[Question] How to start tasks approximately in order

[Pr0methean]

I have a Vec of tasks that vary widely in duration. To maximize utilization of the whole thread pool, I want the tasks at lower indices in the Vec to start soonest, so that the last long-running task runs in parallel with some short-running tasks rather than becoming a bottleneck at the end. How do I ensure this? Right now I'm using

        let planned_tasks: Vec<CloneableLazyTask<()>>
            = large_tasks.into_iter().chain(small_tasks.into_iter()).collect();
        planned_tasks.into_par_iter().for_each(move |task| {
            let name = task.name.to_owned();
            task.into_result()
                .unwrap_or_else(|err| panic!("Error running task {}: {:?}", name, err));
        });

However, the ordering within large_tasks also matters.

[cuviper]

Maybe scope_fifo and its associated spawn_fifo would suit you better? Then you would not need planned_tasks at all, just create a scope and then spawn the tasks directly from their original sources.

[Pr0methean]

Thanks; I'll test that once tonight's nightly Rust build comes out (I'm blocked by rust-lang/rust#112831).