+/*
+ Glaurung, a UCI chess playing engine.
+ Copyright (C) 2004-2008 Tord Romstad
+
+ Glaurung is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ Glaurung is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+////
+//// Includes
+////
+
+#include <cassert>
+#include <cstdio>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+
+#include "book.h"
+#include "evaluate.h"
+#include "history.h"
+#include "misc.h"
+#include "movepick.h"
+#include "san.h"
+#include "search.h"
+#include "thread.h"
+#include "tt.h"
+#include "ucioption.h"
+
+
+////
+//// Local definitions
+////
+
+namespace {
+
+ /// Types
+
+ // The RootMove class is used for moves at the root at the tree. For each
+ // root move, we store a score, a node count, and a PV (really a refutation
+ // in the case of moves which fail low).
+
+ class RootMove {
+
+ public:
+ RootMove();
+ Move move;
+ Value score;
+ int64_t nodes, cumulativeNodes;
+ Move pv[PLY_MAX_PLUS_2];
+ };
+
+
+ // The RootMoveList class is essentially an array of RootMove objects, with
+ // a handful of methods for accessing the data in the individual moves.
+
+ class RootMoveList {
+
+ public:
+ RootMoveList(Position &pos, Move searchMoves[]);
+ Move get_move(int moveNum) const;
+ Value get_move_score(int moveNum) const;
+ void set_move_score(int moveNum, Value score);
+ void set_move_nodes(int moveNum, int64_t nodes);
+ void set_move_pv(int moveNum, const Move pv[]);
+ Move get_move_pv(int moveNum, int i) const;
+ int64_t get_move_cumulative_nodes(int moveNum);
+ int move_count() const;
+ Move scan_for_easy_move() const;
+ void sort();
+ void sort_multipv(int n);
+
+ private:
+ static int compare_root_moves(const RootMove &rm1, const RootMove &rm2);
+ static const int MaxRootMoves = 500;
+ RootMove moves[MaxRootMoves];
+ int count;
+ };
+
+
+ /// Constants and variables
+
+ // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV
+ // nodes:
+ int LMRPVMoves = 15;
+ int LMRNonPVMoves = 4;
+
+ // Depth limit for use of dynamic threat detection:
+ Depth ThreatDepth = 5*OnePly;
+
+ // Depth limit for selective search:
+ Depth SelectiveDepth = 7*OnePly;
+
+ // Use internal iterative deepening?
+ const bool UseIIDAtPVNodes = true;
+ const bool UseIIDAtNonPVNodes = false;
+
+ // Internal iterative deepening margin. At Non-PV moves, when
+ // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
+ // when the static evaluation is at most IIDMargin below beta.
+ const Value IIDMargin = Value(0x100);
+
+ // Use easy moves?
+ const bool UseEasyMove = true;
+
+ // Easy move margin. An easy move candidate must be at least this much
+ // better than the second best move.
+ const Value EasyMoveMargin = Value(0x200);
+
+ // Problem margin. If the score of the first move at iteration N+1 has
+ // dropped by more than this since iteration N, the boolean variable
+ // "Problem" is set to true, which will make the program spend some extra
+ // time looking for a better move.
+ const Value ProblemMargin = Value(0x28);
+
+ // No problem margin. If the boolean "Problem" is true, and a new move
+ // is found at the root which is less than NoProblemMargin worse than the
+ // best move from the previous iteration, Problem is set back to false.
+ const Value NoProblemMargin = Value(0x14);
+
+ // Null move margin. A null move search will not be done if the approximate
+ // evaluation of the position is more than NullMoveMargin below beta.
+ const Value NullMoveMargin = Value(0x300);
+
+ // Pruning criterions. See the code and comments in ok_to_prune() to
+ // understand their precise meaning.
+ const bool PruneEscapeMoves = false;
+ const bool PruneDefendingMoves = false;
+ const bool PruneBlockingMoves = false;
+
+ // Use futility pruning?
+ bool UseQSearchFutilityPruning = true;
+ bool UseFutilityPruning = true;
+
+ // Margins for futility pruning in the quiescence search, at frontier
+ // nodes, and at pre-frontier nodes:
+ Value FutilityMargin0 = Value(0x80);
+ Value FutilityMargin1 = Value(0x100);
+ Value FutilityMargin2 = Value(0x300);
+
+ // Razoring
+ Depth RazorDepth = 4*OnePly;
+ Value RazorMargin = Value(0x300);
+
+ // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
+ Depth CheckExtension[2] = {OnePly, OnePly};
+ Depth SingleReplyExtension[2] = {OnePly / 2, OnePly / 2};
+ Depth PawnPushTo7thExtension[2] = {OnePly / 2, OnePly / 2};
+ Depth PassedPawnExtension[2] = {Depth(0), Depth(0)};
+ Depth PawnEndgameExtension[2] = {OnePly, OnePly};
+ Depth MateThreatExtension[2] = {Depth(0), Depth(0)};
+
+ // Search depth at iteration 1:
+ const Depth InitialDepth = OnePly /*+ OnePly/2*/;
+
+ // Node counters
+ int NodesSincePoll;
+ int NodesBetweenPolls = 30000;
+
+ // Iteration counter:
+ int Iteration;
+
+ // Scores and number of times the best move changed for each iteration:
+ Value ValueByIteration[PLY_MAX_PLUS_2];
+ int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
+
+ // MultiPV mode:
+ int MultiPV = 1;
+
+ // Time managment variables
+ int SearchStartTime;
+ int MaxNodes, MaxDepth;
+ int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
+ Move BestRootMove, PonderMove, EasyMove;
+ int RootMoveNumber;
+ bool InfiniteSearch;
+ bool PonderSearch;
+ bool StopOnPonderhit;
+ bool AbortSearch;
+ bool Quit;
+ bool FailHigh;
+ bool Problem;
+ bool PonderingEnabled;
+ int ExactMaxTime;
+
+ // Show current line?
+ bool ShowCurrentLine = false;
+
+ // Log file
+ bool UseLogFile = false;
+ std::ofstream LogFile;
+
+ // MP related variables
+ Depth MinimumSplitDepth = 4*OnePly;
+ int MaxThreadsPerSplitPoint = 4;
+ Thread Threads[THREAD_MAX];
+ Lock MPLock;
+ bool AllThreadsShouldExit = false;
+ const int MaxActiveSplitPoints = 8;
+ SplitPoint SplitPointStack[THREAD_MAX][MaxActiveSplitPoints];
+ bool Idle = true;
+
+#if !defined(_MSC_VER)
+ pthread_cond_t WaitCond;
+ pthread_mutex_t WaitLock;
+#else
+ HANDLE SitIdleEvent[THREAD_MAX];
+#endif
+
+
+ /// Functions
+
+ void id_loop(const Position &pos, Move searchMoves[]);
+ Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml);
+ Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
+ Depth depth, int ply, int threadID);
+ Value search(Position &pos, SearchStack ss[], Value beta,
+ Depth depth, int ply, bool allowNullmove, int threadID);
+ Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
+ Depth depth, int ply, int threadID);
+ void sp_search(SplitPoint *sp, int threadID);
+ void sp_search_pv(SplitPoint *sp, int threadID);
+ void init_search_stack(SearchStack ss[]);
+ void init_node(const Position &pos, SearchStack ss[], int ply, int threadID);
+ void update_pv(SearchStack ss[], int ply);
+ void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
+ bool connected_moves(const Position &pos, Move m1, Move m2);
+ Depth extension(const Position &pos, Move m, bool pvNode, bool check,
+ bool singleReply, bool mateThreat);
+ bool ok_to_do_nullmove(const Position &pos);
+ bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
+
+ bool fail_high_ply_1();
+ int current_search_time();
+ int nps();
+ void poll();
+ void ponderhit();
+ void print_current_line(SearchStack ss[], int ply, int threadID);
+ void wait_for_stop_or_ponderhit();
+
+ void idle_loop(int threadID, SplitPoint *waitSp);
+ void init_split_point_stack();
+ void destroy_split_point_stack();
+ bool thread_should_stop(int threadID);
+ bool thread_is_available(int slave, int master);
+ bool idle_thread_exists(int master);
+ bool split(const Position &pos, SearchStack *ss, int ply,
+ Value *alpha, Value *beta, Value *bestValue, Depth depth,
+ int *moves, MovePicker *mp, Bitboard dcCandidates, int master,
+ bool pvNode);
+ void wake_sleeping_threads();
+
+#if !defined(_MSC_VER)
+ void *init_thread(void *threadID);
+#else
+ DWORD WINAPI init_thread(LPVOID threadID);
+#endif
+
+}
+
+
+////
+//// Global variables
+////
+
+// The main transposition table
+TranspositionTable TT = TranspositionTable(TTDefaultSize);
+
+
+// Number of active threads:
+int ActiveThreads = 1;
+
+// Locks. In principle, there is no need for IOLock to be a global variable,
+// but it could turn out to be useful for debugging.
+Lock IOLock;
+
+History H; // Should be made local?
+
+
+////
+//// Functions
+////
+
+/// think() is the external interface to Glaurung's search, and is called when
+/// the program receives the UCI 'go' command. It initializes various
+/// search-related global variables, and calls root_search()
+
+void think(const Position &pos, bool infinite, bool ponder, int time,
+ int increment, int movesToGo, int maxDepth, int maxNodes,
+ int maxTime, Move searchMoves[]) {
+
+ // Look for a book move:
+ if(!infinite && !ponder && get_option_value_bool("OwnBook")) {
+ Move bookMove;
+ if(get_option_value_string("Book File") != OpeningBook.file_name()) {
+ OpeningBook.close();
+ OpeningBook.open("book.bin");
+ }
+ bookMove = OpeningBook.get_move(pos);
+ if(bookMove != MOVE_NONE) {
+ std::cout << "bestmove " << bookMove << std::endl;
+ return;
+ }
+ }
+
+ // Initialize global search variables:
+ Idle = false;
+ SearchStartTime = get_system_time();
+ BestRootMove = MOVE_NONE;
+ PonderMove = MOVE_NONE;
+ EasyMove = MOVE_NONE;
+ for(int i = 0; i < THREAD_MAX; i++) {
+ Threads[i].nodes = 0ULL;
+ Threads[i].failHighPly1 = false;
+ }
+ NodesSincePoll = 0;
+ InfiniteSearch = infinite;
+ PonderSearch = ponder;
+ StopOnPonderhit = false;
+ AbortSearch = false;
+ Quit = false;
+ FailHigh = false;
+ Problem = false;
+ ExactMaxTime = maxTime;
+
+ // Read UCI option values:
+ TT.set_size(get_option_value_int("Hash"));
+ if(button_was_pressed("Clear Hash"))
+ TT.clear();
+ PonderingEnabled = get_option_value_int("Ponder");
+ MultiPV = get_option_value_int("MultiPV");
+
+ CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
+ CheckExtension[0] =
+ Depth(get_option_value_int("Check Extension (non-PV nodes)"));
+ SingleReplyExtension[1] = Depth(get_option_value_int("Single Reply Extension (PV nodes)"));
+ SingleReplyExtension[0] =
+ Depth(get_option_value_int("Single Reply Extension (non-PV nodes)"));
+ PawnPushTo7thExtension[1] =
+ Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
+ PawnPushTo7thExtension[0] =
+ Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
+ PassedPawnExtension[1] =
+ Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
+ PassedPawnExtension[0] =
+ Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
+ PawnEndgameExtension[1] =
+ Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
+ PawnEndgameExtension[0] =
+ Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
+ MateThreatExtension[1] =
+ Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
+ MateThreatExtension[0] =
+ Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
+
+ LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
+ LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
+ ThreatDepth = get_option_value_int("Threat Depth") * OnePly;
+ SelectiveDepth = get_option_value_int("Selective Plies") * OnePly;
+
+ Chess960 = get_option_value_bool("UCI_Chess960");
+ ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine");
+ UseLogFile = get_option_value_bool("Use Search Log");
+ if(UseLogFile)
+ LogFile.open(get_option_value_string("Search Log Filename").c_str(),
+ std::ios::out | std::ios::app);
+
+ UseQSearchFutilityPruning =
+ get_option_value_bool("Futility Pruning (Quiescence Search)");
+ UseFutilityPruning =
+ get_option_value_bool("Futility Pruning (Main Search)");
+
+ FutilityMargin0 =
+ value_from_centipawns(get_option_value_int("Futility Margin 0"));
+ FutilityMargin1 =
+ value_from_centipawns(get_option_value_int("Futility Margin 1"));
+ FutilityMargin2 =
+ value_from_centipawns(get_option_value_int("Futility Margin 2"));
+
+ RazorDepth = (get_option_value_int("Maximum Razoring Depth") + 1) * OnePly;
+ RazorMargin = value_from_centipawns(get_option_value_int("Razoring Margin"));
+
+ MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly;
+ MaxThreadsPerSplitPoint =
+ get_option_value_int("Maximum Number of Threads per Split Point");
+
+ read_weights(pos.side_to_move());
+
+ int newActiveThreads = get_option_value_int("Threads");
+ if(newActiveThreads != ActiveThreads) {
+ ActiveThreads = newActiveThreads;
+ init_eval(ActiveThreads);
+ }
+
+ // Write information to search log file:
+ if(UseLogFile) {
+ LogFile << "Searching: " << pos.to_fen() << '\n';
+ LogFile << "infinite: " << infinite << " ponder: " << ponder
+ << " time: " << time << " increment: " << increment
+ << " moves to go: " << movesToGo << '\n';
+ }
+
+ // Wake up sleeping threads:
+ wake_sleeping_threads();
+
+ for(int i = 1; i < ActiveThreads; i++)
+ assert(thread_is_available(i, 0));
+
+ // Set thinking time:
+ if(!movesToGo) { // Sudden death time control
+ if(increment) {
+ MaxSearchTime = time / 30 + increment;
+ AbsoluteMaxSearchTime = Max(time / 4, increment - 100);
+ }
+ else { // Blitz game without increment
+ MaxSearchTime = time / 40;
+ AbsoluteMaxSearchTime = time / 8;
+ }
+ }
+ else { // (x moves) / (y minutes)
+ if(movesToGo == 1) {
+ MaxSearchTime = time / 2;
+ AbsoluteMaxSearchTime = Min(time / 2, time - 500);
+ }
+ else {
+ MaxSearchTime = time / Min(movesToGo, 20);
+ AbsoluteMaxSearchTime = Min((4 * time) / movesToGo, time / 3);
+ }
+ }
+ if(PonderingEnabled) {
+ MaxSearchTime += MaxSearchTime / 4;
+ MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime);
+ }
+
+ // Fixed depth or fixed number of nodes?
+ MaxDepth = maxDepth;
+ if(MaxDepth)
+ InfiniteSearch = true; // HACK
+
+ MaxNodes = maxNodes;
+ if(MaxNodes) {
+ NodesBetweenPolls = Min(MaxNodes, 30000);
+ InfiniteSearch = true; // HACK
+ }
+ else
+ NodesBetweenPolls = 30000;
+
+ // We're ready to start thinking. Call the iterative deepening loop
+ // function:
+ id_loop(pos, searchMoves);
+
+ if(UseLogFile)
+ LogFile.close();
+
+ if(Quit) {
+ OpeningBook.close();
+ stop_threads();
+ quit_eval();
+ exit(0);
+ }
+
+ Idle = true;
+}
+
+
+/// init_threads() is called during startup. It launches all helper threads,
+/// and initializes the split point stack and the global locks and condition
+/// objects.
+
+void init_threads() {
+ volatile int i;
+#if !defined(_MSC_VER)
+ pthread_t pthread[1];
+#endif
+
+ for(i = 0; i < THREAD_MAX; i++)
+ Threads[i].activeSplitPoints = 0;
+
+ // Initialize global locks:
+ lock_init(&MPLock, NULL);
+ lock_init(&IOLock, NULL);
+
+ init_split_point_stack();
+
+#if !defined(_MSC_VER)
+ pthread_mutex_init(&WaitLock, NULL);
+ pthread_cond_init(&WaitCond, NULL);
+#else
+ for(i = 0; i < THREAD_MAX; i++)
+ SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0);
+#endif
+
+ // All threads except the main thread should be initialized to idle state:
+ for(i = 1; i < THREAD_MAX; i++) {
+ Threads[i].stop = false;
+ Threads[i].workIsWaiting = false;
+ Threads[i].idle = true;
+ Threads[i].running = false;
+ }
+
+ // Launch the helper threads:
+ for(i = 1; i < THREAD_MAX; i++) {
+#if !defined(_MSC_VER)
+ pthread_create(pthread, NULL, init_thread, (void*)(&i));
+#else
+ {
+ DWORD iID[1];
+ CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID);
+ }
+#endif
+
+ // Wait until the thread has finished launching:
+ while(!Threads[i].running);
+ }
+}
+
+
+/// stop_threads() is called when the program exits. It makes all the
+/// helper threads exit cleanly.
+
+void stop_threads() {
+ ActiveThreads = THREAD_MAX; // HACK
+ Idle = false; // HACK
+ wake_sleeping_threads();
+ AllThreadsShouldExit = true;
+ for(int i = 1; i < THREAD_MAX; i++) {
+ Threads[i].stop = true;
+ while(Threads[i].running);
+ }
+ destroy_split_point_stack();
+}
+
+
+/// nodes_searched() returns the total number of nodes searched so far in
+/// the current search.
+
+int64_t nodes_searched() {
+ int64_t result = 0ULL;
+ for(int i = 0; i < ActiveThreads; i++)
+ result += Threads[i].nodes;
+ return result;
+}
+
+
+namespace {
+
+ // id_loop() is the main iterative deepening loop. It calls root_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.
+
+ void id_loop(const Position &pos, Move searchMoves[]) {
+ Position p(pos);
+ RootMoveList rml(p, searchMoves);
+ SearchStack ss[PLY_MAX_PLUS_2];
+
+ // Initialize
+ TT.new_search();
+ H.clear();
+ init_search_stack(ss);
+
+ ValueByIteration[0] = Value(0);
+ ValueByIteration[1] = rml.get_move_score(0);
+ Iteration = 1;
+
+ EasyMove = rml.scan_for_easy_move();
+
+ // Iterative deepening loop
+ while(!AbortSearch && Iteration < PLY_MAX) {
+
+ // Initialize iteration
+ rml.sort();
+ Iteration++;
+ BestMoveChangesByIteration[Iteration] = 0;
+ if(Iteration <= 5)
+ ExtraSearchTime = 0;
+
+ std::cout << "info depth " << Iteration << std::endl;
+
+ // Search to the current depth
+ ValueByIteration[Iteration] = root_search(p, ss, rml);
+
+ // Erase the easy move if it differs from the new best move
+ if(ss[0].pv[0] != EasyMove)
+ EasyMove = MOVE_NONE;
+
+ Problem = false;
+
+ if(!InfiniteSearch) {
+ // Time to stop?
+ bool stopSearch = false;
+
+ // Stop search early if there is only a single legal move:
+ if(Iteration >= 6 && rml.move_count() == 1)
+ stopSearch = true;
+
+ // Stop search early when the last two iterations returned a mate
+ // score:
+ if(Iteration >= 6
+ && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
+ && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
+ stopSearch = true;
+
+ // Stop search early if one move seems to be much better than the
+ // rest:
+ int64_t nodes = nodes_searched();
+ if(Iteration >= 8 && EasyMove == ss[0].pv[0] &&
+ ((rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 &&
+ current_search_time() > MaxSearchTime / 16) ||
+ (rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100 &&
+ current_search_time() > MaxSearchTime / 32)))
+ stopSearch = true;
+
+ // Add some extra time if the best move has changed during the last
+ // two iterations:
+ if(Iteration > 5 && Iteration <= 50)
+ ExtraSearchTime =
+ BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2) +
+ BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
+
+ // Stop search if most of MaxSearchTime is consumed at the end of the
+ // iteration. We probably don't have enough time to search the first
+ // move at the next iteration anyway.
+ if(current_search_time() > ((MaxSearchTime + ExtraSearchTime)*80) / 128)
+ stopSearch = true;
+
+ if(stopSearch) {
+ if(!PonderSearch)
+ break;
+ else
+ StopOnPonderhit = true;
+ }
+ }
+
+ // Write PV to transposition table, in case the relevant entries have
+ // been overwritten during the search:
+ TT.insert_pv(p, ss[0].pv);
+
+ if(MaxDepth && Iteration >= MaxDepth)
+ break;
+ }
+
+ rml.sort();
+
+ // If we are pondering, we shouldn't print the best move before we
+ // are told to do so
+ if(PonderSearch)
+ wait_for_stop_or_ponderhit();
+ else
+ // Print final search statistics
+ std::cout << "info nodes " << nodes_searched() << " nps " << nps()
+ << " time " << current_search_time()
+ << " hashfull " << TT.full() << std::endl;
+
+ // Print the best move and the ponder move to the standard output:
+ std::cout << "bestmove " << ss[0].pv[0];
+ if(ss[0].pv[1] != MOVE_NONE)
+ std::cout << " ponder " << ss[0].pv[1];
+ std::cout << std::endl;
+
+ if(UseLogFile) {
+ UndoInfo u;
+ LogFile << "Nodes: " << nodes_searched() << '\n';
+ LogFile << "Nodes/second: " << nps() << '\n';
+ LogFile << "Best move: " << move_to_san(p, ss[0].pv[0]) << '\n';
+ p.do_move(ss[0].pv[0], u);
+ LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1]) << '\n';
+ LogFile << std::endl;
+ }
+ }
+
+
+ // root_search() is the function which searches the root node. It is
+ // similar to search_pv except that it uses a different move ordering
+ // scheme (perhaps we should try to use this at internal PV nodes, too?)
+ // and prints some information to the standard output.
+
+ Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml) {
+ Value alpha = -VALUE_INFINITE, beta = VALUE_INFINITE, value;
+ Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
+
+ // Loop through all the moves in the root move list:
+ for(int i = 0; i < rml.move_count() && !AbortSearch; i++) {
+ int64_t nodes;
+ Move move;
+ UndoInfo u;
+ Depth ext, newDepth;
+
+ RootMoveNumber = i + 1;
+ FailHigh = false;
+
+ // Remember the node count before the move is searched. The node counts
+ // are used to sort the root moves at the next iteration.
+ nodes = nodes_searched();
+
+ // Pick the next root move, and print the move and the move number to
+ // the standard output:
+ move = ss[0].currentMove = rml.get_move(i);
+ if(current_search_time() >= 1000)
+ std::cout << "info currmove " << move
+ << " currmovenumber " << i + 1 << std::endl;
+
+ // Decide search depth for this move:
+ ext = extension(pos, move, true, pos.move_is_check(move), false, false);
+ newDepth = (Iteration-2)*OnePly + ext + InitialDepth;
+
+ // Make the move, and search it.
+ pos.do_move(move, u, dcCandidates);
+
+ if(i < MultiPV) {
+ value = -search_pv(pos, ss, -beta, VALUE_INFINITE, newDepth, 1, 0);
+ // If the value has dropped a lot compared to the last iteration,
+ // set the boolean variable Problem to true. This variable is used
+ // for time managment: When Problem is true, we try to complete the
+ // current iteration before playing a move.
+ Problem = (Iteration >= 2 &&
+ value <= ValueByIteration[Iteration-1] - ProblemMargin);
+ if(Problem && StopOnPonderhit)
+ StopOnPonderhit = false;
+ }
+ else {
+ value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
+ if(value > alpha) {
+ // Fail high! Set the boolean variable FailHigh to true, and
+ // re-search the move with a big window. The variable FailHigh is
+ // used for time managment: We try to avoid aborting the search
+ // prematurely during a fail high research.
+ FailHigh = true;
+ value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
+ }
+ }
+
+ pos.undo_move(move, u);
+
+ // Finished searching the move. If AbortSearch 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(AbortSearch)
+ break;
+
+ // Remember the node count for this move. The node counts are used to
+ // sort the root moves at the next iteration.
+ rml.set_move_nodes(i, nodes_searched() - nodes);
+
+ assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
+
+ if(value <= alpha && i >= MultiPV)
+ rml.set_move_score(i, -VALUE_INFINITE);
+ else {
+ // New best move!
+
+ // Update PV:
+ rml.set_move_score(i, value);
+ update_pv(ss, 0);
+ rml.set_move_pv(i, ss[0].pv);
+
+ if(MultiPV == 1) {
+ // 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(i > 0)
+ BestMoveChangesByIteration[Iteration]++;
+
+ // Print search information to the standard output:
+ std::cout << "info depth " << Iteration
+ << " score " << value_to_string(value)
+ << " time " << current_search_time()
+ << " nodes " << nodes_searched()
+ << " nps " << nps()
+ << " pv ";
+ for(int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
+ std::cout << ss[0].pv[j] << " ";
+ std::cout << std::endl;
+
+ if(UseLogFile)
+ LogFile << pretty_pv(pos, current_search_time(), Iteration,
+ nodes_searched(), value, ss[0].pv)
+ << std::endl;
+
+ alpha = value;
+
+ // Reset the global variable Problem to false if the value isn't too
+ // far below the final value from the last iteration.
+ if(value > ValueByIteration[Iteration - 1] - NoProblemMargin)
+ Problem = false;
+ }
+ else { // MultiPV > 1
+ rml.sort_multipv(i);
+ for(int j = 0; j < Min(MultiPV, rml.move_count()); j++) {
+ int k;
+ std::cout << "info multipv " << j + 1
+ << " score " << value_to_string(rml.get_move_score(j))
+ << " depth " << ((j <= i)? Iteration : Iteration - 1)
+ << " time " << current_search_time()
+ << " nodes " << nodes_searched()
+ << " nps " << nps()
+ << " pv ";
+ for(k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++)
+ std::cout << rml.get_move_pv(j, k) << " ";
+ std::cout << std::endl;
+ }
+ alpha = rml.get_move_score(Min(i, MultiPV-1));
+ }
+ }
+ }
+ return alpha;
+ }
+
+
+ // search_pv() is the main search function for PV nodes.
+
+ Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
+ Depth depth, int ply, int threadID) {
+ assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
+ assert(beta > alpha && beta <= VALUE_INFINITE);
+ assert(ply >= 0 && ply < PLY_MAX);
+ assert(threadID >= 0 && threadID < ActiveThreads);
+
+ EvalInfo ei;
+
+ // Initialize, and make an early exit in case of an aborted search,
+ // an instant draw, maximum ply reached, etc.
+ Value oldAlpha = alpha;
+
+ if(AbortSearch || thread_should_stop(threadID))
+ return Value(0);
+
+ if(depth < OnePly)
+ return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
+
+ init_node(pos, ss, ply, threadID);
+
+ if(pos.is_draw())
+ return VALUE_DRAW;
+
+ if(ply >= PLY_MAX - 1)
+ return evaluate(pos, ei, threadID);
+
+ // Mate distance pruning
+ alpha = Max(value_mated_in(ply), alpha);
+ beta = Min(value_mate_in(ply+1), beta);
+ if(alpha >= beta)
+ return alpha;
+
+ // Transposition table lookup. At PV nodes, we don't use the TT for
+ // pruning, but only for move ordering.
+ Value ttValue;
+ Depth ttDepth;
+ Move ttMove = MOVE_NONE;
+ ValueType ttValueType;
+
+ TT.retrieve(pos, &ttValue, &ttDepth, &ttMove, &ttValueType);
+
+ // Internal iterative deepening.
+ if(UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly) {
+ search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
+ ttMove = ss[ply].pv[ply];
+ }
+
+ // Initialize a MovePicker object for the current position, and prepare
+ // to search all moves:
+ MovePicker mp = MovePicker(pos, true, ttMove, ss[ply].mateKiller,
+ ss[ply].killer1, ss[ply].killer2, depth);
+ Move move, movesSearched[256];
+ int moveCount = 0;
+ Value value, bestValue = -VALUE_INFINITE;
+ Bitboard dcCandidates = mp.discovered_check_candidates();
+ bool mateThreat =
+ MateThreatExtension[1] > Depth(0)
+ && pos.has_mate_threat(opposite_color(pos.side_to_move()));
+
+ // Loop through all legal moves until no moves remain or a beta cutoff
+ // occurs.
+ while(alpha < beta && !thread_should_stop(threadID)
+ && (move = mp.get_next_move()) != MOVE_NONE) {
+ UndoInfo u;
+ Depth ext, newDepth;
+ bool singleReply = (pos.is_check() && mp.number_of_moves() == 1);
+ bool moveIsCheck = pos.move_is_check(move, dcCandidates);
+ bool moveIsCapture = pos.move_is_capture(move);
+ bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
+
+ assert(move_is_ok(move));
+ movesSearched[moveCount++] = ss[ply].currentMove = move;
+
+ ss[ply].currentMoveCaptureValue = move_is_ep(move)?
+ PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
+
+ // Decide the new search depth.
+ ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat);
+ newDepth = depth - OnePly + ext;
+
+ // Make and search the move.
+ pos.do_move(move, u, dcCandidates);
+
+ if(moveCount == 1)
+ value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
+ else {
+ if(depth >= 2*OnePly && ext == Depth(0) && moveCount >= LMRPVMoves
+ && !moveIsCapture && !move_promotion(move)
+ && !moveIsPassedPawnPush && !move_is_castle(move)
+ && move != ss[ply].killer1 && move != ss[ply].killer2) {
+ ss[ply].reduction = OnePly;
+ value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true,
+ threadID);
+ }
+ else value = alpha + 1;
+ if(value > alpha) {
+ ss[ply].reduction = Depth(0);
+ value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
+ if(value > alpha && value < beta) {
+ if(ply == 1 && RootMoveNumber == 1)
+ // When the search fails high at ply 1 while searching the first
+ // move at the root, set the flag failHighPly1. This is used for
+ // time managment: We don't want to stop the search early in
+ // such cases, because resolving the fail high at ply 1 could
+ // result in a big drop in score at the root.
+ Threads[threadID].failHighPly1 = true;
+ value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1,
+ threadID);
+ Threads[threadID].failHighPly1 = false;
+ }
+ }
+ }
+ pos.undo_move(move, u);
+
+ assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+
+ // New best move?
+ if(value > bestValue) {
+ bestValue = value;
+ if(value > alpha) {
+ alpha = value;
+ update_pv(ss, ply);
+ if(value == value_mate_in(ply + 1))
+ ss[ply].mateKiller = move;
+ }
+ // If we are at ply 1, and we are searching the first root move at
+ // ply 0, set the 'Problem' variable if the score has dropped a lot
+ // (from the computer's point of view) since the previous iteration:
+ if(Iteration >= 2 &&
+ -value <= ValueByIteration[Iteration-1] - ProblemMargin)
+ Problem = true;
+ }
+
+ // Split?
+ if(ActiveThreads > 1 && bestValue < beta && depth >= MinimumSplitDepth
+ && Iteration <= 99 && idle_thread_exists(threadID)
+ && !AbortSearch && !thread_should_stop(threadID)
+ && split(pos, ss, ply, &alpha, &beta, &bestValue, depth,
+ &moveCount, &mp, dcCandidates, threadID, true))
+ break;
+ }
+
+ // All legal moves have been searched. A special case: If there were
+ // no legal moves, it must be mate or stalemate:
+ if(moveCount == 0) {
+ if(pos.is_check())
+ return value_mated_in(ply);
+ else
+ return VALUE_DRAW;
+ }
+
+ // If the search is not aborted, update the transposition table,
+ // history counters, and killer moves. This code is somewhat messy,
+ // and definitely needs to be cleaned up. FIXME
+ if(!AbortSearch && !thread_should_stop(threadID)) {
+ if(bestValue <= oldAlpha)
+ TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE,
+ VALUE_TYPE_UPPER);
+ else if(bestValue >= beta) {
+ Move m = ss[ply].pv[ply];
+ if(pos.square_is_empty(move_to(m)) && !move_promotion(m) &&
+ !move_is_ep(m)) {
+ for(int i = 0; i < moveCount - 1; i++)
+ if(pos.square_is_empty(move_to(movesSearched[i]))
+ && !move_promotion(movesSearched[i])
+ && !move_is_ep(movesSearched[i]))
+ H.failure(pos.piece_on(move_from(movesSearched[i])),
+ movesSearched[i]);
+
+ H.success(pos.piece_on(move_from(m)), m, depth);
+
+ if(m != ss[ply].killer1) {
+ ss[ply].killer2 = ss[ply].killer1;
+ ss[ply].killer1 = m;
+ }
+ }
+ TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
+ }
+ else
+ TT.store(pos, value_to_tt(bestValue, ply), depth, ss[ply].pv[ply],
+ VALUE_TYPE_EXACT);
+ }
+
+ return bestValue;
+ }
+
+
+ // search() is the search function for zero-width nodes.
+
+ Value search(Position &pos, SearchStack ss[], Value beta, Depth depth,
+ int ply, bool allowNullmove, int threadID) {
+ assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+ assert(ply >= 0 && ply < PLY_MAX);
+ assert(threadID >= 0 && threadID < ActiveThreads);
+
+ EvalInfo ei;
+
+ // Initialize, and make an early exit in case of an aborted search,
+ // an instant draw, maximum ply reached, etc.
+ if(AbortSearch || thread_should_stop(threadID))
+ return Value(0);
+
+ if(depth < OnePly)
+ return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
+
+ init_node(pos, ss, ply, threadID);
+
+ if(pos.is_draw())
+ return VALUE_DRAW;
+
+ if(ply >= PLY_MAX - 1)
+ return evaluate(pos, ei, threadID);
+
+ // Mate distance pruning
+ if(value_mated_in(ply) >= beta)
+ return beta;
+ if(value_mate_in(ply+1) < beta)
+ return beta-1;
+
+ // Transposition table lookup
+ bool ttFound;
+ Value ttValue;
+ Depth ttDepth;
+ Move ttMove = MOVE_NONE;
+ ValueType ttValueType;
+
+ ttFound = TT.retrieve(pos, &ttValue, &ttDepth, &ttMove, &ttValueType);
+ if(ttFound) {
+ ttValue = value_from_tt(ttValue, ply);
+ if(ttDepth >= depth
+ || ttValue >= Max(value_mate_in(100), beta)
+ || ttValue < Min(value_mated_in(100), beta)) {
+ if((is_lower_bound(ttValueType) && ttValue >= beta) ||
+ (is_upper_bound(ttValueType) && ttValue < beta)) {
+ ss[ply].currentMove = ttMove;
+ return ttValue;
+ }
+ }
+ }
+
+ Value approximateEval = quick_evaluate(pos);
+ bool mateThreat = false;
+
+ // Null move search
+ if(!pos.is_check() && allowNullmove && ok_to_do_nullmove(pos)
+ && approximateEval >= beta - NullMoveMargin) {
+ UndoInfo u;
+ Value nullValue;
+
+ ss[ply].currentMove = MOVE_NULL;
+ pos.do_null_move(u);
+ nullValue = -search(pos, ss, -(beta-1), depth-4*OnePly, ply+1, false,
+ threadID);
+ pos.undo_null_move(u);
+
+ if(nullValue >= beta) {
+ if(depth >= 6 * OnePly) { // Do zugzwang verification search
+ Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
+ if(v >= beta)
+ return beta;
+ }
+ else
+ return beta;
+ }
+ else {
+ // The null move failed low, which means that we may be faced with
+ // some kind of threat. If the previous move was reduced, check if
+ // the move that refuted the null move was somehow connected to the
+ // move which was reduced. If a connection is found, return a fail
+ // low score (which will cause the reduced move to fail high in the
+ // parent node, which will trigger a re-search with full depth).
+ if(nullValue == value_mated_in(ply+2))
+ mateThreat = true;
+ ss[ply].threatMove = ss[ply+1].currentMove;
+ if(depth < ThreatDepth && ss[ply-1].reduction &&
+ connected_moves(pos, ss[ply-1].currentMove, ss[ply].threatMove))
+ return beta - 1;
+ }
+ }
+ // Razoring:
+ else if(depth < RazorDepth && approximateEval < beta - RazorMargin &&
+ evaluate(pos, ei, threadID) < beta - RazorMargin) {
+ Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
+ if(v < beta)
+ return v;
+ }
+
+ // Internal iterative deepening
+ if(UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
+ evaluate(pos, ei, threadID) >= beta - IIDMargin) {
+ search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
+ ttMove = ss[ply].pv[ply];
+ }
+
+ // Initialize a MovePicker object for the current position, and prepare
+ // to search all moves:
+ MovePicker mp = MovePicker(pos, false, ttMove, ss[ply].mateKiller,
+ ss[ply].killer1, ss[ply].killer2, depth);
+ Move move, movesSearched[256];
+ int moveCount = 0;
+ Value value, bestValue = -VALUE_INFINITE, futilityValue = VALUE_NONE;
+ Bitboard dcCandidates = mp.discovered_check_candidates();
+ bool isCheck = pos.is_check();
+ bool useFutilityPruning =
+ UseFutilityPruning && depth < SelectiveDepth && !isCheck;
+
+ // Loop through all legal moves until no moves remain or a beta cutoff
+ // occurs.
+ while(bestValue < beta && !thread_should_stop(threadID)
+ && (move = mp.get_next_move()) != MOVE_NONE) {
+ UndoInfo u;
+ Depth ext, newDepth;
+ bool singleReply = (isCheck && mp.number_of_moves() == 1);
+ bool moveIsCheck = pos.move_is_check(move, dcCandidates);
+ bool moveIsCapture = pos.move_is_capture(move);
+ bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
+
+ assert(move_is_ok(move));
+ movesSearched[moveCount++] = ss[ply].currentMove = move;
+
+ // Decide the new search depth.
+ ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat);
+ newDepth = depth - OnePly + ext;
+
+ // Futility pruning
+ if(useFutilityPruning && ext == Depth(0) && !moveIsCapture &&
+ !moveIsPassedPawnPush && !move_promotion(move)) {
+
+ if(moveCount >= 2 + int(depth)
+ && ok_to_prune(pos, move, ss[ply].threatMove, depth))
+ continue;
+
+ if(depth < 3 * OnePly && approximateEval < beta) {
+ if(futilityValue == VALUE_NONE)
+ futilityValue = evaluate(pos, ei, threadID)
+ + ((depth < 2 * OnePly)? FutilityMargin1 : FutilityMargin2);
+ if(futilityValue < beta) {
+ if(futilityValue > bestValue)
+ bestValue = futilityValue;
+ continue;
+ }
+ }
+ }
+
+ // Make and search the move.
+ pos.do_move(move, u, dcCandidates);
+
+ if(depth >= 2*OnePly && ext == Depth(0) && moveCount >= LMRNonPVMoves
+ && !moveIsCapture && !move_promotion(move) && !moveIsPassedPawnPush
+ && !move_is_castle(move)
+ && move != ss[ply].killer1 && move != ss[ply].killer2) {
+ ss[ply].reduction = OnePly;
+ value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true,
+ threadID);
+ }
+ else
+ value = beta;
+ if(value >= beta) {
+ ss[ply].reduction = Depth(0);
+ value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
+ }
+ pos.undo_move(move, u);
+
+ assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+
+ // New best move?
+ if(value > bestValue) {
+ bestValue = value;
+ if(value >= beta)
+ update_pv(ss, ply);
+ if(value == value_mate_in(ply + 1))
+ ss[ply].mateKiller = move;
+ }
+
+ // Split?
+ if(ActiveThreads > 1 && bestValue < beta && depth >= MinimumSplitDepth
+ && Iteration <= 99 && idle_thread_exists(threadID)
+ && !AbortSearch && !thread_should_stop(threadID)
+ && split(pos, ss, ply, &beta, &beta, &bestValue, depth, &moveCount,
+ &mp, dcCandidates, threadID, false))
+ break;
+ }
+
+ // All legal moves have been searched. A special case: If there were
+ // no legal moves, it must be mate or stalemate:
+ if(moveCount == 0) {
+ if(pos.is_check())
+ return value_mated_in(ply);
+ else
+ return VALUE_DRAW;
+ }
+
+ // If the search is not aborted, update the transposition table,
+ // history counters, and killer moves. This code is somewhat messy,
+ // and definitely needs to be cleaned up. FIXME
+ if(!AbortSearch && !thread_should_stop(threadID)) {
+ if(bestValue < beta)
+ TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE,
+ VALUE_TYPE_UPPER);
+ else {
+ Move m = ss[ply].pv[ply];
+
+ if(pos.square_is_empty(move_to(m)) && !move_promotion(m) &&
+ !move_is_ep(m)) {
+ for(int i = 0; i < moveCount - 1; i++)
+ if(pos.square_is_empty(move_to(movesSearched[i]))
+ && !move_promotion(movesSearched[i])
+ && !move_is_ep(movesSearched[i]))
+ H.failure(pos.piece_on(move_from(movesSearched[i])),
+ movesSearched[i]);
+ H.success(pos.piece_on(move_from(m)), m, depth);
+
+ if(m != ss[ply].killer1) {
+ ss[ply].killer2 = ss[ply].killer1;
+ ss[ply].killer1 = m;
+ }
+ }
+ TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
+ }
+ }
+
+ return bestValue;
+ }
+
+
+ // qsearch() is the quiescence search function, which is called by the main
+ // search function when the remaining depth is zero (or, to be more precise,
+ // less than OnePly).
+
+ Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
+ Depth depth, int ply, int threadID) {
+ Value staticValue, bestValue, value;
+ EvalInfo ei;
+
+ assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
+ assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+ assert(depth <= 0);
+ assert(ply >= 0 && ply < PLY_MAX);
+ assert(threadID >= 0 && threadID < ActiveThreads);
+
+ // Initialize, and make an early exit in case of an aborted search,
+ // an instant draw, maximum ply reached, etc.
+ if(AbortSearch || thread_should_stop(threadID))
+ return Value(0);
+
+ init_node(pos, ss, ply, threadID);
+
+ if(pos.is_draw())
+ return VALUE_DRAW;
+
+ // Evaluate the position statically:
+ staticValue = evaluate(pos, ei, threadID);
+
+ if(ply == PLY_MAX - 1) return staticValue;
+
+ // Initialize "stand pat score", and return it immediately if it is
+ // at least beta.
+ if(pos.is_check())
+ bestValue = -VALUE_INFINITE;
+ else {
+ bestValue = staticValue;
+ if(bestValue >= beta)
+ return bestValue;
+ if(bestValue > alpha)
+ alpha = bestValue;
+ }
+
+ // Initialize a MovePicker object for the current position, and prepare
+ // to search the moves. Because the depth is <= 0 here, only captures,
+ // queen promotions and checks (only if depth == 0) will be generated.
+ MovePicker mp = MovePicker(pos, false, MOVE_NONE, MOVE_NONE, MOVE_NONE,
+ MOVE_NONE, depth);
+ Move move;
+ int moveCount = 0;
+ Bitboard dcCandidates = mp.discovered_check_candidates();
+ bool isCheck = pos.is_check();
+
+ // Loop through the moves until no moves remain or a beta cutoff
+ // occurs.
+ while(alpha < beta && ((move = mp.get_next_move()) != MOVE_NONE)) {
+ UndoInfo u;
+ bool moveIsCheck = pos.move_is_check(move, dcCandidates);
+ bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
+
+ assert(move_is_ok(move));
+
+ moveCount++;
+ ss[ply].currentMove = move;
+
+ // Futility pruning
+ if(UseQSearchFutilityPruning && !isCheck && !moveIsCheck &&
+ !move_promotion(move) && !moveIsPassedPawnPush &&
+ beta - alpha == 1 &&
+ pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame) {
+ Value futilityValue =
+ staticValue
+ + Max(pos.midgame_value_of_piece_on(move_to(move)),
+ pos.endgame_value_of_piece_on(move_to(move)))
+ + FutilityMargin0
+ + ei.futilityMargin;
+ if(futilityValue < alpha) {
+ if(futilityValue > bestValue)
+ bestValue = futilityValue;
+ continue;
+ }
+ }
+
+ // Don't search captures and checks with negative SEE values.
+ if(!isCheck && !move_promotion(move) &&
+ pos.midgame_value_of_piece_on(move_from(move)) >
+ pos.midgame_value_of_piece_on(move_to(move)) &&
+ pos.see(move) < 0)
+ continue;
+
+ // Make and search the move.
+ pos.do_move(move, u, dcCandidates);
+ value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
+ pos.undo_move(move, u);
+
+ assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+
+ // New best move?
+ if(value > bestValue) {
+ bestValue = value;
+ if(value > alpha) {
+ alpha = value;
+ update_pv(ss, ply);
+ }
+ }
+ }
+
+ // All legal moves have been searched. A special case: If we're in check
+ // and no legal moves were found, it is checkmate:
+ if(pos.is_check() && moveCount == 0) // Mate!
+ return value_mated_in(ply);
+
+ assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
+
+ return bestValue;
+ }
+
+
+ // sp_search() is used to search from a split point. This function is called
+ // by each thread working at the split point. It is similar to the normal
+ // search() function, but simpler. Because we have already probed the hash
+ // table, done a null move search, and searched the first move before
+ // splitting, we don't have to repeat all this work in sp_search(). We
+ // also don't need to store anything to the hash table here: This is taken
+ // care of after we return from the split point.
+
+ void sp_search(SplitPoint *sp, int threadID) {
+ assert(threadID >= 0 && threadID < ActiveThreads);
+ assert(ActiveThreads > 1);
+
+ Position pos = Position(sp->pos);
+ SearchStack *ss = sp->sstack[threadID];
+ Value value;
+ Move move;
+ int moveCount = sp->moves;
+ bool isCheck = pos.is_check();
+ bool useFutilityPruning =
+ UseFutilityPruning && sp->depth < SelectiveDepth && !isCheck;
+
+ while(sp->bestValue < sp->beta && !thread_should_stop(threadID)
+ && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE) {
+ UndoInfo u;
+ Depth ext, newDepth;
+ bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
+ bool moveIsCapture = pos.move_is_capture(move);
+ bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
+
+ assert(move_is_ok(move));
+
+ lock_grab(&(sp->lock));
+ sp->moves++;
+ moveCount = sp->moves;
+ lock_release(&(sp->lock));
+
+ ss[sp->ply].currentMove = move;
+
+ // Decide the new search depth.
+ ext = extension(pos, move, false, moveIsCheck, false, false);
+ newDepth = sp->depth - OnePly + ext;
+
+ // Prune?
+ if(useFutilityPruning && ext == Depth(0) && !moveIsCapture
+ && !moveIsPassedPawnPush && !move_promotion(move)
+ && moveCount >= 2 + int(sp->depth)
+ && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
+ continue;
+
+ // Make and search the move.
+ pos.do_move(move, u, sp->dcCandidates);
+ if(ext == Depth(0) && moveCount >= LMRNonPVMoves
+ && !moveIsCapture && !move_promotion(move) && !moveIsPassedPawnPush
+ && !move_is_castle(move)
+ && move != ss[sp->ply].killer1 && move != ss[sp->ply].killer2) {
+ ss[sp->ply].reduction = OnePly;
+ value = -search(pos, ss, -(sp->beta-1), newDepth - OnePly, sp->ply+1,
+ true, threadID);
+ }
+ else
+ value = sp->beta;
+ if(value >= sp->beta) {
+ ss[sp->ply].reduction = Depth(0);
+ value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true,
+ threadID);
+ }
+ pos.undo_move(move, u);
+
+ assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+
+ if(thread_should_stop(threadID))
+ break;
+
+ // New best move?
+ lock_grab(&(sp->lock));
+ if(value > sp->bestValue && !thread_should_stop(threadID)) {
+ sp->bestValue = value;
+ if(sp->bestValue >= sp->beta) {
+ sp_update_pv(sp->parentSstack, ss, sp->ply);
+ for(int i = 0; i < ActiveThreads; i++)
+ if(i != threadID && (i == sp->master || sp->slaves[i]))
+ Threads[i].stop = true;
+ sp->finished = true;
+ }
+ }
+ lock_release(&(sp->lock));
+ }
+
+ lock_grab(&(sp->lock));
+
+ // If this is the master thread and we have been asked to stop because of
+ // a beta cutoff higher up in the tree, stop all slave threads:
+ if(sp->master == threadID && thread_should_stop(threadID))
+ for(int i = 0; i < ActiveThreads; i++)
+ if(sp->slaves[i])
+ Threads[i].stop = true;
+
+ sp->cpus--;
+ sp->slaves[threadID] = 0;
+
+ lock_release(&(sp->lock));
+ }
+
+
+ // sp_search_pv() is used to search from a PV split point. This function
+ // is called by each thread working at the split point. It is similar to
+ // the normal search_pv() function, but simpler. Because we have already
+ // probed the hash table and searched the first move before splitting, we
+ // don't have to repeat all this work in sp_search_pv(). We also don't
+ // need to store anything to the hash table here: This is taken care of
+ // after we return from the split point.
+
+ void sp_search_pv(SplitPoint *sp, int threadID) {
+ assert(threadID >= 0 && threadID < ActiveThreads);
+ assert(ActiveThreads > 1);
+
+ Position pos = Position(sp->pos);
+ SearchStack *ss = sp->sstack[threadID];
+ Value value;
+ Move move;
+ int moveCount = sp->moves;
+
+ while(sp->alpha < sp->beta && !thread_should_stop(threadID)
+ && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE) {
+ UndoInfo u;
+ Depth ext, newDepth;
+ bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
+ bool moveIsCapture = pos.move_is_capture(move);
+ bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
+
+ assert(move_is_ok(move));
+
+ ss[sp->ply].currentMoveCaptureValue = move_is_ep(move)?
+ PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
+
+ lock_grab(&(sp->lock));
+ sp->moves++;
+ moveCount = sp->moves;
+ lock_release(&(sp->lock));
+
+ ss[sp->ply].currentMove = move;
+
+ // Decide the new search depth.
+ ext = extension(pos, move, true, moveIsCheck, false, false);
+ newDepth = sp->depth - OnePly + ext;
+
+ // Make and search the move.
+ pos.do_move(move, u, sp->dcCandidates);
+ if(ext == Depth(0) && moveCount >= LMRPVMoves && !moveIsCapture
+ && !move_promotion(move) && !moveIsPassedPawnPush
+ && !move_is_castle(move)
+ && move != ss[sp->ply].killer1 && move != ss[sp->ply].killer2) {
+ ss[sp->ply].reduction = OnePly;
+ value = -search(pos, ss, -sp->alpha, newDepth - OnePly, sp->ply+1,
+ true, threadID);
+ }
+ else
+ value = sp->alpha + 1;
+ if(value > sp->alpha) {
+ ss[sp->ply].reduction = Depth(0);
+ value = -search(pos, ss, -sp->alpha, newDepth, sp->ply+1, true,
+ threadID);
+ if(value > sp->alpha && value < sp->beta) {
+ if(sp->ply == 1 && RootMoveNumber == 1)
+ // When the search fails high at ply 1 while searching the first
+ // move at the root, set the flag failHighPly1. This is used for
+ // time managment: We don't want to stop the search early in
+ // such cases, because resolving the fail high at ply 1 could
+ // result in a big drop in score at the root.
+ Threads[threadID].failHighPly1 = true;
+ value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth,
+ sp->ply+1, threadID);
+ Threads[threadID].failHighPly1 = false;
+ }
+ }
+ pos.undo_move(move, u);
+
+ assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+
+ if(thread_should_stop(threadID))
+ break;
+
+ // New best move?
+ lock_grab(&(sp->lock));
+ if(value > sp->bestValue && !thread_should_stop(threadID)) {
+ sp->bestValue = value;
+ if(value > sp->alpha) {
+ sp->alpha = value;
+ sp_update_pv(sp->parentSstack, ss, sp->ply);
+ if(value == value_mate_in(sp->ply + 1))
+ ss[sp->ply].mateKiller = move;
+ if(value >= sp->beta) {
+ for(int i = 0; i < ActiveThreads; i++)
+ if(i != threadID && (i == sp->master || sp->slaves[i]))
+ Threads[i].stop = true;
+ sp->finished = true;
+ }
+ }
+ // If we are at ply 1, and we are searching the first root move at
+ // ply 0, set the 'Problem' variable if the score has dropped a lot
+ // (from the computer's point of view) since the previous iteration:
+ if(Iteration >= 2 &&
+ -value <= ValueByIteration[Iteration-1] - ProblemMargin)
+ Problem = true;
+ }
+ lock_release(&(sp->lock));
+ }
+
+ lock_grab(&(sp->lock));
+
+ // If this is the master thread and we have been asked to stop because of
+ // a beta cutoff higher up in the tree, stop all slave threads:
+ if(sp->master == threadID && thread_should_stop(threadID))
+ for(int i = 0; i < ActiveThreads; i++)
+ if(sp->slaves[i])
+ Threads[i].stop = true;
+
+ sp->cpus--;
+ sp->slaves[threadID] = 0;
+
+ lock_release(&(sp->lock));
+ }
+
+
+ /// The RootMove class
+
+ // Constructor
+
+ RootMove::RootMove() {
+ nodes = cumulativeNodes = 0ULL;
+ }
+
+
+ /// The RootMoveList class
+
+ // Constructor
+
+ RootMoveList::RootMoveList(Position &pos, Move searchMoves[]) {
+ MoveStack mlist[MaxRootMoves];
+ bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
+ int i, j = 0, k;
+
+ // Generate all legal moves
+ count = generate_legal_moves(pos, mlist);
+
+ // Add each move to the moves[] array
+ for(i = 0; i < count; i++) {
+ UndoInfo u;
+ SearchStack ss[PLY_MAX_PLUS_2];
+ bool includeMove;
+
+ if(includeAllMoves)
+ includeMove = true;
+ else {
+ includeMove = false;
+ for(k = 0; searchMoves[k] != MOVE_NONE; k++)
+ if(searchMoves[k] == mlist[i].move) {
+ includeMove = true;
+ break;
+ }
+ }
+
+ if(includeMove) {
+ moves[j].move = mlist[i].move;
+ moves[j].nodes = 0ULL;
+ pos.do_move(moves[j].move, u);
+ moves[j].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE,
+ Depth(0), 1, 0);
+ pos.undo_move(moves[j].move, u);
+ moves[j].pv[0] = moves[i].move;
+ moves[j].pv[1] = MOVE_NONE; // FIXME
+ j++;
+ }
+ }
+ count = j;
+ this->sort();
+ }
+
+
+ // Simple accessor methods for the RootMoveList class
+
+ Move RootMoveList::get_move(int moveNum) const {
+ return moves[moveNum].move;
+ }
+
+ Value RootMoveList::get_move_score(int moveNum) const {
+ return moves[moveNum].score;
+ }
+
+ void RootMoveList::set_move_score(int moveNum, Value score) {
+ moves[moveNum].score = score;
+ }
+
+ void RootMoveList::set_move_nodes(int moveNum, int64_t nodes) {
+ moves[moveNum].nodes = nodes;
+ moves[moveNum].cumulativeNodes += nodes;
+ }
+
+ void RootMoveList::set_move_pv(int moveNum, const Move pv[]) {
+ int j;
+ for(j = 0; pv[j] != MOVE_NONE; j++)
+ moves[moveNum].pv[j] = pv[j];
+ moves[moveNum].pv[j] = MOVE_NONE;
+ }
+
+ Move RootMoveList::get_move_pv(int moveNum, int i) const {
+ return moves[moveNum].pv[i];
+ }
+
+ int64_t RootMoveList::get_move_cumulative_nodes(int moveNum) {
+ return moves[moveNum].cumulativeNodes;
+ }
+
+ int RootMoveList::move_count() const {
+ return count;
+ }
+
+
+ // RootMoveList::scan_for_easy_move() is called at the end of the first
+ // iteration, and is used to detect an "easy move", i.e. a move which appears
+ // to be much bester than all the rest. If an easy move is found, the move
+ // is returned, otherwise the function returns MOVE_NONE. It is very
+ // important that this function is called at the right moment: The code
+ // assumes that the first iteration has been completed and the moves have
+ // been sorted.
+
+ Move RootMoveList::scan_for_easy_move() const {
+ Value bestMoveValue = this->get_move_score(0);
+ for(int i = 1; i < this->move_count(); i++)
+ if(this->get_move_score(i) >= bestMoveValue - EasyMoveMargin)
+ return MOVE_NONE;
+ return this->get_move(0);
+ }
+
+
+ // RootMoveList::sort() sorts the root move list at the beginning of a new
+ // iteration.
+
+ void RootMoveList::sort() {
+ for(int i = 1; i < count; i++) {
+ RootMove rm = moves[i];
+ int j;
+ for(j = i; j > 0 && compare_root_moves(moves[j-1], rm); j--)
+ moves[j] = moves[j-1];
+ moves[j] = rm;
+ }
+ }
+
+
+ // RootMoveList::sort_multipv() sorts the first few moves in the root move
+ // list by their scores and depths. It is used to order the different PVs
+ // correctly in MultiPV mode.
+
+ void RootMoveList::sort_multipv(int n) {
+ for(int i = 1; i <= n; i++) {
+ RootMove rm = moves[i];
+ int j;
+ for(j = i; j > 0 && moves[j-1].score < rm.score; j--)
+ moves[j] = moves[j-1];
+ moves[j] = rm;
+ }
+ }
+
+
+ // RootMoveList::compare_root_moves() is the comparison function used by
+ // RootMoveList::sort when sorting the moves. A move m1 is considered to
+ // be better than a move m2 if it has a higher score, or if the moves have
+ // equal score but m1 has the higher node count.
+
+ int RootMoveList::compare_root_moves(const RootMove &rm1,
+ const RootMove &rm2) {
+ if(rm1.score < rm2.score) return 1;
+ else if(rm1.score > rm2.score) return 0;
+ else if(rm1.nodes < rm2.nodes) return 1;
+ else if(rm1.nodes > rm2.nodes) return 0;
+ else return 1;
+ }
+
+
+ // init_search_stack() initializes a search stack at the beginning of a
+ // new search from the root.
+
+ void init_search_stack(SearchStack ss[]) {
+ for(int i = 0; i < 3; i++) {
+ ss[i].pv[i] = MOVE_NONE;
+ ss[i].pv[i+1] = MOVE_NONE;
+ ss[i].currentMove = MOVE_NONE;
+ ss[i].mateKiller = MOVE_NONE;
+ ss[i].killer1 = MOVE_NONE;
+ ss[i].killer2 = MOVE_NONE;
+ ss[i].threatMove = MOVE_NONE;
+ ss[i].reduction = Depth(0);
+ }
+ }
+
+
+ // init_node() is called at the beginning of all the search functions
+ // (search(), search_pv(), qsearch(), and so on) and initializes the search
+ // stack object corresponding to the current node. Once every
+ // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
+ // for user input and checks whether it is time to stop the search.
+
+ void init_node(const Position &pos, SearchStack ss[], int ply, int threadID) {
+ assert(ply >= 0 && ply < PLY_MAX);
+ assert(threadID >= 0 && threadID < ActiveThreads);
+
+ Threads[threadID].nodes++;
+
+ if(threadID == 0) {
+ NodesSincePoll++;
+ if(NodesSincePoll >= NodesBetweenPolls) {
+ poll();
+ NodesSincePoll = 0;
+ }
+ }
+
+ ss[ply].pv[ply] = ss[ply].pv[ply+1] = ss[ply].currentMove = MOVE_NONE;
+ ss[ply+2].mateKiller = MOVE_NONE;
+ ss[ply+2].killer1 = ss[ply+2].killer2 = MOVE_NONE;
+ ss[ply].threatMove = MOVE_NONE;
+ ss[ply].reduction = Depth(0);
+ ss[ply].currentMoveCaptureValue = Value(0);
+
+ if(Threads[threadID].printCurrentLine)
+ print_current_line(ss, ply, threadID);
+ }
+
+
+ // update_pv() is called whenever a search returns a value > alpha. It
+ // updates the PV in the SearchStack object corresponding to the current
+ // node.
+
+ void update_pv(SearchStack ss[], int ply) {
+ assert(ply >= 0 && ply < PLY_MAX);
+
+ ss[ply].pv[ply] = ss[ply].currentMove;
+ int p;
+ for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
+ ss[ply].pv[p] = ss[ply+1].pv[p];
+ ss[ply].pv[p] = MOVE_NONE;
+ }
+
+
+ // sp_update_pv() is a variant of update_pv for use at split points. The
+ // difference between the two functions is that sp_update_pv also updates
+ // the PV at the parent node.
+
+ void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply) {
+ assert(ply >= 0 && ply < PLY_MAX);
+
+ ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove;
+ int p;
+ for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
+ ss[ply].pv[p] = pss[ply].pv[p] = ss[ply+1].pv[p];
+ ss[ply].pv[p] = pss[ply].pv[p] = MOVE_NONE;
+ }
+
+
+ // connected_moves() tests whether two moves are 'connected' in the sense
+ // that the first move somehow made the second move possible (for instance
+ // if the moving piece is the same in both moves). The first move is
+ // assumed to be the move that was made to reach the current position, while
+ // the second move is assumed to be a move from the current position.
+
+ bool connected_moves(const Position &pos, Move m1, Move m2) {
+ Square f1, t1, f2, t2;
+
+ assert(move_is_ok(m1));
+ assert(move_is_ok(m2));
+
+ if(m2 == MOVE_NONE)
+ return false;
+
+ // Case 1: The moving piece is the same in both moves.
+ f2 = move_from(m2);
+ t1 = move_to(m1);
+ if(f2 == t1)
+ return true;
+
+ // Case 2: The destination square for m2 was vacated by m1.
+ t2 = move_to(m2);
+ f1 = move_from(m1);
+ if(t2 == f1)
+ return true;
+
+ // Case 3: Moving through the vacated square:
+ if(piece_is_slider(pos.piece_on(f2)) &&
+ bit_is_set(squares_between(f2, t2), f1))
+ return true;
+
+ // Case 4: The destination square for m2 is attacked by the moving piece
+ // in m1:
+ if(pos.piece_attacks_square(t1, t2))
+ return true;
+
+ // Case 5: Discovered check, checking piece is the piece moved in m1:
+ if(piece_is_slider(pos.piece_on(t1)) &&
+ bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())),
+ f2) &&
+ !bit_is_set(squares_between(t2, pos.king_square(pos.side_to_move())),
+ t2)) {
+ Bitboard occ = pos.occupied_squares();
+ Color us = pos.side_to_move();
+ Square ksq = pos.king_square(us);
+ clear_bit(&occ, f2);
+ if(pos.type_of_piece_on(t1) == BISHOP) {
+ if(bit_is_set(bishop_attacks_bb(ksq, occ), t1))
+ return true;
+ }
+ else if(pos.type_of_piece_on(t1) == ROOK) {
+ if(bit_is_set(rook_attacks_bb(ksq, occ), t1))
+ return true;
+ }
+ else {
+ assert(pos.type_of_piece_on(t1) == QUEEN);
+ if(bit_is_set(queen_attacks_bb(ksq, occ), t1))
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+
+ // extension() decides whether a move should be searched with normal depth,
+ // or with extended depth. Certain classes of moves (checking moves, in
+ // particular) are searched with bigger depth than ordinary moves.
+
+ Depth extension(const Position &pos, Move m, bool pvNode,
+ bool check, bool singleReply, bool mateThreat) {
+ Depth result = Depth(0);
+
+ if(check)
+ result += CheckExtension[pvNode];
+ if(singleReply)
+ result += SingleReplyExtension[pvNode];
+ if(pos.move_is_pawn_push_to_7th(m))
+ result += PawnPushTo7thExtension[pvNode];
+ if(pos.move_is_passed_pawn_push(m))
+ result += PassedPawnExtension[pvNode];
+ if(mateThreat)
+ result += MateThreatExtension[pvNode];
+ if(pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame
+ && (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
+ - pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
+ && !move_promotion(m))
+ result += PawnEndgameExtension[pvNode];
+ if(pvNode && pos.move_is_capture(m)
+ && pos.type_of_piece_on(move_to(m)) != PAWN && pos.see(m) >= 0)
+ result += OnePly/2;
+
+ return Min(result, OnePly);
+ }
+
+
+ // ok_to_do_nullmove() looks at the current position and decides whether
+ // doing a 'null move' should be allowed. In order to avoid zugzwang
+ // problems, null moves are not allowed when the side to move has very
+ // little material left. Currently, the test is a bit too simple: Null
+ // moves are avoided only when the side to move has only pawns left. It's
+ // probably a good idea to avoid null moves in at least some more
+ // complicated endgames, e.g. KQ vs KR. FIXME
+
+ bool ok_to_do_nullmove(const Position &pos) {
+ if(pos.non_pawn_material(pos.side_to_move()) == Value(0))
+ return false;
+ return true;
+ }
+
+
+ // ok_to_prune() tests whether it is safe to forward prune a move. Only
+ // non-tactical moves late in the move list close to the leaves are
+ // candidates for pruning.
+
+ bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d) {
+ Square mfrom, mto, tfrom, tto;
+
+ assert(move_is_ok(m));
+ assert(threat == MOVE_NONE || move_is_ok(threat));
+ assert(!move_promotion(m));
+ assert(!pos.move_is_check(m));
+ assert(!pos.move_is_capture(m));
+ assert(!pos.move_is_passed_pawn_push(m));
+ assert(d >= OnePly);
+
+ mfrom = move_from(m);
+ mto = move_to(m);
+ tfrom = move_from(threat);
+ tto = move_to(threat);
+
+ // Case 1: Castling moves are never pruned.
+ if(move_is_castle(m))
+ return false;
+
+ // Case 2: Don't prune moves which move the threatened piece
+ if(!PruneEscapeMoves && threat != MOVE_NONE && mfrom == tto)
+ return false;
+
+ // Case 3: If the threatened piece has value less than or equal to the
+ // value of the threatening piece, don't prune move which defend it.
+ if(!PruneDefendingMoves && threat != MOVE_NONE
+ && (piece_value_midgame(pos.piece_on(tfrom))
+ >= piece_value_midgame(pos.piece_on(tto)))
+ && pos.move_attacks_square(m, tto))
+ return false;
+
+ // Case 4: Don't prune moves with good history.
+ if(!H.ok_to_prune(pos.piece_on(move_from(m)), m, d))
+ return false;
+
+ // Case 5: If the moving piece in the threatened move is a slider, don't
+ // prune safe moves which block its ray.
+ if(!PruneBlockingMoves && threat != MOVE_NONE
+ && piece_is_slider(pos.piece_on(tfrom))
+ && bit_is_set(squares_between(tfrom, tto), mto) && pos.see(m) >= 0)
+ return false;
+
+ return true;
+ }
+
+
+ // fail_high_ply_1() checks if some thread is currently resolving a fail
+ // high at ply 1 at the node below the first root node. This information
+ // is used for time managment.
+
+ bool fail_high_ply_1() {
+ for(int i = 0; i < ActiveThreads; i++)
+ if(Threads[i].failHighPly1)
+ return true;
+ return false;
+ }
+
+
+ // current_search_time() returns the number of milliseconds which have passed
+ // since the beginning of the current search.
+
+ int current_search_time() {
+ return get_system_time() - SearchStartTime;
+ }
+
+
+ // nps() computes the current nodes/second count.
+
+ int nps() {
+ int t = current_search_time();
+ return (t > 0)? int((nodes_searched() * 1000) / t) : 0;
+ }
+
+
+ // poll() performs two different functions: It polls for user input, and it
+ // looks at the time consumed so far and decides if it's time to abort the
+ // search.
+
+ void poll() {
+ int t, data;
+ static int lastInfoTime;
+
+ t = current_search_time();
+
+ // Poll for input
+ data = Bioskey();
+ if(data) {
+ char input[256];
+ if(fgets(input, 255, stdin) == NULL)
+ strcpy(input, "quit\n");
+ if(strncmp(input, "quit", 4) == 0) {
+ AbortSearch = true;
+ PonderSearch = false;
+ Quit = true;
+ }
+ else if(strncmp(input, "stop", 4) == 0) {
+ AbortSearch = true;
+ PonderSearch = false;
+ }
+ else if(strncmp(input, "ponderhit", 9) == 0)
+ ponderhit();
+ }
+
+ // Print search information
+ if(t < 1000)
+ lastInfoTime = 0;
+ else if(lastInfoTime > t)
+ // HACK: Must be a new search where we searched less than
+ // NodesBetweenPolls nodes during the first second of search.
+ lastInfoTime = 0;
+ else if(t - lastInfoTime >= 1000) {
+ lastInfoTime = t;
+ lock_grab(&IOLock);
+ std::cout << "info nodes " << nodes_searched() << " nps " << nps()
+ << " time " << t << " hashfull " << TT.full() << std::endl;
+ lock_release(&IOLock);
+ if(ShowCurrentLine)
+ Threads[0].printCurrentLine = true;
+ }
+
+ // Should we stop the search?
+ if(!PonderSearch && Iteration >= 2 &&
+ (!InfiniteSearch && (t > AbsoluteMaxSearchTime ||
+ (RootMoveNumber == 1 &&
+ t > MaxSearchTime + ExtraSearchTime) ||
+ (!FailHigh && !fail_high_ply_1() && !Problem &&
+ t > 6*(MaxSearchTime + ExtraSearchTime)))))
+ AbortSearch = true;
+
+ if(!PonderSearch && ExactMaxTime && t >= ExactMaxTime)
+ AbortSearch = true;
+
+ if(!PonderSearch && Iteration >= 3 && MaxNodes
+ && nodes_searched() >= MaxNodes)
+ AbortSearch = true;
+ }
+
+
+ // ponderhit() is called when the program is pondering (i.e. thinking while
+ // it's the opponent's turn to move) in order to let the engine know that
+ // it correctly predicted the opponent's move.
+
+ void ponderhit() {
+ int t = current_search_time();
+ PonderSearch = false;
+ if(Iteration >= 2 &&
+ (!InfiniteSearch && (StopOnPonderhit ||
+ t > AbsoluteMaxSearchTime ||
+ (RootMoveNumber == 1 &&
+ t > MaxSearchTime + ExtraSearchTime) ||
+ (!FailHigh && !fail_high_ply_1() && !Problem &&
+ t > 6*(MaxSearchTime + ExtraSearchTime)))))
+ AbortSearch = true;
+ }
+
+
+ // print_current_line() prints the current line of search for a given
+ // thread. Called when the UCI option UCI_ShowCurrLine is 'true'.
+
+ void print_current_line(SearchStack ss[], int ply, int threadID) {
+ assert(ply >= 0 && ply < PLY_MAX);
+ assert(threadID >= 0 && threadID < ActiveThreads);
+
+ if(!Threads[threadID].idle) {
+ lock_grab(&IOLock);
+ std::cout << "info currline " << (threadID + 1);
+ for(int p = 0; p < ply; p++)
+ std::cout << " " << ss[p].currentMove;
+ std::cout << std::endl;
+ lock_release(&IOLock);
+ }
+ Threads[threadID].printCurrentLine = false;
+ if(threadID + 1 < ActiveThreads)
+ Threads[threadID + 1].printCurrentLine = true;
+ }
+
+
+ // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
+ // while the program is pondering. The point is to work around a wrinkle in
+ // the UCI protocol: When pondering, the engine is not allowed to give a
+ // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
+ // We simply wait here until one of these commands is sent, and return,
+ // after which the bestmove and pondermove will be printed (in id_loop()).
+
+ void wait_for_stop_or_ponderhit() {
+ std::string command;
+
+ while(true) {
+ if(!std::getline(std::cin, command))
+ command = "quit";
+
+ if(command == "quit") {
+ OpeningBook.close();
+ stop_threads();
+ quit_eval();
+ exit(0);
+ }
+ else if(command == "ponderhit" || command == "stop")
+ break;
+ }
+ }
+
+
+ // idle_loop() is where the threads are parked when they have no work to do.
+ // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
+ // object for which the current thread is the master.
+
+ void idle_loop(int threadID, SplitPoint *waitSp) {
+ assert(threadID >= 0 && threadID < THREAD_MAX);
+
+ Threads[threadID].running = true;
+
+ while(true) {
+ if(AllThreadsShouldExit && threadID != 0)
+ break;
+
+ // If we are not thinking, wait for a condition to be signaled instead
+ // of wasting CPU time polling for work:
+ while(threadID != 0 && (Idle || threadID >= ActiveThreads)) {
+#if !defined(_MSC_VER)
+ pthread_mutex_lock(&WaitLock);
+ if(Idle || threadID >= ActiveThreads)
+ pthread_cond_wait(&WaitCond, &WaitLock);
+ pthread_mutex_unlock(&WaitLock);
+#else
+ WaitForSingleObject(SitIdleEvent[threadID], INFINITE);
+#endif
+ }
+
+ // If this thread has been assigned work, launch a search:
+ if(Threads[threadID].workIsWaiting) {
+ Threads[threadID].workIsWaiting = false;
+ if(Threads[threadID].splitPoint->pvNode)
+ sp_search_pv(Threads[threadID].splitPoint, threadID);
+ else
+ sp_search(Threads[threadID].splitPoint, threadID);
+ Threads[threadID].idle = true;
+ }
+
+ // If this thread is the master of a split point and all threads have
+ // finished their work at this split point, return from the idle loop:
+ if(waitSp != NULL && waitSp->cpus == 0)
+ return;
+ }
+
+ Threads[threadID].running = false;
+ }
+
+
+ // init_split_point_stack() is called during program initialization, and
+ // initializes all split point objects.
+
+ void init_split_point_stack() {
+ for(int i = 0; i < THREAD_MAX; i++)
+ for(int j = 0; j < MaxActiveSplitPoints; j++) {
+ SplitPointStack[i][j].parent = NULL;
+ lock_init(&(SplitPointStack[i][j].lock), NULL);
+ }
+ }
+
+
+ // destroy_split_point_stack() is called when the program exits, and
+ // destroys all locks in the precomputed split point objects.
+
+ void destroy_split_point_stack() {
+ for(int i = 0; i < THREAD_MAX; i++)
+ for(int j = 0; j < MaxActiveSplitPoints; j++)
+ lock_destroy(&(SplitPointStack[i][j].lock));
+ }
+
+
+ // thread_should_stop() checks whether the thread with a given threadID has
+ // been asked to stop, directly or indirectly. This can happen if a beta
+ // cutoff has occured in thre thread's currently active split point, or in
+ // some ancestor of the current split point.
+
+ bool thread_should_stop(int threadID) {
+ assert(threadID >= 0 && threadID < ActiveThreads);
+
+ SplitPoint *sp;
+
+ if(Threads[threadID].stop)
+ return true;
+ if(ActiveThreads <= 2)
+ return false;
+ for(sp = Threads[threadID].splitPoint; sp != NULL; sp = sp->parent)
+ if(sp->finished) {
+ Threads[threadID].stop = true;
+ return true;
+ }
+ return false;
+ }
+
+
+ // thread_is_available() checks whether the thread with threadID "slave" is
+ // available to help the thread with threadID "master" at a split point. An
+ // obvious requirement is that "slave" must be idle. With more than two
+ // threads, this is not by itself sufficient: If "slave" is the master of
+ // some active split point, it is only available as a slave to the other
+ // threads which are busy searching the split point at the top of "slave"'s
+ // split point stack (the "helpful master concept" in YBWC terminology).
+
+ bool thread_is_available(int slave, int master) {
+ assert(slave >= 0 && slave < ActiveThreads);
+ assert(master >= 0 && master < ActiveThreads);
+ assert(ActiveThreads > 1);
+
+ if(!Threads[slave].idle || slave == master)
+ return false;
+
+ if(Threads[slave].activeSplitPoints == 0)
+ // No active split points means that the thread is available as a slave
+ // for any other thread.
+ return true;
+
+ if(ActiveThreads == 2)
+ return true;
+
+ // Apply the "helpful master" concept if possible.
+ if(SplitPointStack[slave][Threads[slave].activeSplitPoints-1].slaves[master])
+ return true;
+
+ return false;
+ }
+
+
+ // idle_thread_exists() tries to find an idle thread which is available as
+ // a slave for the thread with threadID "master".
+
+ bool idle_thread_exists(int master) {
+ assert(master >= 0 && master < ActiveThreads);
+ assert(ActiveThreads > 1);
+
+ for(int i = 0; i < ActiveThreads; i++)
+ if(thread_is_available(i, master))
+ return true;
+ return false;
+ }
+
+
+ // split() does the actual work of distributing the work at a node between
+ // several threads at PV nodes. If it does not succeed in splitting the
+ // node (because no idle threads are available, or because we have no unused
+ // split point objects), the function immediately returns false. If
+ // splitting is possible, a SplitPoint object is initialized with all the
+ // data that must be copied to the helper threads (the current position and
+ // search stack, alpha, beta, the search depth, etc.), and we tell our
+ // helper threads that they have been assigned work. This will cause them
+ // to instantly leave their idle loops and call sp_search_pv(). When all
+ // threads have returned from sp_search_pv (or, equivalently, when
+ // splitPoint->cpus becomes 0), split() returns true.
+
+ bool split(const Position &p, SearchStack *sstck, int ply,
+ Value *alpha, Value *beta, Value *bestValue,
+ Depth depth, int *moves,
+ MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode) {
+ assert(p.is_ok());
+ assert(sstck != NULL);
+ assert(ply >= 0 && ply < PLY_MAX);
+ assert(*bestValue >= -VALUE_INFINITE && *bestValue <= *alpha);
+ assert(!pvNode || *alpha < *beta);
+ assert(*beta <= VALUE_INFINITE);
+ assert(depth > Depth(0));
+ assert(master >= 0 && master < ActiveThreads);
+ assert(ActiveThreads > 1);
+
+ SplitPoint *splitPoint;
+ int i;
+
+ lock_grab(&MPLock);
+
+ // If no other thread is available to help us, or if we have too many
+ // active split points, don't split:
+ if(!idle_thread_exists(master) ||
+ Threads[master].activeSplitPoints >= MaxActiveSplitPoints) {
+ lock_release(&MPLock);
+ return false;
+ }
+
+ // Pick the next available split point object from the split point stack:
+ splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
+ Threads[master].activeSplitPoints++;
+
+ // Initialize the split point object:
+ splitPoint->parent = Threads[master].splitPoint;
+ splitPoint->finished = false;
+ splitPoint->ply = ply;
+ splitPoint->depth = depth;
+ splitPoint->alpha = pvNode? *alpha : (*beta - 1);
+ splitPoint->beta = *beta;
+ splitPoint->pvNode = pvNode;
+ splitPoint->dcCandidates = dcCandidates;
+ splitPoint->bestValue = *bestValue;
+ splitPoint->master = master;
+ splitPoint->mp = mp;
+ splitPoint->moves = *moves;
+ splitPoint->cpus = 1;
+ splitPoint->pos.copy(p);
+ splitPoint->parentSstack = sstck;
+ for(i = 0; i < ActiveThreads; i++)
+ splitPoint->slaves[i] = 0;
+
+ // Copy the current position and the search stack to the master thread:
+ memcpy(splitPoint->sstack[master], sstck, (ply+1)*sizeof(SearchStack));
+ Threads[master].splitPoint = splitPoint;
+
+ // Make copies of the current position and search stack for each thread:
+ for(i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint;
+ i++)
+ if(thread_is_available(i, master)) {
+ memcpy(splitPoint->sstack[i], sstck, (ply+1)*sizeof(SearchStack));
+ Threads[i].splitPoint = splitPoint;
+ splitPoint->slaves[i] = 1;
+ splitPoint->cpus++;
+ }
+
+ // Tell the threads that they have work to do. This will make them leave
+ // their idle loop.
+ for(i = 0; i < ActiveThreads; i++)
+ if(i == master || splitPoint->slaves[i]) {
+ Threads[i].workIsWaiting = true;
+ Threads[i].idle = false;
+ Threads[i].stop = false;
+ }
+
+ lock_release(&MPLock);
+
+ // Everything is set up. The master thread enters the idle loop, from
+ // which it will instantly launch a search, because its workIsWaiting
+ // slot is 'true'. We send the split point as a second parameter to the
+ // idle loop, which means that the main thread will return from the idle
+ // loop when all threads have finished their work at this split point
+ // (i.e. when // splitPoint->cpus == 0).
+ idle_loop(master, splitPoint);
+
+ // We have returned from the idle loop, which means that all threads are
+ // finished. Update alpha, beta and bestvalue, and return:
+ lock_grab(&MPLock);
+ if(pvNode) *alpha = splitPoint->alpha;
+ *beta = splitPoint->beta;
+ *bestValue = splitPoint->bestValue;
+ Threads[master].stop = false;
+ Threads[master].idle = false;
+ Threads[master].activeSplitPoints--;
+ Threads[master].splitPoint = splitPoint->parent;
+ lock_release(&MPLock);
+
+ return true;
+ }
+
+
+ // wake_sleeping_threads() wakes up all sleeping threads when it is time
+ // to start a new search from the root.
+
+ void wake_sleeping_threads() {
+ if(ActiveThreads > 1) {
+ for(int i = 1; i < ActiveThreads; i++) {
+ Threads[i].idle = true;
+ Threads[i].workIsWaiting = false;
+ }
+#if !defined(_MSC_VER)
+ pthread_mutex_lock(&WaitLock);
+ pthread_cond_broadcast(&WaitCond);
+ pthread_mutex_unlock(&WaitLock);
+#else
+ for(int i = 1; i < THREAD_MAX; i++)
+ SetEvent(SitIdleEvent[i]);
+#endif
+ }
+ }
+
+
+ // init_thread() is the function which is called when a new thread is
+ // launched. It simply calls the idle_loop() function with the supplied
+ // threadID. There are two versions of this function; one for POSIX threads
+ // and one for Windows threads.
+
+#if !defined(_MSC_VER)
+
+ void *init_thread(void *threadID) {
+ idle_loop(*(int *)threadID, NULL);
+ return NULL;
+ }
+
+#else
+
+ DWORD WINAPI init_thread(LPVOID threadID) {
+ idle_loop(*(int *)threadID, NULL);
+ return NULL;
+ }
+
+#endif
+
+}
projects / stockfish / commitdiff