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    <p>A few thoughts:</p> <ul> <li>Setting max concurrent operations so high is not going to have much effect. It's unlikely to be more than two if you have two cores</li> <li>It looks as though you're using the same <code>NSManagedObjectContext</code> for all your processes. This is Not Good</li> <li>Let's assume that your max concurrent operations <em>was</em> 100. The bottle-neck would be the main thread, where you're trying to update a label for every operation. Try to update the main thread for every <em>n</em> records instead of every one</li> <li>You shouldn't need to lock the context if you're using Core Data correctly... which means using a different context for each thread</li> <li>You don't seem to ever save the context?</li> <li>Batching operations is a good way to improve performance... but see previous point</li> <li>As you suggest, there's an overhead in creating a GCD operation. Creating a new one for each word is probably not optimal. You need to balance the overhead of creating a new processes with the benefits of parallelisation</li> </ul> <p>In short, threading is hard, even when you use something like GCD. </p>
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    1. COFirst point: 100 could be too much but 2 not enough to stress the CPU. I tried using 2 as maxConcurrencyOperation and the process start slow. Second point: I tried it as well. There is the problem to save the context every loop and it bring a lot of overhead. Third point: Seems really interesting. This will be the first try :) Fourth point: same as second point. Fifth point: I have a KVO on the NSOperationQueue. I save it when the Queue is empty. Seventh point: Really interesting. I'll try to group them. Thank you so much.
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      1. USGabriele
    2. CO"A consequence of this is that a context assumes the default owner is the thread or queue that allocated it—this is determined by the thread that calls its init method. You should not, therefore, initialize a context on one thread then pass it to a different thread. Instead, you should pass a reference to a persistent store coordinator and have the receiving thread/queue create a new context derived from that." https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObjectContext_Class/NSManagedObjectContext.html
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    3. COYou should be able to max out your machine with two concurrent processes. Any more and an increasing amount of time will be spent context switching rather than executing your own code. You're likely constrained by locking and waiting on the main thread.
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