[Interest] how to run 21 threads concurrently

[Harri Pasanen]

Cancelling threads is a no-no in most threading systems I'm familiar 
with, so even reading such code somehow brushes me against feathers...

So out of habit I'd steer away from using cancel even if it were supported.

On 10/05/2012 12:34 AM, Alex Malyushytskyy wrote:
> Why do you need  Threads[th].cancel();?
> According to documentation not only "the QFuture returned by
> QtConcurrent::run() does not support canceling,...", but I do not see
> any reason you could want to do this.
>
> Alex
>
>
>
> On Thu, Oct 4, 2012 at 6:25 AM, André Somers <andre at familiesomers.nl> wrote:
>> Op 4-10-2012 15:21, Sujan Dasmahapatra schreef:
>>> I am not able to run my threads concurrently please help.
>>> How can I  run 21 threads concurrently and get the job done by 8 cpus
>>> what I have in my machine.
>>>
>>> I am doing like this
>>> [code]
>>>
>>> std::vector<QFuture<void> > Threads;
>>> QFuture<void> Th;
>>>
>>> for(int z=0; z<21; z++)
>>> {
>>> Th = QtConcurrent::run(this,&UnrstParser,z);
>>> Thraeds.push_back(Th);
>>> }
>>> for(int th=0; th<Threads.size(); th++)
>>> {
>>>   if(Threads[th].isRunning())
>>> Threads[th].waitForFinished();
>>> Threads[th].cancel();
>>> }
>>> Threads.clear();
>>> [/code]
>>>
>>> With this first few threads are probably running but not all the
>>> threads. As it's supposed to generate some files by each thread which
>>> is not being generated. Please help.
>>>
>>>
>> QtConcurrent will use as many threads as it deems useful, based on the
>> system you are running on. Unless you have a 21 core system, it is
>> probably not useful to run 21 threads your your task.
>> However, QThreadPool has methods to change how many threads are
>> considdered useful, so you should look into using that class.
>>
>> André
>>
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