On Dec 1, 2009, at 6:05 PM, Roland Bock wrote:

Stonewall Ballard wrote: [...]

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In such a case, notify_one would wake less threads than required. But how can that happen with notify_one being called for each and every task? Take a look at this: <http://www.justsoftwaresolutions.co.uk/threading/implementing-a-thread-safe-queue-using-condition-variables.html> [...] I added the comment to the code in case someone came along later and decided that it was wasteful to notify_all().

Hmm. Have you read the section "UPDATE" on the page? To me that says that the requirement for the notify_all has already been taken care of in the presented code (by calling it each time a task is pushed).

Ah, I'd missed that. Thanks for pointing it out. It takes several readings to understand all this.

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My code is running in the idle loop of a dialog window, so I had to avoid blocking the producer for more than a moment. Since there could be many more available tasks than threads, a queue was the obvious choice.

Yes, a blocking dialog would be bad. I am using the threadpool for a merge process which can delegate the processing of chunks to its workers. At the time I wrote it, I thought that blocking would not be problem (and in the intended scenario it isn't), because I can rarely use all available threads due to the sheer size of the chunks. The merger blocks that anyway.

But after today, I think I will change my pool. Limiting the number of tasks is part of the merge logic, the pool should not do something like that.

May as well code a general-purpose pool so that it's debugged by the time you need it for another program. Thanks again for your help. - Stoney -- Stonewall Ballard stoney@sb.org http://stoney.sb.org/