Function run_pbt 

pub fn run_pbt(
    problem: &ScheduleProblem,
    pbt: &Pbt,
    budget: u64,
    seed: u64,
) -> Result<PbtReport>

Runs single-worker PBT over problem for budget trials and records the population, the winner and the schedule it discovered.

The population is the set of concurrent trials the loop drives (one worker, so the trajectory is reproducible). Each trial trains one segment from its parent’s carried checkpoint and records its own, so PBT’s exploit copies real checkpoint references through the real loop.

Errors

Anything the study loop, storage or the objective reports. A fork is not an error — the loop records it and carries on.