Please consider adding a timestamp to each line of the stderr.txt file. The best location would be at the beginning of each line. The timestamps would help users and project administrators learn where slow and fast parts of each result that is returned are located, and could help the project developers develop better algorithms on how to split the search space into work units that are more consistent in how much time they take. The time stamp should be in UTC if possible so that you won't get confused by people who regularly change time zones like road warriors and globetrotters with laptops that run this project.

One other thing: if you do include timestamps, you should also timestamp the times the application is suspended, quit, or starts so that you would not get confused by those events.