Re: NSRunLoop vs. NSThread sleep
On 29 Apr 2009, at 00:57, Eric Hermanson wrote: When implementing the while-loop in the main function of an NSThread, is it correct to assume it is more efficient on the operating system to run the current run-loop until a specified date rather than just use NSThread sleepUntilDate to obtain the delay? If you're talking about a secondary thread, NSThread's -sleepUntilDate is probably better. But you don't even need to use that; you could use sleep() or nanosleep() or even select(). However... I ask because I don't really need a formal run loop or special input source as I'm just checking a shared queue for data (and the delay is to allow the thread to gracefully exit). ...you shouldn't be polling your shared queue, *unless* you have some real-time requirement that necessitates that architecture, *or* you're certain that, for the entire lifetime of your thread, the chances are that the queue will always be full by the time the thread gets to check it. If you aren't sure you need to poll, you probably don't want to be polling. What you should be doing instead is either using a semaphore or an NSConditionLock to set things up such that your thread doesn't run at all unless there's work to do. So it's simpler to code just the NSThread sleep, however, I am guessing that will cause me context switching performance issues and I'd be better off using the NSRunLoop? If the NSRunLoop has nothing to do, I imagine it does the same thing anyway. Finally, is it acceptable to use the NSThread's cancelled/ isCancelled mechanism to check for the thread-exit hint, rather than set/check a global variable in the NSThread threadDictionary (as Apple's documentation shows)? That's what -cancel and -isCancelled are designed for. That said, if I were implementing a thread to managed a work queue (which is what you're doing), I'd be inclined to override the default implementations so that they added an item to the work queue... that way the thread could block on the work queue and would wake up if someone sent - cancel to it. But all of this is somewhat academic in a way, because Apple has handily provided NSOperationQueue for you which is probably what you should be using unless you have some backwards compatibility requirement or some other requirement that NSOperationQueue doesn't satisfy. Kind regards, Alastair. -- http://alastairs-place.net ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: NSRunLoop vs. NSThread sleep
On Wed, Apr 29, 2009 at 6:00 AM, Alastair Houghton alast...@alastairs-place.net wrote: But all of this is somewhat academic in a way, because Apple has handily provided NSOperationQueue for you which is probably what you should be using unless you have some backwards compatibility requirement or some other requirement that NSOperationQueue doesn't satisfy. NSOperationQueue is broken: http://www.mikeash.com/?page=pyblog/dont-use-nsoperationqueue.html I am not under NDA at the moment, so I'll point out that 10.5.7 is rumored to have fixes for NSOperationQueue. If that bears out to be true, then by all means run with NSOperationQueue. If not, you might want to hold off until Snow Leopard -- it wouldn't be the first time that Apple engineers (or anyone else, for that matter) have tackled a bug but missed some corner cases until the next major release. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: NSRunLoop vs. NSThread sleep
On 29 Apr 2009, at 11:44, Kyle Sluder wrote: On Wed, Apr 29, 2009 at 6:00 AM, Alastair Houghton alast...@alastairs-place.net wrote: But all of this is somewhat academic in a way, because Apple has handily provided NSOperationQueue for you which is probably what you should be using unless you have some backwards compatibility requirement or some other requirement that NSOperationQueue doesn't satisfy. NSOperationQueue is broken: http://www.mikeash.com/?page=pyblog/dont-use-nsoperationqueue.html Yes, it is, though I was under the impression that not everyone was seeing problems with it. However, given the simpler sample program Mike put in the comments, it does look pretty borked to me. Anyway, there's always http://www.rogueamoeba.com/utm/2008/12/01/raoperationqueue-an-open-source-replacement-for-nsoperationqueue/ (for instance). Kind regards, Alastair. -- http://alastairs-place.net ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: NSRunLoop vs. NSThread sleep
On Wed, Apr 29, 2009 at 6:53 AM, Alastair Houghton alast...@alastairs-place.net wrote: On 29 Apr 2009, at 11:44, Kyle Sluder wrote: On Wed, Apr 29, 2009 at 6:00 AM, Alastair Houghton alast...@alastairs-place.net wrote: But all of this is somewhat academic in a way, because Apple has handily provided NSOperationQueue for you which is probably what you should be using unless you have some backwards compatibility requirement or some other requirement that NSOperationQueue doesn't satisfy. NSOperationQueue is broken: http://www.mikeash.com/?page=pyblog/dont-use-nsoperationqueue.html Yes, it is, though I was under the impression that not everyone was seeing problems with it. However, given the simpler sample program Mike put in the comments, it does look pretty borked to me. It appears that the reason not everybody can reproduce the problem is because the bug is hardware-dependent. Thus this fact won't save you unless your code won't ever escape your machine (or 10.5.7 fixes it, or you only support 10.6 and that fixes it). Anyway, there's always http://www.rogueamoeba.com/utm/2008/12/01/raoperationqueue-an-open-source-replacement-for-nsoperationqueue/ (for instance). Note that although this is of course the best code ever (ahem) it is not equally capable compared to NSOperationQueue. (It mostly does less, but has some extra capabilities as well.) However for what the poster is after it's probably a good fit, since it's basically a fancy worker thread. Mike ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
NSRunLoop vs. NSThread sleep
Hello, When implementing the while-loop in the main function of an NSThread, is it correct to assume it is more efficient on the operating system to run the current run-loop until a specified date rather than just use NSThread sleepUntilDate to obtain the delay? I ask because I don't really need a formal run loop or special input source as I'm just checking a shared queue for data (and the delay is to allow the thread to gracefully exit). So it's simpler to code just the NSThread sleep, however, I am guessing that will cause me context switching performance issues and I'd be better off using the NSRunLoop? Finally, is it acceptable to use the NSThread's cancelled/isCancelled mechanism to check for the thread-exit hint, rather than set/check a global variable in the NSThread threadDictionary (as Apple's documentation shows)? Thank You, - Eric ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
