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POboost::thread_group - is it ok to call create_thread after join_all?
 

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  1. POboost::thread_group - is it ok to call create_thread after join_all?
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    <p>I have the following situation:</p> <p>I create a boost::thread_group instance, then create threads for parallel-processing on some data, then join_all on the threads.</p> <p>Initially I created the threads for every X elements of data, like so:</p> <pre><code>// begin = someVector.begin(); // end = someVector.end(); // batchDispatcher = boost::function&lt;void(It, It)&gt;(...); boost::thread_group processors; // create dispatching thread every ASYNCH_PROCESSING_THRESHOLD notifications while(end - begin &gt; ASYNCH_PROCESSING_THRESHOLD) { NotifItr split = begin + ASYNCH_PROCESSING_THRESHOLD; processors.create_thread(boost::bind(batchDispatcher, begin, split)); begin = split; } // create dispatching thread for the remainder if(begin &lt; end) { processors.create_thread(boost::bind(batchDispatcher, begin, end)); } // wait for parallel processing to finish processors.join_all(); </code></pre> <p>but I have a problem with this: When I have lots of data, this code is generating lots of threads (> 40 threads) which keeps the processor busy with thread-switching contexts.</p> <p>My question is this: Is it possible to call create_thread on the thread_group <em>after</em> the call to join_all.</p> <p>That is, can I change my code to this?</p> <pre><code>boost::thread_group processors; size_t processorThreads = 0; // NEW CODE // create dispatching thread every ASYNCH_PROCESSING_THRESHOLD notifications while(end - begin &gt; ASYNCH_PROCESSING_THRESHOLD) { NotifItr split = begin + ASYNCH_PROCESSING_THRESHOLD; processors.create_thread(boost::bind(batchDispatcher, begin, split)); begin = split; if(++processorThreads &gt;= MAX_ASYNCH_PROCESSORS) // NEW CODE { // NEW CODE processors.join_all(); // NEW CODE processorThreads = 0; // NEW CODE } // NEW CODE } // ... </code></pre> <p>Whoever has experience with this, thanks for any insight.</p>
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