Derive ThreadPool from std::vector

Prefer sub-classing to composition in this case.

No functional change.

src/search.cpp

@@ -229,22 +229,22 @@ void Search::think() {
 
   // Reset the threads, still sleeping: will be wake up at split time
   for (size_t i = 0; i < Threads.size(); i++)
-      Threads[i].maxPly = 0;
+      Threads[i]->maxPly = 0;
 
   Threads.sleepWhileIdle = Options["Use Sleeping Threads"];
 
   // Set best timer interval to avoid lagging under time pressure. Timer is
   // used to check for remaining available thinking time.
-  Threads.timer_thread()->msec =
+  Threads.timer->msec =
   Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) :
                   Limits.nodes ? 2 * TimerResolution
                                : 100;
 
-  Threads.timer_thread()->notify_one(); // Wake up the recurring timer
+  Threads.timer->notify_one(); // Wake up the recurring timer
 
   id_loop(RootPos); // Let's start searching !
 
-  Threads.timer_thread()->msec = 0; // Stop the timer
+  Threads.timer->msec = 0; // Stop the timer
   Threads.sleepWhileIdle = true; // Send idle threads to sleep
 
   if (Options["Use Search Log"])
@@ -1513,8 +1513,8 @@ split_point_start: // At split points actual search starts from here
     int selDepth = 0;
 
     for (size_t i = 0; i < Threads.size(); i++)
-        if (Threads[i].maxPly > selDepth)
-            selDepth = Threads[i].maxPly;
+        if (Threads[i]->maxPly > selDepth)
+            selDepth = Threads[i]->maxPly;
 
     for (size_t i = 0; i < uciPVSize; i++)
     {
@@ -1744,9 +1744,9 @@ void check_time() {
       // Loop across all split points and sum accumulated SplitPoint nodes plus
       // all the currently active slaves positions.
       for (size_t i = 0; i < Threads.size(); i++)
-          for (int j = 0; j < Threads[i].splitPointsSize; j++)
+          for (int j = 0; j < Threads[i]->splitPointsSize; j++)
           {
-              SplitPoint& sp = Threads[i].splitPoints[j];
+              SplitPoint& sp = Threads[i]->splitPoints[j];
 
               sp.mutex.lock();
 

src/thread.cpp

@@ -186,7 +186,7 @@ void ThreadPool::init() {
 
   sleepWhileIdle = true;
   timer = new TimerThread();
-  threads.push_back(new MainThread());
+  push_back(new MainThread());
   read_uci_options();
 }
 
@@ -197,8 +197,8 @@ void ThreadPool::exit() {
 
   delete timer; // As first because check_time() accesses threads data
 
-  for (size_t i = 0; i < threads.size(); i++)
-      delete threads[i];
+  for (iterator it = begin(); it != end(); ++it)
+      delete *it;
 }
 
 
@@ -215,13 +215,13 @@ void ThreadPool::read_uci_options() {
 
   assert(requested > 0);
 
-  while (threads.size() < requested)
-      threads.push_back(new Thread());
+  while (size() < requested)
+      push_back(new Thread());
 
-  while (threads.size() > requested)
+  while (size() > requested)
   {
-      delete threads.back();
-      threads.pop_back();
+      delete back();
+      pop_back();
   }
 }
 
@@ -231,8 +231,8 @@ void ThreadPool::read_uci_options() {
 
 bool ThreadPool::slave_available(Thread* master) const {
 
-  for (size_t i = 0; i < threads.size(); i++)
-      if (threads[i]->is_available_to(master))
+  for (const_iterator it = begin(); it != end(); ++it)
+      if ((*it)->is_available_to(master))
           return true;
 
   return false;
@@ -290,16 +290,20 @@ Value Thread::split(Position& pos, Stack* ss, Value alpha, Value beta,
   splitPointsSize++;
   activeSplitPoint = &sp;
 
-  size_t slavesCnt = 1; // Master is always included
+  size_t slavesCnt = 1; // This thread is always included
 
-  for (size_t i = 0; i < Threads.size() && !Fake; ++i)
-      if (Threads[i].is_available_to(this) && ++slavesCnt <= Threads.maxThreadsPerSplitPoint)
+  for (ThreadPool::iterator it = Threads.begin(); it != Threads.end() && !Fake; ++it)
+  {
+      Thread* slave = *it;
+
+      if (slave->is_available_to(this) && ++slavesCnt <= Threads.maxThreadsPerSplitPoint)
       {
-          sp.slavesMask |= 1ULL << Threads[i].idx;
-          Threads[i].activeSplitPoint = &sp;
-          Threads[i].searching = true; // Slave leaves idle_loop()
-          Threads[i].notify_one(); // Could be sleeping
+          sp.slavesMask |= 1ULL << slave->idx;
+          slave->activeSplitPoint = &sp;
+          slave->searching = true; // Slave leaves idle_loop()
+          slave->notify_one(); // Could be sleeping
       }
+  }
 
   sp.mutex.unlock();
   Threads.mutex.unlock();

src/thread.h

@@ -138,21 +138,16 @@ struct TimerThread : public Thread {
 };
 
 
-/// ThreadPool class handles all the threads related stuff like init, starting,
+/// ThreadPool struct handles all the threads related stuff like init, starting,
 /// parking and, the most important, launching a slave thread at a split point.
 /// All the access to shared thread data is done through this class.
 
-class ThreadPool {
+struct ThreadPool : public std::vector<Thread*> {
 
-public:
   void init(); // No c'tor and d'tor, threads rely on globals that should
   void exit(); // be initialized and valid during the whole thread lifetime.
 
-  Thread& operator[](size_t id) { return *threads[id]; }
-  size_t size() const { return threads.size(); }
-  MainThread* main_thread() { return static_cast<MainThread*>(threads[0]); }
-  TimerThread* timer_thread() { return timer; }
-
+  MainThread* main_thread() { return static_cast<MainThread*>((*this)[0]); }
   void read_uci_options();
   bool slave_available(Thread* master) const;
   void wait_for_think_finished();
@@ -164,9 +159,6 @@ public:
   size_t maxThreadsPerSplitPoint;
   Mutex mutex;
   ConditionVariable sleepCondition;
-
-private:
-  std::vector<Thread*> threads;
   TimerThread* timer;
 };