On Dec 5, 2012, at 01:09 , "Gerriet M. Denkmann" <gerr...@mdenkmann.de> wrote:
> When I press a button "Start" this gets done:
>
> self.start = [ NSDate date ];
> for( NSUInteger i = 0; i < self.nbrWork; i++ )
> {
> GmdOperationBasis *m2 = [ [ GmdOperationBasis alloc ] init ];
> [ self.operationQueue addOperation: m2 ];
> };
So operations are being created and queued while some already running, if I
understand correctly. That means your two possible sources of overhead (setup
and concurrency) might well be interacting badly with each other.
> No idea. But NSProcessInfo reports: processorCount = 8.
>
> About this Mac says: MacBook Pro; Retina, Mid 2012; Processor 2.3 GHz Intel
> Core i7; Memory 8 GB 1600 MHz DDR3.
That means you have 4 cores. In that case, it doesn't seem surprising that the
performance increase would be less dramatic after 3-4 threads, since your
operations are intensely compute-bound.
> This I cannot do.
> When I use NSOperationQueueDefaultMaxConcurrentOperationCount (i.e. letting
> NSOperationQueue decide what is appropriate) then my app will block (see
> thread: Operations Beachball).
Yeah, it's a difficult problem.
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