On 8/25/23 14:27, Joe@bloow.edu wrote:

> "A work unit is a set of consecutive elements of range to be processed
> by a worker thread between communication with any other thread. The
> number of elements processed per work unit is controlled by the
> workUnitSize parameter. "
>
> So the question is how to rebalance these work units?

Ok, your question brings me back from summer hibernation. :)

This is what I do:

- Sort the tasks in decreasing time order; the ones that will take the most time should go first.

- Use a work unit size of 1.

The longest running task will start first. You can't get better than that. When I print some progress reporting, I see that most of the time N-1 tasks have finished and we are waiting for that one longest running task.

Ali
"back to sleep"

On Wednesday, 23 August 2023 at 13:03:36 UTC, Joe wrote:
> to download files from the internet.

Are they particularly big files? You might consider using one of the other libs that does it all in one thread. (i ask about size cuz mine ive never tested doing big files at once, i usually use it for smaller things, but i think it can do it)

> The reason why this causes me problems is that the downloaded files, which are cashed to a temporary file, stick around and do not free up space(think of it just as using memory) and this can cause some problems some of the time.

this is why im a lil worried about my thing, like do they have to be temporary files or can it be memory that is recycled?

On Friday, 25 August 2023 at 21:31:37 UTC, Ali Çehreli wrote:
> On 8/25/23 14:27, Joe@bloow.edu wrote:
>
> > "A work unit is a set of consecutive elements of range to be
> processed
> > by a worker thread between communication with any other
> thread. The
> > number of elements processed per work unit is controlled by
> the
> > workUnitSize parameter. "
> >
> > So the question is how to rebalance these work units?
>
> Ok, your question brings me back from summer hibernation. :)
>
> This is what I do:
>
> - Sort the tasks in decreasing time order; the ones that will take the most time should go first.
>
> - Use a work unit size of 1.
>
> The longest running task will start first. You can't get better than that. When I print some progress reporting, I see that most of the time N-1 tasks have finished and we are waiting for that one longest running task.
>
> Ali
> "back to sleep"


I do not know the amount of time they will run. They are files that are being downloaded and I neither know the file size nor the download rate(in fact, the actual download happens externally).

While I could use work unit of size 1 then problem then is I would be downloading N files at once and that will cause other problems if N is large(and sometimes it is).

There should be a "work unit size" and a "max simultaneous workers". Then I could set the work unit size to 1 and say the max simultaneous workers to 8 to get 8 simultaneous downloads without stalling.

On Friday, 25 August 2023 at 21:43:26 UTC, Adam D Ruppe wrote:
> On Wednesday, 23 August 2023 at 13:03:36 UTC, Joe wrote:
>> to download files from the internet.
>
> Are they particularly big files? You might consider using one of the other libs that does it all in one thread. (i ask about size cuz mine ive never tested doing big files at once, i usually use it for smaller things, but i think it can do it)
>
>> The reason why this causes me problems is that the downloaded files, which are cashed to a temporary file, stick around and do not free up space(think of it just as using memory) and this can cause some problems some of the time.
>
> this is why im a lil worried about my thing, like do they have to be temporary files or can it be memory that is recycled?

The downloading is simply a wrapper that provides some caching to a ram drive and management of other things and doesn't have any clue how or what is being downloaded. It passes a link to something like youtube-dl or yt-dlp and has it do the downloaded.

Everything works great except for the bottle neck when things are not balancing out. It's not a huge deal since it does work and, for the most part, gets everything downloaded but sorta defeats the purpose of having multiple downloads(which is much faster since each download seems to be throttled).

Increasing the work unit size will make the problem worse while reducing it to 1 will flood the downloads(e.g., having 200 or even 2000 downloads at once).

Ultimately this seems like a design flaw in ThreadPool which should auto rebalance the threads and not treat the number of threads as identical to the worker unit size(well, length/workerunitsize).

e.g., suppose we have 1000 tasks and set worker unit size to 100. This gives 10 workers and 10 workers will be spawned(not sure if this is limited to total number of cpu threads or not)

What would be nice is to be able to set worker unit size to 1 and this gives 1000 workers but limit concurent workers to, say 10. So we would have at any time 10 workers each working on 1 element. When one gets finished it can be repurposed for any unfinished tasks.

The second case is preferable since there should be no issues with balancing but one still gets 10 workers. The stalling comes from the algorithm design and not anything innate in the problem or workload itself.