/// Types
enum NodeType { NonPV, PV };
+ // Set to true to force running with one thread.
+ // Used for debugging SMP code.
+ const bool FakeSplit = false;
+
// ThreadsManager class is used to handle all the threads related stuff in search,
// init, starting, parking and, the most important, launching a slave thread at a
// split point are what this class does. All the access to shared thread data is
void wake_sleeping_threads();
void put_threads_to_sleep();
void idle_loop(int threadID, SplitPoint* sp);
+
+ template <bool Fake>
bool split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
Depth depth, bool mateThreat, int* moves, MovePicker* mp, int master, bool pvNode);
template <NodeType PvNode>
Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
+ template <NodeType PvNode>
+ void sp_search(SplitPoint* sp, int threadID);
+
template <NodeType PvNode>
Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
- void sp_search(SplitPoint* sp, int threadID);
- void sp_search_pv(SplitPoint* sp, int threadID);
void init_node(SearchStack ss[], int ply, int threadID);
void update_pv(SearchStack ss[], int ply);
void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply);
bestValue = value;
if (value > alpha)
{
- alpha = value;
+ if (PvNode && value < beta) // This guarantees that always: alpha < beta
+ alpha = value;
+
update_pv(ss, ply);
+
if (value == value_mate_in(ply + 1))
ss[ply].mateKiller = move;
}
&& TM.available_thread_exists(threadID)
&& !AbortSearch
&& !TM.thread_should_stop(threadID)
- && TM.split(pos, ss, ply, &alpha, beta, &bestValue,
- depth, mateThreat, &moveCount, &mp, threadID, PvNode))
+ && TM.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
+ mateThreat, &moveCount, &mp, threadID, PvNode))
break;
}
// also don't need to store anything to the hash table here: This is taken
// care of after we return from the split point.
+ template <NodeType PvNode>
void sp_search(SplitPoint* sp, int threadID) {
assert(threadID >= 0 && threadID < TM.active_threads());
StateInfo st;
Move move;
Depth ext, newDepth;
- Value value, futilityValueScaled;
+ Value value;
+ Value futilityValueScaled; // NonPV specific
bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
int moveCount;
value = -VALUE_INFINITE;
lock_grab(&(sp->lock));
while ( sp->bestValue < sp->beta
- && !TM.thread_should_stop(threadID)
- && (move = sp->mp->get_next_move()) != MOVE_NONE)
+ && (move = sp->mp->get_next_move()) != MOVE_NONE
+ && !TM.thread_should_stop(threadID))
{
moveCount = ++sp->moves;
lock_release(&(sp->lock));
captureOrPromotion = pos.move_is_capture_or_promotion(move);
// Step 11. Decide the new search depth
- ext = extension<NonPV>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
+ ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
newDepth = sp->depth - OnePly + ext;
// Update current move
ss[sp->ply].currentMove = move;
- // Step 12. Futility pruning
- if ( !isCheck
+ // Step 12. Futility pruning (is omitted in PV nodes)
+ if ( !PvNode
+ && !isCheck
&& !dangerous
&& !captureOrPromotion
&& !move_is_castle(move))
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
- ss[sp->ply].reduction = reduction<NonPV>(sp->depth, moveCount);
- if (ss[sp->ply].reduction)
- {
- value = -search<NonPV>(pos, ss, -(sp->alpha+1), -(sp->alpha), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
- doFullDepthSearch = (value >= sp->beta && !TM.thread_should_stop(threadID));
- }
- }
-
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- ss[sp->ply].reduction = Depth(0);
- value = -search<NonPV>(pos, ss, -(sp->alpha+1), -(sp->alpha), newDepth, sp->ply+1, true, threadID);
- }
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- // Step 17. Check for new best move
- lock_grab(&(sp->lock));
-
- if (value > sp->bestValue && !TM.thread_should_stop(threadID))
- {
- sp->bestValue = value;
- if (sp->bestValue >= sp->beta)
- {
- sp->stopRequest = true;
- sp_update_pv(sp->parentSstack, ss, sp->ply);
- }
- }
- }
-
- /* Here we have the lock still grabbed */
-
- sp->slaves[threadID] = 0;
- sp->cpus--;
-
- 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 < TM.active_threads());
- assert(TM.active_threads() > 1);
-
- StateInfo st;
- Move move;
- Depth ext, newDepth;
- Value value;
- bool moveIsCheck, captureOrPromotion, dangerous;
- int moveCount;
- value = -VALUE_INFINITE;
-
- Position pos(*sp->pos);
- CheckInfo ci(pos);
- SearchStack* ss = sp->sstack[threadID];
-
- // Step 10. Loop through moves
- // Loop through all legal moves until no moves remain or a beta cutoff occurs
- lock_grab(&(sp->lock));
-
- while ( sp->alpha < sp->beta
- && !TM.thread_should_stop(threadID)
- && (move = sp->mp->get_next_move()) != MOVE_NONE)
- {
- moveCount = ++sp->moves;
- lock_release(&(sp->lock));
-
- assert(move_is_ok(move));
-
- moveIsCheck = pos.move_is_check(move, ci);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- // Step 11. Decide the new search depth
- ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
- newDepth = sp->depth - OnePly + ext;
-
- // Update current move
- ss[sp->ply].currentMove = move;
-
- // Step 12. Futility pruning (is omitted in PV nodes)
-
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Step 14. Reduced search
- // if the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
-
- if ( !dangerous
- && !captureOrPromotion
- && !move_is_castle(move)
- && !move_is_killer(move, ss[sp->ply]))
- {
- ss[sp->ply].reduction = reduction<PV>(sp->depth, moveCount);
+ ss[sp->ply].reduction = reduction<PvNode>(sp->depth, moveCount);
if (ss[sp->ply].reduction)
{
Value localAlpha = sp->alpha;
value = -search<NonPV>(pos, ss, -(localAlpha+1), -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
- doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID));
+ doFullDepthSearch = (value > localAlpha);
}
}
// Step 15. Full depth search
if (doFullDepthSearch)
{
- Value localAlpha = sp->alpha;
ss[sp->ply].reduction = Depth(0);
+ Value localAlpha = sp->alpha;
value = -search<NonPV>(pos, ss, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1, true, threadID);
- if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID))
- {
- // If another thread has failed high then sp->alpha has been increased
- // to be higher or equal then beta, if so, avoid to start a PV search.
- localAlpha = sp->alpha;
- if (localAlpha < sp->beta)
- value = -search<PV>(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, false, threadID);
- }
+ if (PvNode && value > localAlpha && value < sp->beta)
+ value = -search<PV>(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, false, threadID);
}
// Step 16. Undo move
if (value > sp->bestValue && !TM.thread_should_stop(threadID))
{
sp->bestValue = value;
- if (value > sp->alpha)
+
+ if (sp->bestValue > sp->alpha)
{
- // Ask threads to stop before to modify sp->alpha
- if (value >= sp->beta)
+ if (!PvNode || value >= sp->beta)
sp->stopRequest = true;
- sp->alpha = value;
+ if (PvNode && value < sp->beta) // This guarantees that always: sp->alpha < sp->beta
+ sp->alpha = value;
sp_update_pv(sp->parentSstack, ss, sp->ply);
- if (value == value_mate_in(sp->ply + 1))
- ss[sp->ply].mateKiller = move;
}
}
}
/* Here we have the lock still grabbed */
sp->slaves[threadID] = 0;
- sp->cpus--;
lock_release(&(sp->lock));
}
-
// init_node() is called at the beginning of all the search functions
// (search() qsearch(), and so on) and initializes the
// search stack object corresponding to the current node. Once every
ss[ply + 2].initKillers();
}
-
// update_pv() is called whenever a search returns a value > alpha.
// It updates the PV in the SearchStack object corresponding to the
// current node.
threads[threadID].state = THREAD_SEARCHING;
if (threads[threadID].splitPoint->pvNode)
- sp_search_pv(threads[threadID].splitPoint, threadID);
+ sp_search<PV>(threads[threadID].splitPoint, threadID);
else
- sp_search(threads[threadID].splitPoint, threadID);
+ sp_search<NonPV>(threads[threadID].splitPoint, threadID);
assert(threads[threadID].state == THREAD_SEARCHING);
threads[threadID].state = THREAD_AVAILABLE;
}
- // If this thread is the master of a split point and all threads have
+ // If this thread is the master of a split point and all slaves have
// finished their work at this split point, return from the idle loop.
- if (sp && sp->cpus == 0)
+ int i = 0;
+ for ( ; sp && i < ActiveThreads && !sp->slaves[i]; i++) {}
+
+ if (i == ActiveThreads)
{
- // Because sp->cpus is decremented under lock protection,
- // be sure sp->lock has been released before to proceed.
+ // Because sp->slaves[] is reset under lock protection,
+ // be sure sp->lock has been released before to return.
lock_grab(&(sp->lock));
lock_release(&(sp->lock));
// 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 ThreadsManager::split(const Position& p, SearchStack* sstck, int ply,
- Value* alpha, const Value beta, Value* bestValue,
- Depth depth, bool mateThreat, int* moves, MovePicker* mp, int master, bool pvNode) {
+ // to instantly leave their idle loops and call sp_search(). When all
+ // threads have returned from sp_search() then split() returns true.
+ template <bool Fake>
+ bool ThreadsManager::split(const Position& p, SearchStack* sstck, int ply, Value* alpha,
+ const Value beta, Value* bestValue, Depth depth, bool mateThreat,
+ int* moves, MovePicker* mp, int master, bool pvNode) {
assert(p.is_ok());
assert(sstck != NULL);
assert(ply >= 0 && ply < PLY_MAX);
assert(*bestValue >= -VALUE_INFINITE);
- assert( ( pvNode && *bestValue <= *alpha)
- || (!pvNode && *bestValue < beta ));
- assert(!pvNode || *alpha < beta);
+ assert(*bestValue <= *alpha);
+ assert(*alpha < beta);
assert(beta <= VALUE_INFINITE);
assert(depth > Depth(0));
assert(master >= 0 && master < ActiveThreads);
splitPoint->master = master;
splitPoint->mp = mp;
splitPoint->moves = *moves;
- splitPoint->cpus = 1;
splitPoint->pos = &p;
splitPoint->parentSstack = sstck;
for (int i = 0; i < ActiveThreads; i++)
// If we are here it means we are not available
assert(threads[master].state != THREAD_AVAILABLE);
+ int workersCnt = 1; // At least the master is included
+
// Allocate available threads setting state to THREAD_BOOKED
- for (int i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint; i++)
+ for (int i = 0; !Fake && i < ActiveThreads && workersCnt < MaxThreadsPerSplitPoint; i++)
if (thread_is_available(i, master))
{
threads[i].state = THREAD_BOOKED;
threads[i].splitPoint = splitPoint;
splitPoint->slaves[i] = 1;
- splitPoint->cpus++;
+ workersCnt++;
}
- assert(splitPoint->cpus > 1);
+ assert(Fake || workersCnt > 1);
// We can release the lock because slave threads are already booked and master is not available
lock_release(&MPLock);
// which it will instantly launch a search, because its state is
// THREAD_WORKISWAITING. 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).
+ // loop when all threads have finished their work at this split point.
idle_loop(master, splitPoint);
// We have returned from the idle loop, which means that all threads are
projects / stockfish / blobdiff