// generate the children of state 'node'
// state is the GameState after node's moves have been performed
void UCTSearch::generateChildren(UCTNode & node, GameState & state)
{
// figure out who is next to move in the game
const IDType playerToMove(getPlayerToMove(node, state));
// generate all the moves possible from this state
state.generateMoves(_moveArray, playerToMove);
_moveArray.shuffleMoveActions();
// generate the 'ordered moves' for move ordering
generateOrderedMoves(state, _moveArray, playerToMove);
// for each child of this state, add a child to the current node
for (size_t child(0); (child < _params.maxChildren()) && getNextMove(playerToMove, _moveArray, child, _actionVec); ++child)
{
// add the child to the tree
node.addChild(&node, playerToMove, getChildNodeType(node, state), _actionVec, _params.maxChildren(), _memoryPool ? _memoryPool->alloc() : NULL);
_results.nodesCreated++;
}
}
AlphaBetaValue AlphaBeta::alphaBeta(GameState & state, size_t depth, const IDType lastPlayerToMove, const MoveTuple * prevSimMove, AlphaBetaScore alpha, AlphaBetaScore beta)
{
// update statistics
_results.nodesExpanded++;
if (searchTimeOut())
{
throw 1;
}
if (terminalState(state, depth))
{
// return the value, but the move will not be valid since none was performed
AlphaBetaScore evalScore = state.eval(_params.maxPlayer(), _params.evalMethod(), _params.modelSimMethod());
return AlphaBetaValue(AlphaBetaScore(evalScore.val(), state.getNumMovements(_params.maxPlayer()) + evalScore.numMoves() ), AlphaBetaMove(0, false));
}
// figure out which player is to move
const IDType playerToMove(getPlayerToMove(state, depth, lastPlayerToMove, !prevSimMove));
// is the player to move the max player?
bool maxPlayer = (playerToMove == _params.maxPlayer());
// Transposition Table Logic
TTLookupValue TTval;
if (isTranspositionLookupState(state, prevSimMove))
{
TTval = TTlookup(state, alpha, beta, depth);
// if this is a TT cut, return the proper value
if (TTval.cut())
{
return AlphaBetaValue(TTval.entry()->getScore(), getAlphaBetaMove(TTval, playerToMove));
}
}
bool bestMoveSet(false);
// move generation
MoveArray & moves = _allMoves[depth];
state.generateMoves(moves, playerToMove);
generateOrderedMoves(state, moves, TTval, playerToMove, depth);
// while we have more simultaneous move tuples
AlphaBetaMove bestMove, bestSimResponse;
MoveTuple numMoveTuples(getNumMoveTuples(moves, TTval, playerToMove, depth));
for (MoveTuple t(0); t < numMoveTuples; ++t)
{
// get the tuple that will be implemented
const MoveTuple tuple = getNextMoveTuple(t, depth);
// the value of the recursive AB we will call
AlphaBetaValue val;
// generate the child state
GameState child(state);
bool firstMove = true;
// if this is the first player in a simultaneous move state
if (state.bothCanMove() && !prevSimMove && (depth != 1))
{
firstMove = true;
// don't generate a child yet, just pass on the move we are investigating
val = alphaBeta(state, depth-1, playerToMove, &tuple, alpha, beta);
}
else
{
firstMove = false;
// if this is the 2nd move of a simultaneous move state
if (prevSimMove)
{
// do the previous move tuple selected by the first player to move during this state
doTupleMoves(child, _allMoves[depth+1], *prevSimMove);
}
// do the moves of the current player
doTupleMoves(child, moves, tuple);
child.finishedMoving(true);
// get the alpha beta value
val = alphaBeta(child, depth-1, playerToMove, NULL, alpha, beta);
}
// set alpha or beta based on maxplayer
if (maxPlayer && (val.score() > alpha))
{
alpha = val.score();
bestMove = AlphaBetaMove(tuple, true);
bestMoveSet = true;
if (state.bothCanMove() && !prevSimMove)
{
bestSimResponse = val.abMove();
}
// if this is depth 1 of the first try at depth 1, store the best in results
}
else if (!maxPlayer && (val.score() < beta))
{
beta = val.score();
bestMove = AlphaBetaMove(tuple, true);
bestMoveSet = true;
if (state.bothCanMove() && prevSimMove)
{
bestSimResponse = val.abMove();
}
}
if (alpha.val() == -10000000 && beta.val() == 10000000)
{
fprintf(stderr, "\n\nALPHA BETA ERROR, NO VALUE SET\n\n");
}
// alpha-beta cut
if (alpha >= beta)
{
break;
}
}
if (isTranspositionLookupState(state, prevSimMove))
{
TTsave(state, maxPlayer ? alpha : beta, alpha, beta, depth, playerToMove, bestMove, bestSimResponse);
}
return maxPlayer ? AlphaBetaValue(alpha, bestMove) : AlphaBetaValue(beta, bestMove);
}
void AlphaBeta::generateOrderedMoves(GameState & state, MoveArray & moves, const TTLookupValue & TTval, const IDType & playerToMove, const size_t & depth)
{
// get the array where we will store the moves and clear it
Array<MoveTuple, Search::Constants::Max_Ordered_Moves> & orderedMoves(_orderedMoves[depth]);
orderedMoves.clear();
// if we are using opponent modeling, get the move and then return, we don't want to put any more moves in
if (_params.usePlayerModel(playerToMove))
{
MoveTuple playerModelMove = _params.getPlayer(playerToMove)->getMoveTuple(state, moves);
orderedMoves.add(playerModelMove);
return;
}
// if there is a transposition table entry for this state
if (TTval.found())
{
// get the abMove we stored for this player
const AlphaBetaMove & abMove = getAlphaBetaMove(TTval, playerToMove);
// here we get an incorrect move from the transposition table
if (abMove.moveTuple() >= moves.numMoveTuples())
{
HashType h0 = state.calculateHash(0);
HashType h1 = state.calculateHash(1);
MoveArray moves2;
state.generateMoves(moves2, playerToMove);
// figure out why
//fprintf(stderr, "Something very wrong, this tuple (%d) doesn't exist, only (%d) moves\n", (int)abMove.moveTuple(), (int)moves.numMoveTuples());
}
_results.ttFoundCheck++;
// Two checks:
// 1) Is the move 'valid' ie: was it actually set inside the TT
// 2) Is it a valid tuple number for this move set? This guards against double
// hash collision errors. Even if it is a collision, this is just a move
// ordering, so no errors should occur.
if (abMove.isValid() && (abMove.moveTuple() < moves.numMoveTuples()))
{
orderedMoves.add(abMove.moveTuple());
_results.ttMoveOrders++;
return;
}
else
{
_results.ttFoundButNoMove++;
}
}
// if we are using script modeling, insert the script moves we want
if (_params.useScriptMoveFirst())
{
for (size_t s(0); s<_allScripts.size(); s++)
{
MoveTuple scriptMove = _allScripts[s]->getMoveTuple(state, moves);
orderedMoves.addUnique(scriptMove);
}
}
}