Use std::vector<Thread*> to store threads

We store pointers instead of Thread objects because
Thread is not copy-constructible nor copy-assignable
and default ones are not suitable. So we cannot store
directly in a std::vector.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/evaluate.cpp

@@ -357,13 +357,12 @@ namespace {
 template<bool Trace>
 Value do_evaluate(const Position& pos, Value& margin) {
 
+  assert(!pos.in_check());
+
   EvalInfo ei;
   Value margins[2];
   Score score, mobilityWhite, mobilityBlack;
 
-  assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
-  assert(!pos.in_check());
-
   // Initialize score by reading the incrementally updated scores included
   // in the position object (material + piece square tables).
   score = pos.value();

src/search.cpp

@@ -310,8 +310,7 @@ void Search::think() {
   // We're ready to start searching. Call the iterative deepening loop function
   id_loop(pos);
 
-  // Stop timer and send all the slaves to sleep, if not already sleeping
-  Threads.set_timer(0);
+  Threads.set_timer(0); // Stop timer
   Threads.sleep();
 
   if (Options["Use Search Log"])

src/thread.cpp

@@ -53,13 +53,16 @@ namespace { extern "C" {
 } }
 
 
+// Thread c'tor creates and launches the OS thread, that will go immediately to
+// sleep.
+
 Thread::Thread(int id) {
 
-  threadID = id;
-  do_sleep = (id != 0); // Avoid a race with start_thinking()
   is_searching = do_exit = false;
   maxPly = splitPointsCnt = 0;
   curSplitPoint = NULL;
+  threadID = id;
+  do_sleep = (id != 0); // Avoid a race with start_thinking()
 
   lock_init(sleepLock);
   cond_init(sleepCond);
@@ -75,6 +78,8 @@ Thread::Thread(int id) {
 }
 
 
+// Thread d'tor will wait for thread termination before to return.
+
 Thread::~Thread() {
 
   assert(do_sleep);
@@ -205,42 +210,49 @@ bool Thread::is_available_to(int master) const {
 
 
 // read_uci_options() updates internal threads parameters from the corresponding
-// UCI options. It is called before to start a new search.
+// UCI options and creates/destroys threads to match the requested number. Thread
+// objects are dynamically allocated to avoid creating in advance all possible
+// threads, with included pawns and material tables, if only few are used.
 
 void ThreadsManager::read_uci_options() {
 
   maxThreadsPerSplitPoint = Options["Max Threads per Split Point"];
   minimumSplitDepth       = Options["Min Split Depth"] * ONE_PLY;
   useSleepingThreads      = Options["Use Sleeping Threads"];
-  activeThreads           = Options["Threads"];
+  int requested           = Options["Threads"];
 
-  // Dynamically allocate Thread object according to the number of
-  // active threads. This avoids preallocating memory for all possible
-  // threads if only few are used.
-  for (int i = 0; i < MAX_THREADS; i++)
-      if (i < activeThreads && !threads[i])
-          threads[i] = new Thread(i);
-      else if (i >= activeThreads && threads[i])
+  while (size() < requested)
+      threads.push_back(new Thread(size()));
+
+  while (size() > requested)
   {
-          delete threads[i];
-          threads[i] = NULL;
+      delete threads.back();
+      threads.pop_back();
   }
 }
 
 
+// wake_up() is called before a new search to start the threads that are waiting
+// on the sleep condition. If useSleepingThreads is set threads will be woken up
+// at split time.
+
 void ThreadsManager::wake_up() {
 
-  for (int i = 0; i < activeThreads; i++)
+  for (int i = 0; i < size(); i++)
   {
       threads[i]->do_sleep = false;
+
+      if (!useSleepingThreads)
           threads[i]->wake_up();
   }
 }
 
 
+// sleep() is called after the search to ask threads to wait on sleep condition
+
 void ThreadsManager::sleep() {
 
-  for (int i = 0; i < activeThreads; i++)
+  for (int i = 0; i < size(); i++)
       threads[i]->do_sleep = true;
 }
 
@@ -253,16 +265,15 @@ void ThreadsManager::init() {
     cond_init(sleepCond);
     lock_init(splitLock);
     timer = new Thread(MAX_THREADS);
-    read_uci_options(); // Creates at least main thread
+    read_uci_options(); // Creates at least the main thread
 }
 
 
-// exit() is called to cleanly terminate the threads when the program finishes
+// exit() is called to cleanly terminate the threads before the program finishes
 
 void ThreadsManager::exit() {
 
-  for (int i = 0; i < MAX_THREADS; i++)
-      if (threads[i])
+  for (int i = 0; i < size(); i++)
       delete threads[i];
 
   delete timer;
@@ -276,9 +287,9 @@ void ThreadsManager::exit() {
 
 bool ThreadsManager::available_slave_exists(int master) const {
 
-  assert(master >= 0 && master < activeThreads);
+  assert(master >= 0 && master < size());
 
-  for (int i = 0; i < activeThreads; i++)
+  for (int i = 0; i < size(); i++)
       if (threads[i]->is_available_to(master))
           return true;
 
@@ -305,8 +316,6 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
   assert(alpha < beta);
   assert(beta <= VALUE_INFINITE);
   assert(depth > DEPTH_ZERO);
-  assert(pos.thread() >= 0 && pos.thread() < activeThreads);
-  assert(activeThreads > 1);
 
   int master = pos.thread();
   Thread& masterThread = *threads[master];
@@ -345,7 +354,7 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
   lock_grab(sp->lock);
   lock_grab(splitLock);
 
-  for (int i = 0; i < activeThreads && !Fake; i++)
+  for (int i = 0; i < size() && !Fake; ++i)
       if (threads[i]->is_available_to(master))
       {
           sp->slavesMask |= 1ULL << i;
@@ -418,7 +427,7 @@ void ThreadsManager::set_timer(int msec) {
 
 void ThreadsManager::start_thinking(const Position& pos, const LimitsType& limits,
                                     const std::set<Move>& searchMoves, bool async) {
-  Thread& main = *threads[0];
+  Thread& main = *threads.front();
 
   lock_grab(main.sleepLock);
 
@@ -458,7 +467,7 @@ void ThreadsManager::start_thinking(const Position& pos, const LimitsType& limit
 
 void ThreadsManager::stop_thinking() {
 
-  Thread& main = *threads[0];
+  Thread& main = *threads.front();
 
   Search::Signals.stop = true;
 

src/thread.h

@@ -21,6 +21,7 @@
 #define THREAD_H_INCLUDED
 
 #include <set>
+#include <vector>
 
 #include "material.h"
 #include "movepick.h"
@@ -64,8 +65,12 @@ struct SplitPoint {
 /// tables so that once we get a pointer to an entry its life time is unlimited
 /// and we don't have to care about someone changing the entry under our feet.
 
-struct Thread {
+class Thread {
 
+  Thread(const Thread&);            // Only declared to disable the default ones
+  Thread& operator=(const Thread&); // that are not suitable in this case.
+
+public:
   Thread(int id);
   ~Thread();
 
@@ -103,13 +108,13 @@ class ThreadsManager {
      static storage duration are automatically set to zero before enter main()
   */
 public:
-  Thread& operator[](int threadID) { return *threads[threadID]; }
   void init();
   void exit();
 
+  Thread& operator[](int id) { return *threads[id]; }
   bool use_sleeping_threads() const { return useSleepingThreads; }
   int min_split_depth() const { return minimumSplitDepth; }
-  int size() const { return activeThreads; }
+  int size() const { return (int)threads.size(); }
 
   void wake_up();
   void sleep();
@@ -124,15 +129,14 @@ public:
   Value split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value bestValue, Move* bestMove,
               Depth depth, Move threatMove, int moveCount, MovePicker* mp, int nodeType);
 private:
-  friend struct Thread;
+  friend class Thread;
 
+  std::vector<Thread*> threads;
   Thread* timer;
-  Thread* threads[MAX_THREADS];
   Lock splitLock;
   WaitCondition sleepCond;
   Depth minimumSplitDepth;
   int maxThreadsPerSplitPoint;
-  int activeThreads;
   bool useSleepingThreads;
 };