Rework Thread hierarchy

Introduce ThreadBase struct that is search
agnostic and just handles low level stuff,
and derive all the other specialized classes
form here.

In particular TimerThread does not hinerits
anymore all the search related stuff from Thread.

Also some renaming while there.

Suggested by Steven Edwards

No functional change.

src/thread.cpp

@@ -34,7 +34,7 @@ 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(Thread* th) { th->idle_loop(); return 0; } }
+ 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
@@ -43,11 +43,11 @@ namespace {
 
  template<typename T> T* new_thread() {
    T* th = new T();
-   thread_create(th->handle, start_routine, th);
+   thread_create(th->handle, start_routine, th); // Will go to sleep
    return th;
  }
 
- void delete_thread(Thread* th) {
+ void delete_thread(ThreadBase* th) {
    th->exit = true; // Search must be already finished
    th->notify_one();
    thread_join(th->handle); // Wait for thread termination
@@ -57,12 +57,32 @@ namespace {
 }
 
 
-// Thread c'tor starts a newly-created thread of execution that will call
-// the the virtual function idle_loop(), going immediately to sleep.
+// ThreadBase::notify_one() wakes up the thread when there is some work to do
+
+void ThreadBase::notify_one() {
+
+  mutex.lock();
+  sleepCondition.notify_one();
+  mutex.unlock();
+}
+
+
+// ThreadBase::wait_for() set the thread to sleep until condition 'b' turns true
+
+void ThreadBase::wait_for(volatile const bool& b) {
+
+  mutex.lock();
+  while (!b) sleepCondition.wait(mutex);
+  mutex.unlock();
+}
+
+
+// Thread c'tor just inits data but does not launch any thread of execution that
+// instead will be started only upon c'tor returns.
 
 Thread::Thread() /* : splitPoints() */ { // Value-initialization bug in MSVC
 
-  searching = exit = false;
+  searching = false;
   maxPly = splitPointsSize = 0;
   activeSplitPoint = NULL;
   activePosition = NULL;
@@ -124,26 +144,6 @@ void MainThread::idle_loop() {
 }
 
 
-// Thread::notify_one() wakes up the thread when there is some search to do
-
-void Thread::notify_one() {
-
-  mutex.lock();
-  sleepCondition.notify_one();
-  mutex.unlock();
-}
-
-
-// Thread::wait_for() set the thread to sleep until condition 'b' turns true
-
-void Thread::wait_for(volatile const bool& b) {
-
-  mutex.lock();
-  while (!b) sleepCondition.wait(mutex);
-  mutex.unlock();
-}
-
-
 // Thread::cutoff_occurred() checks whether a beta cutoff has occurred in the
 // current active split point, or in some ancestor of the split point.
 
@@ -349,7 +349,7 @@ template void Thread::split< true>(Position&, Stack*, Value, Value, Value*, Move
 
 void ThreadPool::wait_for_think_finished() {
 
-  MainThread* t = main_thread();
+  MainThread* t = main();
   t->mutex.lock();
   while (t->thinking) sleepCondition.wait(t->mutex);
   t->mutex.unlock();
@@ -382,6 +382,6 @@ void ThreadPool::start_thinking(const Position& pos, const LimitsType& limits,
           || std::count(searchMoves.begin(), searchMoves.end(), *it))
           RootMoves.push_back(RootMove(*it));
 
-  main_thread()->thinking = true;
-  main_thread()->notify_one(); // Starts main thread
+  main()->thinking = true;
+  main()->notify_one(); // Starts main thread
 }