Update signal_handling.h

Edited comments.

src/common/signal_handling.h

@@ -3,25 +3,24 @@
 
 // SIGNAL HANDLING
 
-// The Marian signal handlers set global flags that thread can
+// The Marian signal handlers set global flags that threads can
 // consider when a signal is received. This can be used for a graceful
 // shutdown instead of a hard abandonment, e.g.  after receiving
 // SIGTERM during training.
 
-// When SIGTERM is received, the global (static member) flag sigterm_
-// (false by default) is set to true by signalHandler(). When sigterm_
-// is true, keepGoing() returns false, and the current state of
-// training models is saved prior to exiting.  This functionality is
-// helpful when training on clusters with time limits on compute
+// When SIGTERM is received, the global bit flag for SIGTERM
+// (false by default) is set to true by setSignalFlag. Threads involved in training
+// (batch generator, scheduler) periodicly check this flag and gracefully exit; 
+// the current state of training models is then saved prior to exiting the program.
+// This functionality is helpful when training on clusters with time limits on compute
 // slots, e.g., on s clusters managed by slurm. Slurm can be asked to
 // sending a (custom) warning signal to a process at a given point in
 // time prior to the hard "time's up".
 //
 // Correspondingly, fetchBatches in the batch generator checks the flag
 // frequently and quits after the overall process receives a SIGTERM.
 
-
 namespace marian {
 bool getSignalFlag(int sig); // return true if sig was received, false otherwise
-void setSignalFlag(int sig); // set custom handler (set flag) for sig
+void setSignalFlag(int sig); // custom handler (set flag) for sig
 }