                              }catch(InvalidMoveException e)
                                   System.out.println("some how this 'valid position' wasnt valid");
                    return minevaluation2;
     public int evaluate( GameState g)
          return g.getBeanCount(g.createPosition(player, Position.POT)) -
               g.getBeanCount(g.createPosition(!player, Position.POT));
     public int[] validPositions(GameState g)
          int[] pos = new int[g.getHolesPerPlayer()+1];
          for(int i = 1; i < g.getHolesPerPlayer()+1; i++)
               try
                    g.checkValidMove(g.createPosition(g.isTopPlayerTurn(), i));
                    pos[i] = i;
               }catch (InvalidMoveException e)
                    pos[i] = 0;
          return pos;
http://www.ics.uci.edu/~goodrich/teach/ics23/LabManual/EndOfTheGame/ thats the project.
my problem is that some reason my search(...) returns 0, even though if i print the value that is supposed to be returned, it isnt 0. can anyone see something in here that would make that happen? please ask questions, i know my code is ugly and hard to follow probably.

Answer 1

// Roarke Randall
// 10.24.08
// CSE 23
// end of the game project #2
public class KalahAI73833446 implements KalahAI
     Position[] positions;
     int[] evaluations;
     GameState clone;
     GameState clone2;
     Boolean player;
     static final int DEPTH = 4;
     int maxevaluation;
     public Position chooseMove(GameState state)
          //System.out.println("choosing a move");
          player = false;
          clone = (GameState)state.clone();
          clone2 = (GameState)state.clone();
          positions = new Position[clone.getHolesPerPlayer()+1];
          evaluations = new int[clone.getHolesPerPlayer()+1];
          maxevaluation = 0;
          Position bestPos = null;
          if(clone.isTopPlayerTurn()) player = true;
          for(int i = 1; i <= clone.getHolesPerPlayer(); i++)
               try
                    clone.checkValidMove(clone.createPosition(player, i));
                    positions[i] = clone.createPosition( player, i);               
               }catch(InvalidMoveException e){
                    positions[i] = null;
          for( int i = 1; i <= clone.getHolesPerPlayer(); i++)
               clone = (GameState)state.clone();
               if(positions[i] != null)
                    try
                         clone.applyMove(clone.createPosition(
                                   clone.isTopPlayerTurn(), positions.getHoleNumber()));
                         evaluations[i] = search( clone, DEPTH);
                         if(evaluations[i] >= maxevaluation)
                              //System.out.println(evaluations[i]);
                              maxevaluation = evaluations[i];
                              bestPos = positions[i];
                    }catch(InvalidMoveException e){
                         //System.out.println("not a valid place");
                         evaluations[i] = -1;
          if( bestPos == null)
               for(int i = 1; i < state.getHolesPerPlayer()+1; i++)
                    try{
                         //System.out.println("something got fucked up");
                         clone.checkValidMove(clone.createPosition(clone.isTopPlayerTurn(), i));
                         bestPos = clone.createPosition(clone.isTopPlayerTurn(), i);
                    }catch (Exception e){}
          return state.createPosition(player, bestPos.getHoleNumber());
     public int search(GameState g, int depth)
          GameState gprime;
          int[] validpositions = new int[g.getHolesPerPlayer()+1];
          int[] evaluations2 = new int[g.getHolesPerPlayer()+1];
          int maxevaluation2 = 0;
          // leaf of the 'tree'
          if(depth == 0 )
               //System.out.println(evaluate(g));
               return evaluate(g);
          else
               validpositions = validPositions(g);
               // this computer's 'virtual' turn
               if( g.isTopPlayerTurn() && player
                    || !g.isTopPlayerTurn() && !player)
                    for(int i = 1; i < g.getHolesPerPlayer()+1; i++)
                         if(validpositions[i] != 0 )
                              gprime = (GameState) g.clone();
                              try
                                   gprime.applyMove(
                                             gprime.createPosition(gprime.isTopPlayerTurn(), i));
                                   evaluations2[i] = search(gprime, depth-1);
                                   if(evaluations2[i] > maxevaluation2)
                                        maxevaluation2 = evaluations2[i];
                              }catch(InvalidMoveException e)
                                   System.out.println("some how this 'valid position' wasnt valid");
                    //System.out.println(maxevaluation2);
                    return maxevaluation2;
               else // opponent 'virtual' turn
                    validpositions = validPositions(g);
                    int minevaluation2 = 0;
                    for(int i = 1; i < g.getHolesPerPlayer()+1; i++)
                         if(validpositions[i] != 0 )
                              gprime = (GameState) g.clone();
                              try
                                   gprime.applyMove(
                                             gprime.createPosition(gprime.isTopPlayerTurn(), i));
                                   evaluations2[i] = search(gprime, depth-1);
                                   if(evaluations2[i] < minevaluation2)
                                        minevaluation2 = evaluations2[i];
                              }catch(InvalidMoveException e)
                                   System.out.println("some how this 'valid position' wasnt valid");
                    return minevaluation2;
     public int evaluate( GameState g)
          return g.getBeanCount(g.createPosition(player, Position.POT)) -
               g.getBeanCount(g.createPosition(!player, Position.POT));
     public int[] validPositions(GameState g)
          int[] pos = new int[g.getHolesPerPlayer()+1];
          for(int i = 1; i < g.getHolesPerPlayer()+1; i++)
               try
                    g.checkValidMove(g.createPosition(g.isTopPlayerTurn(), i));
                    pos[i] = i;
               }catch (InvalidMoveException e)
                    pos[i] = 0;
          return pos;