std.parallelism changes done

[Sönke Ludwig]

Am 24.03.2011 13:03, schrieb Michel Fortin:
> On 2011-03-24 03:00:01 -0400, Sönke Ludwig
> <ludwig at informatik.uni-luebeck.de> said:
>
>> Am 24.03.2011 05:32, schrieb dsimcha:
>>> In addition to improving the documentation, I added
>>> Task.executeInNewThread() to allow Task to be useful without a TaskPool.
>>> (Should this have a less verbose name?)
>>
>> The threading system I designed for the company I work for uses
>> priority per task to control which tasks can overtake others. A
>> special priority is out-of-bands (the name my be debatable), which
>> will guarantee that the task will run in its own thread so it can
>> safely wait for other tasks. However, those threads that process OOB
>> tasks are also cached in the thread pool and reused for new OOB tasks.
>> Only if the number of parallel OOB tasks goes over a specific number,
>> new threads will be created and destroyed. This can safe quite a bit
>> of time for those tasks.
>>
>> Both kinds of priority have been very useful and I would suggest to
>> put at least the executeInNewThread() method into ThreadPool to be
>> later able to make such an optimization.
>>
>> The task priority thing in general may only be necessary for complex
>> applications with user interaction, where you have to statisfy certain
>> interactivity needs. I wouldn't be too sad if this is not implemented
>> now, but it would be good to keep it in mind as a possible improvement
>> for later.
>
> Do you think having multiple task pools each with a different thread
> priority would do the trick? Simply put tasks in the task pool with the
> right priority... I had a similar use case in mind and this is what I
> proposed in the previous discussion.
>

Yes, that may be actually enough because although you would normally 
want to avoid the overhead of the additional threads running in 
parallel, in the scenarios I have in mind you always have unrelated 
things in different priority classes. An for these different tasks it 
should only be an exception to run in parallel (otherwise using 
priorities would be strange in the first place).

The only thing that is a bit of a pity is that now you have to manage 
multiple thread pools instead of simply using the one singleton instance 
in the whole application. And this could really cause some headaches if 
you have a lot of different types of workload that may all have 
different priorities but also may have the same - you would somehow have 
to share several thread pools across those types of workload.

(type of workload = copying files, computing a preview images, computing 
some physics calcs etc)