X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fthread.cpp;h=30177a3915a84c9245644d779ca6fe0d99bc5a2b;hb=HEAD;hp=b79675f7c09dee12b68382691daab63db4a435b6;hpb=42b48b08e81b55e385e55b3074b7c59d81809a45;p=stockfish

diff --git a/src/thread.cpp b/src/thread.cpp
index b79675f7..b5d51594 100644
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -1,7 +1,6 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
-  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2004-2024 The Stockfish developers (see AUTHORS file)
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -17,369 +16,395 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <algorithm> // For std::count
+#include "thread.h"
+
+#include <algorithm>
 #include <cassert>
+#include <deque>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <utility>
 
 #include "movegen.h"
 #include "search.h"
-#include "thread.h"
+#include "syzygy/tbprobe.h"
+#include "timeman.h"
+#include "types.h"
 #include "uci.h"
-
-using namespace Search;
-
-ThreadPool Threads; // Global object
-
-extern void check_time();
-
-namespace {
-
- // start_routine() is the C function which is called when a new thread
- // is launched. It is a wrapper to the virtual function idle_loop().
-
- extern "C" { long start_routine(ThreadBase* th) { th->idle_loop(); return 0; } }
-
-
- // Helpers to launch a thread after creation and joining before delete. Must be
- // outside Thread c'tor and d'tor because the object must be fully initialized
- // when start_routine (and hence virtual idle_loop) is called and when joining.
-
- template<typename T> T* new_thread() {
-   T* th = new T();
-   thread_create(th->handle, start_routine, th); // Will go to sleep
-   return th;
- }
-
- void delete_thread(ThreadBase* th) {
-
-   th->mutex.lock();
-   th->exit = true; // Search must be already finished
-   th->mutex.unlock();
-
-   th->notify_one();
-   thread_join(th->handle); // Wait for thread termination
-   delete th;
- }
-
+#include "ucioption.h"
+
+namespace Stockfish {
+
+// Constructor launches the thread and waits until it goes to sleep
+// in idle_loop(). Note that 'searching' and 'exit' should be already set.
+Thread::Thread(Search::SharedState&                    sharedState,
+               std::unique_ptr<Search::ISearchManager> sm,
+               size_t                                  n,
+               OptionalThreadToNumaNodeBinder          binder) :
+    idx(n),
+    nthreads(sharedState.options["Threads"]),
+    stdThread(&Thread::idle_loop, this) {
+
+    wait_for_search_finished();
+
+    run_custom_job([this, &binder, &sharedState, &sm, n]() {
+        // Use the binder to [maybe] bind the threads to a NUMA node before doing
+        // the Worker allocation. Ideally we would also allocate the SearchManager
+        // here, but that's minor.
+        this->numaAccessToken = binder();
+        this->worker =
+          std::make_unique<Search::Worker>(sharedState, std::move(sm), n, this->numaAccessToken);
+    });
+
+    wait_for_search_finished();
 }
 
 
-// ThreadBase::notify_one() wakes up the thread when there is some work to do
+// Destructor wakes up the thread in idle_loop() and waits
+// for its termination. Thread should be already waiting.
+Thread::~Thread() {
 
-void ThreadBase::notify_one() {
+    assert(!searching);
 
-  mutex.lock();
-  sleepCondition.notify_one();
-  mutex.unlock();
+    exit = true;
+    start_searching();
+    stdThread.join();
 }
 
+// Wakes up the thread that will start the search
+void Thread::start_searching() {
+    assert(worker != nullptr);
+    run_custom_job([this]() { worker->start_searching(); });
+}
 
-// ThreadBase::wait_for() set the thread to sleep until 'condition' turns true
+// Clears the histories for the thread worker (usually before a new game)
+void Thread::clear_worker() {
+    assert(worker != nullptr);
+    run_custom_job([this]() { worker->clear(); });
+}
 
-void ThreadBase::wait_for(volatile const bool& condition) {
+// Blocks on the condition variable until the thread has finished searching
+void Thread::wait_for_search_finished() {
 
-  mutex.lock();
-  while (!condition) sleepCondition.wait(mutex);
-  mutex.unlock();
+    std::unique_lock<std::mutex> lk(mutex);
+    cv.wait(lk, [&] { return !searching; });
 }
 
+// Launching a function in the thread
+void Thread::run_custom_job(std::function<void()> f) {
+    {
+        std::unique_lock<std::mutex> lk(mutex);
+        cv.wait(lk, [&] { return !searching; });
+        jobFunc   = std::move(f);
+        searching = true;
+    }
+    cv.notify_one();
+}
 
-// Thread c'tor makes some init but does not launch any execution thread that
-// will be started only when c'tor returns.
+void Thread::ensure_network_replicated() { worker->ensure_network_replicated(); }
 
-Thread::Thread() /* : splitPoints() */ { // Value-initialization bug in MSVC
+// Thread gets parked here, blocked on the condition variable
+// when the thread has no work to do.
 
-  searching = false;
-  maxPly = splitPointsSize = 0;
-  activeSplitPoint = NULL;
-  activePosition = NULL;
-  idx = Threads.size(); // Starts from 0
-}
+void Thread::idle_loop() {
+    while (true)
+    {
+        std::unique_lock<std::mutex> lk(mutex);
+        searching = false;
+        cv.notify_one();  // Wake up anyone waiting for search finished
+        cv.wait(lk, [&] { return searching; });
 
+        if (exit)
+            return;
 
-// Thread::cutoff_occurred() checks whether a beta cutoff has occurred in the
-// current active split point, or in some ancestor of the split point.
+        std::function<void()> job = std::move(jobFunc);
+        jobFunc                   = nullptr;
 
-bool Thread::cutoff_occurred() const {
+        lk.unlock();
 
-  for (SplitPoint* sp = activeSplitPoint; sp; sp = sp->parentSplitPoint)
-      if (sp->cutoff)
-          return true;
+        if (job)
+            job();
+    }
+}
 
-  return false;
+Search::SearchManager* ThreadPool::main_manager() { return main_thread()->worker->main_manager(); }
+
+uint64_t ThreadPool::nodes_searched() const { return accumulate(&Search::Worker::nodes); }
+uint64_t ThreadPool::tb_hits() const { return accumulate(&Search::Worker::tbHits); }
+
+// Creates/destroys threads to match the requested number.
+// Created and launched threads will immediately go to sleep in idle_loop.
+// Upon resizing, threads are recreated to allow for binding if necessary.
+void ThreadPool::set(const NumaConfig&                           numaConfig,
+                     Search::SharedState                         sharedState,
+                     const Search::SearchManager::UpdateContext& updateContext) {
+
+    if (threads.size() > 0)  // destroy any existing thread(s)
+    {
+        main_thread()->wait_for_search_finished();
+
+        threads.clear();
+
+        boundThreadToNumaNode.clear();
+    }
+
+    const size_t requested = sharedState.options["Threads"];
+
+    if (requested > 0)  // create new thread(s)
+    {
+        // Binding threads may be problematic when there's multiple NUMA nodes and
+        // multiple Stockfish instances running. In particular, if each instance
+        // runs a single thread then they would all be mapped to the first NUMA node.
+        // This is undesirable, and so the default behaviour (i.e. when the user does not
+        // change the NumaConfig UCI setting) is to not bind the threads to processors
+        // unless we know for sure that we span NUMA nodes and replication is required.
+        const std::string numaPolicy(sharedState.options["NumaPolicy"]);
+        const bool        doBindThreads = [&]() {
+            if (numaPolicy == "none")
+                return false;
+
+            if (numaPolicy == "auto")
+                return numaConfig.suggests_binding_threads(requested);
+
+            // numaPolicy == "system", or explicitly set by the user
+            return true;
+        }();
+
+        boundThreadToNumaNode = doBindThreads
+                                ? numaConfig.distribute_threads_among_numa_nodes(requested)
+                                : std::vector<NumaIndex>{};
+
+        while (threads.size() < requested)
+        {
+            const size_t    threadId = threads.size();
+            const NumaIndex numaId   = doBindThreads ? boundThreadToNumaNode[threadId] : 0;
+            auto            manager  = threadId == 0 ? std::unique_ptr<Search::ISearchManager>(
+                                             std::make_unique<Search::SearchManager>(updateContext))
+                                                     : std::make_unique<Search::NullSearchManager>();
+
+            // When not binding threads we want to force all access to happen
+            // from the same NUMA node, because in case of NUMA replicated memory
+            // accesses we don't want to trash cache in case the threads get scheduled
+            // on the same NUMA node.
+            auto binder = doBindThreads ? OptionalThreadToNumaNodeBinder(numaConfig, numaId)
+                                        : OptionalThreadToNumaNodeBinder(numaId);
+
+            threads.emplace_back(
+              std::make_unique<Thread>(sharedState, std::move(manager), threadId, binder));
+        }
+
+        clear();
+
+        main_thread()->wait_for_search_finished();
+    }
 }
 
 
-// Thread::available_to() checks whether the thread is available to help the
-// thread 'master' at a split point. An obvious requirement is that thread must
-// be idle. With more than two threads, this is not sufficient: If the thread is
-// the master of some split point, it is only available as a slave to the slaves
-// which are busy searching the split point at the top of slave's split point
-// stack (the "helpful master concept" in YBWC terminology).
+// Sets threadPool data to initial values
+void ThreadPool::clear() {
+    if (threads.size() == 0)
+        return;
 
-bool Thread::available_to(const Thread* master) const {
+    for (auto&& th : threads)
+        th->clear_worker();
 
-  if (searching)
-      return false;
+    for (auto&& th : threads)
+        th->wait_for_search_finished();
 
-  // Make a local copy to be sure it doesn't become zero under our feet while
-  // testing next condition and so leading to an out of bounds access.
-  const int size = splitPointsSize;
+    // These two affect the time taken on the first move of a game:
+    main_manager()->bestPreviousAverageScore = VALUE_INFINITE;
+    main_manager()->previousTimeReduction    = 0.85;
 
-  // No split points means that the thread is available as a slave for any
-  // other thread otherwise apply the "helpful master" concept if possible.
-  return !size || splitPoints[size - 1].slavesMask.test(master->idx);
+    main_manager()->callsCnt           = 0;
+    main_manager()->bestPreviousScore  = VALUE_INFINITE;
+    main_manager()->originalTimeAdjust = -1;
+    main_manager()->tm.clear();
 }
 
-
-// Thread::split() does the actual work of distributing the work at a node between
-// several available threads. If it does not succeed in splitting the node
-// (because no idle threads are available), the function immediately returns.
-// If splitting is possible, a SplitPoint object is initialized with all the
-// data that must be copied to the helper threads and then helper threads are
-// informed that they have been assigned work. This will cause them to instantly
-// leave their idle loops and call search(). When all threads have returned from
-// search() then split() returns.
-
-void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bestValue,
-                   Move* bestMove, Depth depth, int moveCount,
-                   MovePicker* movePicker, int nodeType, bool cutNode) {
-
-  assert(searching);
-  assert(-VALUE_INFINITE < *bestValue && *bestValue <= alpha && alpha < beta && beta <= VALUE_INFINITE);
-  assert(depth >= Threads.minimumSplitDepth);
-  assert(splitPointsSize < MAX_SPLITPOINTS_PER_THREAD);
-
-  // Pick and init the next available split point
-  SplitPoint& sp = splitPoints[splitPointsSize];
-
-  sp.masterThread = this;
-  sp.parentSplitPoint = activeSplitPoint;
-  sp.slavesMask = 0, sp.slavesMask.set(idx);
-  sp.depth = depth;
-  sp.bestValue = *bestValue;
-  sp.bestMove = *bestMove;
-  sp.alpha = alpha;
-  sp.beta = beta;
-  sp.nodeType = nodeType;
-  sp.cutNode = cutNode;
-  sp.movePicker = movePicker;
-  sp.moveCount = moveCount;
-  sp.pos = &pos;
-  sp.nodes = 0;
-  sp.cutoff = false;
-  sp.ss = ss;
-
-  // Try to allocate available threads and ask them to start searching setting
-  // 'searching' flag. This must be done under lock protection to avoid concurrent
-  // allocation of the same slave by another master.
-  Threads.mutex.lock();
-  sp.mutex.lock();
-
-  sp.allSlavesSearching = true; // Must be set under lock protection
-  ++splitPointsSize;
-  activeSplitPoint = &sp;
-  activePosition = NULL;
-
-  Thread* slave;
-
-  while ((slave = Threads.available_slave(this)) != NULL)
-  {
-      sp.slavesMask.set(slave->idx);
-      slave->activeSplitPoint = &sp;
-      slave->searching = true; // Slave leaves idle_loop()
-      slave->notify_one(); // Could be sleeping
-  }
-
-  // Everything is set up. The master thread enters the idle loop, from which
-  // it will instantly launch a search, because its 'searching' flag is set.
-  // The thread will return from the idle loop when all slaves have finished
-  // their work at this split point.
-  sp.mutex.unlock();
-  Threads.mutex.unlock();
-
-  Thread::idle_loop(); // Force a call to base class idle_loop()
-
-  // In the helpful master concept, a master can help only a sub-tree of its
-  // split point and because everything is finished here, it's not possible
-  // for the master to be booked.
-  assert(!searching);
-  assert(!activePosition);
-
-  // We have returned from the idle loop, which means that all threads are
-  // finished. Note that setting 'searching' and decreasing splitPointsSize must
-  // be done under lock protection to avoid a race with Thread::available_to().
-  Threads.mutex.lock();
-  sp.mutex.lock();
-
-  searching = true;
-  --splitPointsSize;
-  activeSplitPoint = sp.parentSplitPoint;
-  activePosition = &pos;
-  pos.set_nodes_searched(pos.nodes_searched() + sp.nodes);
-  *bestMove = sp.bestMove;
-  *bestValue = sp.bestValue;
-
-  sp.mutex.unlock();
-  Threads.mutex.unlock();
+void ThreadPool::run_on_thread(size_t threadId, std::function<void()> f) {
+    assert(threads.size() > threadId);
+    threads[threadId]->run_custom_job(std::move(f));
 }
 
+void ThreadPool::wait_on_thread(size_t threadId) {
+    assert(threads.size() > threadId);
+    threads[threadId]->wait_for_search_finished();
+}
 
-// TimerThread::idle_loop() is where the timer thread waits Resolution milliseconds
-// and then calls check_time(). When not searching, thread sleeps until it's woken up.
-
-void TimerThread::idle_loop() {
+size_t ThreadPool::num_threads() const { return threads.size(); }
 
-  while (!exit)
-  {
-      mutex.lock();
 
-      if (!exit)
-          sleepCondition.wait_for(mutex, run ? Resolution : INT_MAX);
+// Wakes up main thread waiting in idle_loop() and returns immediately.
+// Main thread will wake up other threads and start the search.
+void ThreadPool::start_thinking(const OptionsMap&  options,
+                                Position&          pos,
+                                StateListPtr&      states,
+                                Search::LimitsType limits) {
 
-      mutex.unlock();
+    main_thread()->wait_for_search_finished();
 
-      if (run)
-          check_time();
-  }
-}
+    main_manager()->stopOnPonderhit = stop = abortedSearch = false;
+    main_manager()->ponder                                 = limits.ponderMode;
 
+    increaseDepth = true;
 
-// MainThread::idle_loop() is where the main thread is parked waiting to be started
-// when there is a new search. The main thread will launch all the slave threads.
+    Search::RootMoves rootMoves;
+    const auto        legalmoves = MoveList<LEGAL>(pos);
 
-void MainThread::idle_loop() {
+    for (const auto& uciMove : limits.searchmoves)
+    {
+        auto move = UCIEngine::to_move(pos, uciMove);
 
-  while (!exit)
-  {
-      mutex.lock();
+        if (std::find(legalmoves.begin(), legalmoves.end(), move) != legalmoves.end())
+            rootMoves.emplace_back(move);
+    }
 
-      thinking = false;
+    if (rootMoves.empty())
+        for (const auto& m : legalmoves)
+            rootMoves.emplace_back(m);
 
-      while (!thinking && !exit)
-      {
-          Threads.sleepCondition.notify_one(); // Wake up the UI thread if needed
-          sleepCondition.wait(mutex);
-      }
+    Tablebases::Config tbConfig = Tablebases::rank_root_moves(options, pos, rootMoves);
 
-      mutex.unlock();
+    // After ownership transfer 'states' becomes empty, so if we stop the search
+    // and call 'go' again without setting a new position states.get() == nullptr.
+    assert(states.get() || setupStates.get());
 
-      if (!exit)
-      {
-          searching = true;
+    if (states.get())
+        setupStates = std::move(states);  // Ownership transfer, states is now empty
 
-          Search::think();
+    // We use Position::set() to set root position across threads. But there are
+    // some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
+    // be deduced from a fen string, so set() clears them and they are set from
+    // setupStates->back() later. The rootState is per thread, earlier states are
+    // shared since they are read-only.
+    for (auto&& th : threads)
+    {
+        th->run_custom_job([&]() {
+            th->worker->limits = limits;
+            th->worker->nodes = th->worker->tbHits = th->worker->nmpMinPly =
+              th->worker->bestMoveChanges          = 0;
+            th->worker->rootDepth = th->worker->completedDepth = 0;
+            th->worker->rootMoves                              = rootMoves;
+            th->worker->rootPos.set(pos.fen(), pos.is_chess960(), &th->worker->rootState);
+            th->worker->rootState = setupStates->back();
+            th->worker->tbConfig  = tbConfig;
+        });
+    }
 
-          assert(searching);
+    for (auto&& th : threads)
+        th->wait_for_search_finished();
 
-          searching = false;
-      }
-  }
+    main_thread()->start_searching();
 }
 
-
-// ThreadPool::init() is called at startup to create and launch requested threads,
-// that will go immediately to sleep. We cannot use a c'tor because Threads is a
-// static object and we need a fully initialized engine at this point due to
-// allocation of Endgames in Thread c'tor.
-
-void ThreadPool::init() {
-
-  timer = new_thread<TimerThread>();
-  push_back(new_thread<MainThread>());
-  read_uci_options();
+Thread* ThreadPool::get_best_thread() const {
+
+    Thread* bestThread = threads.front().get();
+    Value   minScore   = VALUE_NONE;
+
+    std::unordered_map<Move, int64_t, Move::MoveHash> votes(
+      2 * std::min(size(), bestThread->worker->rootMoves.size()));
+
+    // Find the minimum score of all threads
+    for (auto&& th : threads)
+        minScore = std::min(minScore, th->worker->rootMoves[0].score);
+
+    // Vote according to score and depth, and select the best thread
+    auto thread_voting_value = [minScore](Thread* th) {
+        return (th->worker->rootMoves[0].score - minScore + 14) * int(th->worker->completedDepth);
+    };
+
+    for (auto&& th : threads)
+        votes[th->worker->rootMoves[0].pv[0]] += thread_voting_value(th.get());
+
+    for (auto&& th : threads)
+    {
+        const auto bestThreadScore = bestThread->worker->rootMoves[0].score;
+        const auto newThreadScore  = th->worker->rootMoves[0].score;
+
+        const auto& bestThreadPV = bestThread->worker->rootMoves[0].pv;
+        const auto& newThreadPV  = th->worker->rootMoves[0].pv;
+
+        const auto bestThreadMoveVote = votes[bestThreadPV[0]];
+        const auto newThreadMoveVote  = votes[newThreadPV[0]];
+
+        const bool bestThreadInProvenWin = bestThreadScore >= VALUE_TB_WIN_IN_MAX_PLY;
+        const bool newThreadInProvenWin  = newThreadScore >= VALUE_TB_WIN_IN_MAX_PLY;
+
+        const bool bestThreadInProvenLoss =
+          bestThreadScore != -VALUE_INFINITE && bestThreadScore <= VALUE_TB_LOSS_IN_MAX_PLY;
+        const bool newThreadInProvenLoss =
+          newThreadScore != -VALUE_INFINITE && newThreadScore <= VALUE_TB_LOSS_IN_MAX_PLY;
+
+        // We make sure not to pick a thread with truncated principal variation
+        const bool betterVotingValue =
+          thread_voting_value(th.get()) * int(newThreadPV.size() > 2)
+          > thread_voting_value(bestThread) * int(bestThreadPV.size() > 2);
+
+        if (bestThreadInProvenWin)
+        {
+            // Make sure we pick the shortest mate / TB conversion
+            if (newThreadScore > bestThreadScore)
+                bestThread = th.get();
+        }
+        else if (bestThreadInProvenLoss)
+        {
+            // Make sure we pick the shortest mated / TB conversion
+            if (newThreadInProvenLoss && newThreadScore < bestThreadScore)
+                bestThread = th.get();
+        }
+        else if (newThreadInProvenWin || newThreadInProvenLoss
+                 || (newThreadScore > VALUE_TB_LOSS_IN_MAX_PLY
+                     && (newThreadMoveVote > bestThreadMoveVote
+                         || (newThreadMoveVote == bestThreadMoveVote && betterVotingValue))))
+            bestThread = th.get();
+    }
+
+    return bestThread;
 }
 
 
-// ThreadPool::exit() terminates the threads before the program exits. Cannot be
-// done in d'tor because threads must be terminated before freeing us.
-
-void ThreadPool::exit() {
+// Start non-main threads.
+// Will be invoked by main thread after it has started searching.
+void ThreadPool::start_searching() {
 
-  delete_thread(timer); // As first because check_time() accesses threads data
-
-  for (iterator it = begin(); it != end(); ++it)
-      delete_thread(*it);
+    for (auto&& th : threads)
+        if (th != threads.front())
+            th->start_searching();
 }
 
 
-// ThreadPool::read_uci_options() updates internal threads parameters from the
-// corresponding UCI options and creates/destroys threads to match the requested
-// number. Thread objects are dynamically allocated to avoid creating all possible
-// threads in advance (which include pawns and material tables), even if only a
-// few are to be used.
-
-void ThreadPool::read_uci_options() {
-
-  minimumSplitDepth = Options["Min Split Depth"] * ONE_PLY;
-  size_t requested  = Options["Threads"];
-
-  assert(requested > 0);
-
-  // If zero (default) then set best minimum split depth automatically
-  if (!minimumSplitDepth)
-      minimumSplitDepth = requested < 8 ? 4 * ONE_PLY : 7 * ONE_PLY;
-
-  while (size() < requested)
-      push_back(new_thread<Thread>());
+// Wait for non-main threads
+void ThreadPool::wait_for_search_finished() const {
 
-  while (size() > requested)
-  {
-      delete_thread(back());
-      pop_back();
-  }
+    for (auto&& th : threads)
+        if (th != threads.front())
+            th->wait_for_search_finished();
 }
 
+std::vector<size_t> ThreadPool::get_bound_thread_count_by_numa_node() const {
+    std::vector<size_t> counts;
 
-// ThreadPool::available_slave() tries to find an idle thread which is available
-// as a slave for the thread 'master'.
+    if (!boundThreadToNumaNode.empty())
+    {
+        NumaIndex highestNumaNode = 0;
+        for (NumaIndex n : boundThreadToNumaNode)
+            if (n > highestNumaNode)
+                highestNumaNode = n;
 
-Thread* ThreadPool::available_slave(const Thread* master) const {
+        counts.resize(highestNumaNode + 1, 0);
 
-  for (const_iterator it = begin(); it != end(); ++it)
-      if ((*it)->available_to(master))
-          return *it;
+        for (NumaIndex n : boundThreadToNumaNode)
+            counts[n] += 1;
+    }
 
-  return NULL;
+    return counts;
 }
 
-
-// ThreadPool::wait_for_think_finished() waits for main thread to finish the search
-
-void ThreadPool::wait_for_think_finished() {
-
-  MainThread* th = main();
-  th->mutex.lock();
-  while (th->thinking) sleepCondition.wait(th->mutex);
-  th->mutex.unlock();
+void ThreadPool::ensure_network_replicated() {
+    for (auto&& th : threads)
+        th->ensure_network_replicated();
 }
 
-
-// ThreadPool::start_thinking() wakes up the main thread sleeping in
-// MainThread::idle_loop() and starts a new search, then returns immediately.
-
-void ThreadPool::start_thinking(const Position& pos, const LimitsType& limits,
-                                StateStackPtr& states) {
-  wait_for_think_finished();
-
-  SearchTime = Time::now(); // As early as possible
-
-  Signals.stopOnPonderhit = Signals.firstRootMove = false;
-  Signals.stop = Signals.failedLowAtRoot = false;
-
-  RootMoves.clear();
-  RootPos = pos;
-  Limits = limits;
-  if (states.get()) // If we don't set a new position, preserve current state
-  {
-      SetupStates = states; // Ownership transfer here
-      assert(!states.get());
-  }
-
-  for (MoveList<LEGAL> it(pos); *it; ++it)
-      if (   limits.searchmoves.empty()
-          || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), *it))
-          RootMoves.push_back(RootMove(*it));
-
-  main()->thinking = true;
-  main()->notify_one(); // Starts main thread
-}
+}  // namespace Stockfish