Made reported elapsed time more precise

benchmark.cpp

@@ -49,7 +49,7 @@ int main(int argc, char **argv)
 
       std::chrono::duration<double> elapsed = end_time - start_time;
 
-      printf("Elapsed time is: %.2f seconds\n", elapsed.count());
+      printf("Elapsed time is: %.6f seconds\n", elapsed.count());
 
       printf(" Sum result = %lld \n", t);