Reformat threads code

Apart from some renaming the biggest change
is the retire of split_point_finished()
replaced by slavesMask flags. As a side
effect we now take also split point lock
when allocation available threads.

No functional change.

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

diff --git a/src/search.cpp b/src/search.cpp
index 2720edb373d8bba025b51cb431e160240d8f9fd8..f0bbf0fdecd013362a81f5037cb8d539e8c0495e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -573,20 +573,26 @@ namespace {
         thread.maxPly = ss->ply;
 
     // Step 1. Initialize node
         thread.maxPly = ss->ply;
 
     // Step 1. Initialize node

-    if (!SpNode)
-    {
-        ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
-        (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
-        (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
-    }
-    else
+    if (SpNode)

     {
     {

-        sp = ss->sp;

         tte = NULL;
         ttMove = excludedMove = MOVE_NONE;
         tte = NULL;
         ttMove = excludedMove = MOVE_NONE;

+        sp = ss->sp;

         threatMove = sp->threatMove;
         threatMove = sp->threatMove;

+        bestValue = sp->bestValue;
+        moveCount = sp->moveCount; // Lock must be held here
+
+        assert(bestValue > -VALUE_INFINITE && moveCount > 0);
+

         goto split_point_start;
     }
         goto split_point_start;
     }

+    else
+    {
+        ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
+        (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
+        (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+
+    }

 
     // Step 2. Check for aborted search and immediate draw
     // Enforce node limit here. FIXME: This only works with 1 search thread.
 
     // Step 2. Check for aborted search and immediate draw
     // Enforce node limit here. FIXME: This only works with 1 search thread.


@@ -820,14 +826,6 @@ split_point_start: // At split points actual search starts from here
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->type() & VALUE_TYPE_LOWER)
                            && tte->depth() >= depth - 3 * ONE_PLY;
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->type() & VALUE_TYPE_LOWER)
                            && tte->depth() >= depth - 3 * ONE_PLY;

-    if (SpNode)
-    {
-        lock_grab(sp->lock);
-        bestValue = sp->bestValue;
-        moveCount = sp->moveCount;
-
-        assert(bestValue > -VALUE_INFINITE && moveCount > 0);
-    }

 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs


@@ -1129,14 +1127,6 @@ split_point_start: // At split points actual search starts from here
         }
     }
 
         }
     }
 

-    if (SpNode)
-    {
-        // Here we have the lock still grabbed
-        sp->is_slave[pos.thread()] = false;
-        sp->nodes += pos.nodes_searched();
-        lock_release(sp->lock);
-    }
-

     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
 
     return bestValue;
     assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
 
     return bestValue;


@@ -1836,24 +1826,24 @@ void RootMove::insert_pv_in_tt(Position& pos) {
 
 
 /// Thread::idle_loop() is where the thread is parked when it has no work to do.
 
 
 /// Thread::idle_loop() is where the thread is parked when it has no work to do.

-/// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
-/// for which the thread is the master.
+/// The parameter 'master_sp', if non-NULL, is a pointer to an active SplitPoint
+/// object for which the thread is the master.

 
 

-void Thread::idle_loop(SplitPoint* sp) {
+void Thread::idle_loop(SplitPoint* sp_master) {

 
 

-  while (true)
+  // 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.
+  while (!sp_master || sp_master->slavesMask)

   {
       // If we are not searching, wait for a condition to be signaled
       // instead of wasting CPU time polling for work.
       while (   do_sleep
   {
       // If we are not searching, wait for a condition to be signaled
       // instead of wasting CPU time polling for work.
       while (   do_sleep

-             || do_terminate
-             || (Threads.use_sleeping_threads() && !is_searching))
+             || do_exit
+             || (!is_searching && Threads.use_sleeping_threads()))

       {
       {

-          assert((!sp && threadID) || Threads.use_sleeping_threads());
-
-          if (do_terminate)
+          if (do_exit)

           {
           {

-              assert(!sp);
+              assert(!sp_master);

               return;
           }
 
               return;
           }
 


@@ -1861,7 +1851,7 @@ void Thread::idle_loop(SplitPoint* sp) {
           lock_grab(sleepLock);
 
           // If we are master and all slaves have finished don't go to sleep
           lock_grab(sleepLock);
 
           // If we are master and all slaves have finished don't go to sleep

-          if (sp && Threads.split_point_finished(sp))
+          if (sp_master && !sp_master->slavesMask)

           {
               lock_release(sleepLock);
               break;
           {
               lock_release(sleepLock);
               break;


@@ -1880,46 +1870,42 @@ void Thread::idle_loop(SplitPoint* sp) {
       // If this thread has been assigned work, launch a search
       if (is_searching)
       {
       // If this thread has been assigned work, launch a search
       if (is_searching)
       {

-          assert(!do_terminate);
+          assert(!do_sleep && !do_exit);

 
           // Copy split point position and search stack and call search()
           Stack ss[MAX_PLY_PLUS_2];
 
           // Copy split point position and search stack and call search()
           Stack ss[MAX_PLY_PLUS_2];

-          SplitPoint* tsp = splitPoint;
-          Position pos(*tsp->pos, threadID);
-
-          memcpy(ss, tsp->ss - 1, 4 * sizeof(Stack));
-          (ss+1)->sp = tsp;
-
-          if (tsp->nodeType == Root)
-              search<SplitPointRoot>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
-          else if (tsp->nodeType == PV)
-              search<SplitPointPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
-          else if (tsp->nodeType == NonPV)
-              search<SplitPointNonPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+          SplitPoint* sp = splitPoint;
+          Position pos(*sp->pos, threadID);
+
+          memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
+          (ss+1)->sp = sp;
+
+          lock_grab(sp->lock);
+
+          if (sp->nodeType == Root)
+              search<SplitPointRoot>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+          else if (sp->nodeType == PV)
+              search<SplitPointPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+          else if (sp->nodeType == NonPV)
+              search<SplitPointNonPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);

           else
               assert(false);
 
           assert(is_searching);
 
           else
               assert(false);
 
           assert(is_searching);
 

+          // We return from search with lock held
+          sp->slavesMask &= ~(1ULL << threadID);
+          sp->nodes += pos.nodes_searched();
+          lock_release(sp->lock);
+

           is_searching = false;
 
           // Wake up master thread so to allow it to return from the idle loop in
           // case we are the last slave of the split point.
           if (   Threads.use_sleeping_threads()
           is_searching = false;
 
           // Wake up master thread so to allow it to return from the idle loop in
           // case we are the last slave of the split point.
           if (   Threads.use_sleeping_threads()

-              && threadID != tsp->master
-              && !Threads[tsp->master].is_searching)
-              Threads[tsp->master].wake_up();
-      }
-
-      // 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 && Threads.split_point_finished(sp))
-      {
-          // Because sp->is_slave[] is reset under lock protection,
-          // be sure sp->lock has been released before to return.
-          lock_grab(sp->lock);
-          lock_release(sp->lock);
-          return;
+              && threadID != sp->master
+              && !Threads[sp->master].is_searching)
+              Threads[sp->master].wake_up();

       }
   }
 }
       }
   }
 }

diff --git a/src/thread.cpp b/src/thread.cpp
index 81a718df8a0ff8e691cc7431736c2fd34378cb0d..3b7a10eeed31a2dc33415d2f5cbd6fe7037cc7c8 100644 (file)
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -97,12 +97,11 @@ bool Thread::is_available_to(int master) const {
 
   // Make a local copy to be sure doesn't become zero under our feet while
   // testing next condition and so leading to an out of bound access.
 
   // Make a local copy to be sure doesn't become zero under our feet while
   // testing next condition and so leading to an out of bound access.

-  int localActiveSplitPoints = activeSplitPoints;
+  int sp_count = activeSplitPoints;

 
   // No active split points means that the thread is available as a slave for any
   // other thread otherwise apply the "helpful master" concept if possible.
 
   // No active split points means that the thread is available as a slave for any
   // other thread otherwise apply the "helpful master" concept if possible.

-  if (   !localActiveSplitPoints
-      || splitPoints[localActiveSplitPoints - 1].is_slave[master])
+  if (!sp_count || (splitPoints[sp_count - 1].slavesMask & (1ULL << master)))

       return true;
 
   return false;
       return true;
 
   return false;


@@ -190,9 +189,11 @@ void ThreadsManager::init() {
 
 void ThreadsManager::exit() {
 
 
 void ThreadsManager::exit() {
 

+  assert(threads[0].is_searching == false);
+

   for (int i = 0; i <= MAX_THREADS; i++)
   {
   for (int i = 0; i <= MAX_THREADS; i++)
   {

-      threads[i].do_terminate = true; // Search must be already finished
+      threads[i].do_exit = true; // Search must be already finished

       threads[i].wake_up();
 
       thread_join(threads[i].handle); // Wait for thread termination
       threads[i].wake_up();
 
       thread_join(threads[i].handle); // Wait for thread termination


@@ -225,19 +226,6 @@ bool ThreadsManager::available_slave_exists(int master) const {
 }
 
 
 }
 
 

-// split_point_finished() checks if all the slave threads of a given split
-// point have finished searching.
-
-bool ThreadsManager::split_point_finished(SplitPoint* sp) const {
-
-  for (int i = 0; i < activeThreads; i++)
-      if (sp->is_slave[i])
-          return false;
-
-  return true;
-}
-
-

 // 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, or because we have no unused split
 // 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, or because we have no unused split


@@ -274,6 +262,7 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
   sp->parent = masterThread.splitPoint;
   sp->master = master;
   sp->is_betaCutoff = false;
   sp->parent = masterThread.splitPoint;
   sp->master = master;
   sp->is_betaCutoff = false;

+  sp->slavesMask = (1ULL << master);

   sp->depth = depth;
   sp->threatMove = threatMove;
   sp->alpha = alpha;
   sp->depth = depth;
   sp->threatMove = threatMove;
   sp->alpha = alpha;


@@ -286,9 +275,6 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
   sp->nodes = 0;
   sp->ss = ss;
 
   sp->nodes = 0;
   sp->ss = ss;
 

-  for (i = 0; i < activeThreads; i++)
-      sp->is_slave[i] = false;
-

   // If we are here it means we are not available
   assert(masterThread.is_searching);
 
   // If we are here it means we are not available
   assert(masterThread.is_searching);
 


@@ -298,21 +284,25 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
   // is_searching flag. This must be done under lock protection to avoid concurrent
   // allocation of the same slave by another master.
   lock_grab(threadsLock);
   // is_searching flag. This must be done under lock protection to avoid concurrent
   // allocation of the same slave by another master.
   lock_grab(threadsLock);

+  lock_grab(sp->lock); // To protect sp->slaves_mask

 
 

-  for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
+  for (i = 0; !Fake && i < activeThreads; i++)

       if (threads[i].is_available_to(master))
       {
       if (threads[i].is_available_to(master))
       {

-          workersCnt++;
-          sp->is_slave[i] = true;
+          sp->slavesMask |= (1ULL << i);

           threads[i].splitPoint = sp;
 
           threads[i].splitPoint = sp;
 

-          // This makes the slave to exit from idle_loop()
+          // Allocate the slave and make it exit from idle_loop()

           threads[i].is_searching = true;
 
           if (useSleepingThreads)
               threads[i].wake_up();
           threads[i].is_searching = true;
 
           if (useSleepingThreads)
               threads[i].wake_up();

+
+          if (++workersCnt >= maxThreadsPerSplitPoint)
+              break;

       }
 
       }
 

+  lock_release(sp->lock);

   lock_release(threadsLock);
 
   // We failed to allocate even one slave, return
   lock_release(threadsLock);
 
   // We failed to allocate even one slave, return


@@ -337,15 +327,17 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
   // finished. Note that changing state and decreasing activeSplitPoints is done
   // under lock protection to avoid a race with Thread::is_available_to().
   lock_grab(threadsLock);
   // finished. Note that changing state and decreasing activeSplitPoints is done
   // under lock protection to avoid a race with Thread::is_available_to().
   lock_grab(threadsLock);

+  lock_grab(sp->lock); // To protect sp->nodes
+

 
   masterThread.is_searching = true;
   masterThread.activeSplitPoints--;
 
   masterThread.is_searching = true;
   masterThread.activeSplitPoints--;

-
-  lock_release(threadsLock);
-

   masterThread.splitPoint = sp->parent;
   pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
 
   masterThread.splitPoint = sp->parent;
   pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
 

+  lock_release(sp->lock);
+  lock_release(threadsLock);
+

   return sp->bestValue;
 }
 
   return sp->bestValue;
 }
 


@@ -360,7 +352,7 @@ extern void check_time();
 
 void Thread::timer_loop() {
 
 
 void Thread::timer_loop() {
 

-  while (!do_terminate)
+  while (!do_exit)

   {
       lock_grab(sleepLock);
       timed_wait(sleepCond, sleepLock, maxPly ? maxPly : INT_MAX);
   {
       lock_grab(sleepLock);
       timed_wait(sleepCond, sleepLock, maxPly ? maxPly : INT_MAX);


@@ -396,7 +388,7 @@ void Thread::main_loop() {
       do_sleep = true; // Always return to sleep after a search
       is_searching = false;
 
       do_sleep = true; // Always return to sleep after a search
       is_searching = false;
 

-      while (do_sleep && !do_terminate)
+      while (do_sleep && !do_exit)

       {
           cond_signal(Threads.sleepCond); // Wake up UI thread if needed
           cond_wait(sleepCond, sleepLock);
       {
           cond_signal(Threads.sleepCond); // Wake up UI thread if needed
           cond_wait(sleepCond, sleepLock);


@@ -406,7 +398,7 @@ void Thread::main_loop() {
 
       lock_release(sleepLock);
 
 
       lock_release(sleepLock);
 

-      if (do_terminate)
+      if (do_exit)

           return;
 
       Search::think();
           return;
 
       Search::think();

diff --git a/src/thread.h b/src/thread.h
index 80363fa7f187aac9c65cec13314a879b2c4807a9..beb09e4d5df5700a212bb08db0b84e5a7c161a9a 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -50,12 +50,12 @@ struct SplitPoint {
 
   // Shared data
   Lock lock;
 
   // Shared data
   Lock lock;

+  volatile uint64_t slavesMask;

   volatile int64_t nodes;
   volatile Value alpha;
   volatile Value bestValue;
   volatile int moveCount;
   volatile bool is_betaCutoff;
   volatile int64_t nodes;
   volatile Value alpha;
   volatile Value bestValue;
   volatile int moveCount;
   volatile bool is_betaCutoff;

-  volatile bool is_slave[MAX_THREADS];

 };
 
 
 };
 
 


@@ -69,7 +69,7 @@ struct Thread {
   void wake_up();
   bool cutoff_occurred() const;
   bool is_available_to(int master) const;
   void wake_up();
   bool cutoff_occurred() const;
   bool is_available_to(int master) const;

-  void idle_loop(SplitPoint* sp);
+  void idle_loop(SplitPoint* sp_master);

   void main_loop();
   void timer_loop();
 
   void main_loop();
   void timer_loop();
 


@@ -85,7 +85,7 @@ struct Thread {
   volatile int activeSplitPoints;
   volatile bool is_searching;
   volatile bool do_sleep;
   volatile int activeSplitPoints;
   volatile bool is_searching;
   volatile bool do_sleep;

-  volatile bool do_terminate;
+  volatile bool do_exit;

 };
 
 
 };
 
 


@@ -110,7 +110,6 @@ public:
   void set_size(int cnt);
   void read_uci_options();
   bool available_slave_exists(int master) const;
   void set_size(int cnt);
   void read_uci_options();
   bool available_slave_exists(int master) const;

-  bool split_point_finished(SplitPoint* sp) const;

   void set_timer(int msec);
   void wait_for_stop_or_ponderhit();
   void stop_thinking();
   void set_timer(int msec);
   void wait_for_stop_or_ponderhit();
   void stop_thinking();