20364: Fixes issue when using shared objects / dynamically linked lib…

…raries where not explicitly setting the number of threads could yield low performance or unexpected behavior (#134)

src/Amalgam/ThreadPool.cpp

@@ -22,6 +22,10 @@ void ThreadPool::SetMaxNumActiveThreads(int32_t new_max_num_active_threads)
 {
 	std::unique_lock<std::mutex> lock(threadsMutex);
 
+	//if zero is specified, attempt to get hardware concurrency
+	if(new_max_num_active_threads == 0)
+		new_max_num_active_threads = std::thread::hardware_concurrency();
+
 	//don't need to change anything
 	if(new_max_num_active_threads == maxNumActiveThreads || new_max_num_active_threads < 1)
 		return;

src/Amalgam/ThreadPool.h

@@ -35,6 +35,8 @@ class ThreadPool
 	}
 
 	//changes the maximum number of active threads
+	//if max_num_active_threads is 0, it will attempt to ascertain and
+	//use the number of cores specified by hardware
 	void SetMaxNumActiveThreads(int32_t max_num_active_threads);
 
 	//returns the current maximum number of threads that are available