Allow execution of tasks on the global thread pool.

src/thread.cpp

@@ -80,6 +80,13 @@ void Thread::start_searching() {
   cv.notify_one(); // Wake up the thread in idle_loop()
 }
 
+void Thread::execute_task(std::function<void(Thread&)> t)
+{
+  std::lock_guard<std::mutex> lk(mutex);
+  task = std::move(t);
+  cv.notify_one(); // Wake up the thread in idle_loop()
+}
+
 
 /// Thread::wait_for_search_finished() blocks on the condition variable
 /// until the thread has finished searching.
@@ -109,14 +116,22 @@ void Thread::idle_loop() {
       std::unique_lock<std::mutex> lk(mutex);
       searching = false;
       cv.notify_one(); // Wake up anyone waiting for search finished
-      cv.wait(lk, [&]{ return searching; });
+      cv.wait(lk, [&]{ return searching || task; });
 
       if (exit)
           return;
 
       lk.unlock();
 
-      search();
+      if (task)
+      {
+        task(*this);
+        task = nullptr;
+      }
+      else
+      {
+        search();
+      }
   }
 }
 
@@ -162,6 +177,14 @@ void ThreadPool::clear() {
 }
 
 
+void ThreadPool::execute_parallel(std::function<void(Thread&)> task)
+{
+  for(Thread* th : *this)
+  {
+    th->execute_task(task);
+  }
+}
+
 /// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
 /// returns immediately. Main thread will wake up other threads and start the search.
 

src/thread.h

@@ -24,6 +24,7 @@
 #include <mutex>
 #include <thread>
 #include <vector>
+#include <functional>
 
 #include "material.h"
 #include "movepick.h"
@@ -50,10 +51,12 @@ public:
   explicit Thread(size_t);
   virtual ~Thread();
   virtual void search();
+  virtual void execute_task(std::function<void(Thread&)> t);
   void clear();
   void idle_loop();
   void start_searching();
   void wait_for_search_finished();
+  size_t thread_idx() const { return idx; }
 
   Pawns::Table pawnsTable;
   Material::Table materialTable;
@@ -78,6 +81,7 @@ public:
   bool UseRule50;
   Depth ProbeDepth;
 
+  std::function<void(Thread&)> task;
 };
 
 
@@ -105,6 +109,8 @@ struct MainThread : public Thread {
 
 struct ThreadPool : public std::vector<Thread*> {
 
+  void execute_parallel(std::function<void(Thread&)> task);
+
   void start_thinking(Position&, StateListPtr&, const Search::LimitsType&, bool = false);
   void clear();
   void set(size_t);

src/uci.cpp

@@ -345,6 +345,12 @@ void UCI::loop(int argc, char* argv[]) {
       // Command to call qsearch(),search() directly for testing
       else if (token == "qsearch") qsearch_cmd(pos);
       else if (token == "search") search_cmd(pos, is);
+      else if (token == "tasktest")
+      {
+        Threads.execute_parallel([](auto& th) {
+          std::cout << th.thread_idx() << '\n';
+        });
+      }
 
       // test command
       else if (token == "test") test_cmd(pos, is);