/// Local functions
Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
- Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
template <NodeType PvNode, bool SpNode, bool Root>
Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
/// think() is the external interface to Stockfish's search, and is called when
/// the program receives the UCI 'go' command. It initializes various
-/// search-related global variables, and calls root_search(). It returns false
+/// search-related global variables, and calls id_loop(). It returns false
/// when a quit command is received during the search.
bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
namespace {
- // id_loop() is the main iterative deepening loop. It calls root_search
+ // id_loop() is the main iterative deepening loop. It calls search()
// repeatedly with increasing depth until the allocated thinking time has
// been consumed, the user stops the search, or the maximum search depth is
// reached.
rml.sort();
// Search to the current depth, rml is updated and sorted
- //value = root_search(pos, ss, alpha, beta, depth, rml);
value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
// Sort the moves before to return
}
- // root_search() is the function which searches the root node. It is
- // similar to search_pv except that it prints some information to the
- // standard output and handles the fail low/high loops.
-
- Value root_search(Position& pos, SearchStack* ss, Value alpha,
- Value beta, Depth depth, RootMoveList& rml) {
-
- assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
- assert(beta > alpha && beta <= VALUE_INFINITE);
- assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
-
- Move movesSearched[MOVES_MAX];
- StateInfo st;
- Key posKey;
- Move move;
- Depth ext, newDepth;
- ValueType vt;
- Value bestValue, value, oldAlpha;
- bool isCheck, moveIsCheck, captureOrPromotion, dangerous, isPvMove;
- int moveCount = 0;
-
- bestValue = value = -VALUE_INFINITE;
- oldAlpha = alpha;
- isCheck = pos.is_check();
-
- // Step 1. Initialize node (polling is omitted at root)
- ss->currentMove = ss->bestMove = MOVE_NONE;
- (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
-
- // Step 2. Check for aborted search (omitted at root)
- // Step 3. Mate distance pruning (omitted at root)
- // Step 4. Transposition table lookup (omitted at root)
- posKey = pos.get_key();
-
- // Step 5. Evaluate the position statically
- // At root we do this only to get reference value for child nodes
- ss->evalMargin = VALUE_NONE;
- ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
-
- // Step 6. Razoring (omitted at root)
- // Step 7. Static null move pruning (omitted at root)
- // Step 8. Null move search with verification search (omitted at root)
- // Step 9. Internal iterative deepening (omitted at root)
-
- CheckInfo ci(pos);
- int64_t nodes;
- RootMoveList::iterator rm = rml.begin();
- bestValue = alpha;
-
- // Step 10. Loop through moves
- // Loop through all legal moves until no moves remain or a beta cutoff occurs
- while ( bestValue < beta
- && rm != rml.end()
- && !StopRequest)
- {
- move = ss->currentMove = rm->pv[0];
- movesSearched[moveCount++] = move;
- isPvMove = (moveCount <= MultiPV);
-
- // This is used by time management
- FirstRootMove = (rm == rml.begin());
-
- // Save the current node count before the move is searched
- nodes = pos.nodes_searched();
-
- // If it's time to send nodes info, do it here where we have the
- // correct accumulated node counts searched by each thread.
- if (SendSearchedNodes)
- {
- SendSearchedNodes = false;
- cout << "info nodes " << nodes
- << " nps " << nps(pos)
- << " time " << current_search_time() << endl;
- }
-
- if (current_search_time() >= 1000)
- cout << "info currmove " << move
- << " currmovenumber " << moveCount << endl;
-
- moveIsCheck = pos.move_is_check(move);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- // Step 11. Decide the new search depth
- ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
- newDepth = depth + ext;
-
- // Step 12. Futility pruning (omitted at root)
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Step extra. pv search
- // We do pv search for PV moves
- if (isPvMove)
- {
- // Aspiration window is disabled in multi-pv case
- if (MultiPV > 1)
- alpha = -VALUE_INFINITE;
-
- // Full depth PV search, done on first move or after a fail high
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
- }
- else
- {
- // Step 14. Reduced search
- // if the move fails high will be re-searched at full depth
- bool doFullDepthSearch = true;
-
- if ( depth >= 3 * ONE_PLY
- && !captureOrPromotion
- && !dangerous
- && !move_is_castle(move)
- && ss->killers[0] != move
- && ss->killers[1] != move)
- {
- ss->reduction = reduction<PV>(depth, moveCount - MultiPV + 1);
-
- if (ss->reduction)
- {
- Depth d = newDepth - ss->reduction;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, 1);
-
- doFullDepthSearch = (value > alpha);
- }
- ss->reduction = DEPTH_ZERO; // Restore original reduction
- }
-
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- // Full depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
-
- // If we are above alpha then research at same depth but as PV
- // to get a correct score or eventually a fail high above beta.
- if (value > alpha)
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
- }
- }
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- // Finished searching the move. If StopRequest is true, the search
- // was aborted because the user interrupted the search or because we
- // ran out of time. In this case, the return value of the search cannot
- // be trusted, and we break out of the loop without updating the best
- // move and/or PV.
- if (StopRequest)
- break;
-
- // Remember searched nodes counts for this move
- rm->nodes += pos.nodes_searched() - nodes;
-
- // Step 17. Check for new best move
- if (!isPvMove && value <= alpha)
- rm->pv_score = -VALUE_INFINITE;
- else
- {
- // PV move or new best move!
-
- // Update PV
- ss->bestMove = move;
- rm->pv_score = value;
- rm->extract_pv_from_tt(pos);
-
- // We record how often the best move has been changed in each
- // iteration. This information is used for time managment: When
- // the best move changes frequently, we allocate some more time.
- if (!isPvMove && MultiPV == 1)
- BestMoveChangesByIteration[Iteration]++;
-
- // Inform GUI that PV has changed, in case of multi-pv UCI protocol
- // requires we send all the PV lines properly sorted.
- rml.sort_multipv(moveCount);
-
- for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
- cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
-
- // Update alpha. In multi-pv we don't use aspiration window
- if (MultiPV == 1)
- {
- // Raise alpha to setup proper non-pv search upper bound
- if (value > alpha)
- alpha = bestValue = value;
- }
- else // Set alpha equal to minimum score among the PV lines
- alpha = bestValue = rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
-
- } // PV move or new best move
-
- ++rm;
-
- } // Root moves loop
-
- // Step 20. Update tables
- // If the search is not aborted, update the transposition table,
- // history counters, and killer moves.
- if (!StopRequest)
- {
- move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
- vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
- : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
-
- TT.store(posKey, value_to_tt(bestValue, 0), vt, depth, move, ss->eval, ss->evalMargin);
-
- // Update killers and history only for non capture moves that fails high
- if ( bestValue >= beta
- && !pos.move_is_capture_or_promotion(move))
- {
- update_history(pos, move, depth, movesSearched, moveCount);
- update_killers(move, ss->killers);
- }
- }
-
- assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
-
- return bestValue;
- }
-
-
// search<>() is the main search function for both PV and non-PV nodes and for
// normal and SplitPoint nodes. When called just after a split point the search
// is simpler because we have already probed the hash table, done a null move
projects / stockfish / commitdiff