> On 1 Oct 2016, at 01:33, Quincey Morris
> wrote:
>
> On Sep 30, 2016, at 02:57 , Gerriet M. Denkmann wrote:
>
>> Any ideas where to look for a reason?
>
> The next step is probably to clarify the times between:
>
> a. Accumulated
On Sep 30, 2016, at 02:57 , Gerriet M. Denkmann wrote:
>
> dispatch_apply(8,…):
> My function is running 3090 msec and blocked 970 ms.
> And with dispatch_apply(20,000,…):
> My function is running 196 msec and blocked 27 ms.
In a way, this is good news, because a difference
> On 30 Sep 2016, at 10:57, Gerriet M. Denkmann wrote:
>
>
>
> But I just cannot see anything which forces my function to run 16 times
> longer in the first case.
>
> Any ideas where to look for a reason?
> On 29 Sep 2016, at 16:05, Roland King wrote:
>
>
>> On 29 Sep 2016, at 16:59, Gerriet M. Denkmann wrote:
>>
>>
>>> On 29 Sep 2016, at 15:34, Quincey Morris
>>> wrote:
>>>
>>
>> Well, I count this as (bigArea = 4
> On 29 Sep 2016, at 16:59, Gerriet M. Denkmann wrote:
>
>
>> On 29 Sep 2016, at 15:34, Quincey Morris
>> wrote:
>>
>> On Sep 29, 2016, at 01:05 , Gerriet M. Denkmann wrote:
>>>
>>> Well, nothing. Just let’s call
> On 29 Sep 2016, at 15:34, Quincey Morris
> wrote:
>
> On Sep 29, 2016, at 01:05 , Gerriet M. Denkmann wrote:
>>
>> Well, nothing. Just let’s call it nbrOfBlocksToBeUsedByDispatchApply, or
>> whatever. But ultimately any of these
> On 29 Sep 2016, at 10:05, Gerriet M. Denkmann wrote:
>
>
>> On 29 Sep 2016, at 14:38, Quincey Morris
>> wrote:
>>
>> On Sep 29, 2016, at 00:15 , Gerriet M. Denkmann wrote:
>>>
>>> dispatch_apply(
On Sep 29, 2016, at 01:05 , Gerriet M. Denkmann wrote:
>
> Well, nothing. Just let’s call it nbrOfBlocksToBeUsedByDispatchApply, or
> whatever. But ultimately any of these things has to run on a CPU, of which
> there are no more than 8.
Well, here’s my narrative. It may be
> On 29 Sep 2016, at 14:38, Quincey Morris
> wrote:
>
> On Sep 29, 2016, at 00:15 , Gerriet M. Denkmann wrote:
>>
>> dispatch_apply( nbrOfThreads, queue, ^void(size_t idx)
>>
>> As my computer has just 8 CPUs, I thought that using
On Sep 29, 2016, at 00:15 , Gerriet M. Denkmann wrote:
>
> dispatch_apply( nbrOfThreads, queue, ^void(size_t idx)
>
> As my computer has just 8 CPUs, I thought that using nbrOfThreads > 8 would
> be silly: adding overhead without gaining anything.
>
> Turns out this
My thoughts are general, not specific to Mac OS... The idea that the best
performance comes from threads = #CPUs is attractive, but will work only if
the threads do not sleep and do not interfere with each other. A classic
example is dividing up a complex calculation that runs without touching the
I have a big array (like a few GB) which is operated upon by some functions.
As these functions act purely local, an obvious idea is:
- (void)someFunction
{
nbrOfThreads = ...
sizeOfBigArray = ... a few GB
stride = sizeOfBigArray / nbrOfThreads
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