Single threaded executor is used for callbacks of two nodes

[sayali-purdue]

In file cv_pcl_node.cpp, single-threaded executor is used to process callbacks of two ROS nodes: cv_node and pcl_node. That means single thread is responsible for executing callbacks from two different callback groups (one default callback group per node). As discussed in ROS documentation, callbacks from different callback groups can execute in parallel. However due to single thread, the callbacks of the two nodes can not execute in parallel. Using a multi-threaded executor would be more efficient for this use case.

I would appreciate to hear your thoughts on this.