[PrematureStopping] Improve pause method using std::condition_variabl…

…e and locks.

Add COMPUTATION_CONTROLLERS macro to manage pause/cancel.
It will works also inside OpenMP environment.

Guarded from SWIG some methods which use SG_FORCED_INLINE.

src/shogun/machine/Machine.cpp

@@ -19,7 +19,7 @@ using namespace shogun;
 
 CMachine::CMachine()
     : CSGObject(), m_max_train_time(0), m_labels(NULL), m_solver_type(ST_AUTO),
-      m_cancel_computation(false), m_pause_computation(false)
+      m_cancel_computation(false)
 {
 	m_data_locked=false;
 	m_store_model_features=false;
@@ -61,8 +61,8 @@ bool CMachine::train(CFeatures* data)
 
 	auto sub = connect_to_signal_handler();
 	bool result = train_machine(data);
-    sub.unsubscribe();
-    reset_computation_variables();
+	sub.unsubscribe();
+	reset_computation_variables();
 
 	if (m_store_model_features)
 		store_model_features();

src/shogun/machine/Machine.h

@@ -23,6 +23,8 @@
 #include <shogun/labels/LatentLabels.h>
 #include <shogun/features/Features.h>
 
+#include <condition_variable>
+#include <mutex>
 #include <rxcpp/rx.hpp>
 
 namespace shogun
@@ -125,6 +127,11 @@ enum EProblemType
 	 */ \
 	virtual EProblemType get_machine_problem_type() const { return PT; }
 
+#define COMPUTATION_CONTROLLERS                                                \
+	if (cancel_computation())                                                  \
+		continue;                                                              \
+	pause_computation();
+
 /** @brief A generic learning machine interface.
  *
  * A machine takes as input CFeatures and CLabels (by default).
@@ -308,23 +315,36 @@ class CMachine : public CSGObject
 			return PT_BINARY;
 		}
 
+#ifndef SWIG
 		/** @return whether the algorithm needs to be stopped */
-		inline bool cancel_computation() const
+		SG_FORCED_INLINE bool cancel_computation() const
 		{
 			return m_cancel_computation.load();
 		}
+#endif
 
-		/** @return whether the algorithm needs to be paused */
-		inline bool pause_computation() const
+#ifndef SWIG
+		/** Pause the algorithm if the flag is set */
+		SG_FORCED_INLINE void pause_computation()
 		{
-			return m_pause_computation.load();
+			if (m_pause_computation_flag.load())
+			{
+				std::unique_lock<std::mutex> lck(m_mutex);
+				while (m_pause_computation_flag.load())
+					m_pause_computation.wait(lck);
+			}
 		}
+#endif
 
-		/** Unpause current computation (sets the flag) */
-		inline void unpause_computation()
+#ifndef SWIG
+		/** Resume current computation (sets the flag) */
+		SG_FORCED_INLINE void resume_computation()
 		{
-			m_pause_computation = false;
+			std::unique_lock<std::mutex> lck(m_mutex);
+			m_pause_computation_flag = false;
+			m_pause_computation.notify_all();
 		}
+#endif
 
 		virtual const char* get_name() const { return "Machine"; }
 
@@ -384,7 +404,7 @@ class CMachine : public CSGObject
 		void reset_computation_variables()
 		{
 			m_cancel_computation = false;
-			m_pause_computation = false;
+			m_pause_computation_flag = false;
 		}
 
 		/** The action which will be done when the user decides to
@@ -398,7 +418,9 @@ class CMachine : public CSGObject
 		* pause the CMachine execution */
 		virtual void on_pause()
 		{
-			m_pause_computation.store(true);
+			m_pause_computation_flag.store(true);
+			/* Here there should be the actual code*/
+			resume_computation();
 		}
 
 		/** The action which will be done when the user decides to
@@ -426,8 +448,14 @@ class CMachine : public CSGObject
 		/** Cancel computation */
 		std::atomic<bool> m_cancel_computation;
 
-		/** Pause computation */
-		std::atomic<bool> m_pause_computation;
+		/** Pause computation flag */
+		std::atomic<bool> m_pause_computation_flag;
+
+		/** Conditional variable to make threads wait */
+		std::condition_variable m_pause_computation;
+
+		/** Mutex used to pause threads */
+		std::mutex m_mutex;
 };
 }
 #endif // _MACHINE_H__