Merge pull request #9 from eddelbuettel/feature/optional-graph-file

make graph file writing optional

Author: iritkatriel

src/engine.h

@@ -168,7 +168,9 @@ namespace streamulus
 
         void StartEngine()
         {
+#if defined(WRITE_GRAPH)
             WriteGraph("TsGraph.vis");
+#endif
             ActivateSources();
             Work();            
         }