>>> orbital ~/devtools/libphutil $ ./scripts/test/parallelism.php 10 2 1
[T = 0.0] Starting 10 tasks, which would require 61 seconds to run serially, and will take 1 each to post-process, at limit 4.
[T = 6.0] Completed a task.
[T = 8.0] Completed a task.
[T = 10.0] Completed a task.
[T = 11.0] Completed a task.
[T = 12.0] Completed a task.
[T = 13.0] Completed a task.
[T = 14.0] Completed a task.
[T = 17.0] Completed a task.
[T = 18.0] Completed a task.
[T = 20.0] Completed a task.
[T = 20.0] Done.