Stress is one stress-testing run. The generator is invoked repeatedly with random arguments; every input it produces goes through the validator, then to the reference solution for the answer and to every other selected solution, whose output the checker compares against that answer. The run ends when its budget is spent or, by default, at the first counterexample. A stress is kept for a limited time only — what is worth keeping is added to the problem as a test, using the arguments of the failing run.