In general, nothing can be said about the relative order of their execution.
Now, let’s consider your specific problem. If:
- both processes take a non-trivial amount of time to run, and
- you’re saying that one runs to completion before the other makes any progress, and
- there are unused CPU cycles, and
- this happens every time you run the application.
Most likely this indicates that there is some (perhaps unintended) synchronization going on between the two processes.