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Re: MacOS + OpenMP

 

Once we figure out what is involved and any risks, we can make a
decision at that point.  I'm working under the assumption that this only
applies to the raytracing.

Wayne

On 3/1/2018 8:41 AM, Bernhard Stegmaier wrote:
> Currently, I fully agree with you.
> 
> The only spot right now where it has real impact is the raytracing 3d viewer.
> And for me it is also only 3x faster with threading, so not that critical for some “offline” functionality.
> 
> But more and more OpenMP stuff might get added which maybe will make an impact in future.
> This has caused much problems with the zone filling already…
> 
> So, from my point of view at least a clear strategy should be defined.
> 
> 
> Bernhard
> 
>> On 1. Mar 2018, at 14:34, Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx> wrote:
>>
>> On 01/03/18 14:29, Jon Evans wrote:
>>> It is also used for zone filling and in my new eeschema connectivity
>>> code that I'm hoping to get merged soon after V5 release.
>>>
>>> I'm happy to help with research / testing of alternatives if we can't
>>> use OpenMP on Mac. 
>>>
>> I'd like to hear from a *single* Apple user who designs boards of
>> sufficient complexity for the multithreading to really have an impact on
>> performance. What's next, rewriting Kicad in Objective-C?
>>
>> - my 5 cents
>>
>> Tom
>>
>>
>>> Jon
>>>
>>> On Thu, Mar 1, 2018, 08:26 Wayne Stambaugh <stambaughw@xxxxxxxxx
>>> <mailto:stambaughw@xxxxxxxxx>> wrote:
>>>
>>>    Ughh!  Thank you Apple.  I'm not opposed to this idea if OpenMP isn't a
>>>    viable option on macos.  I would like to see our macos port be on par
>>>    with linux and windows ports.
>>>
>>>    Wayne
>>>
>>>    On 3/1/2018 8:20 AM, Bernhard Stegmaier wrote:
>>>> I did look around a bit.
>>>> Looks like OpenMP isn’t a friend of Xcode clang, because Apple has its
>>>> own Grand Central Dispatch (libdispatch) implementation/library doing
>>>> similar things (at first glance, didn’t look into details).
>>>> So, I guess OpenMP maybe won’t happen soon with stock toolchain or we
>>>> would have to use non-stock toolchain (probably with all problems that
>>>> come with that - I have seen bad things mixing compilers, etc.).
>>>>
>>>> Seems to be quite easy to convert OpenMP for loop parallelisation
>>>    to GCD:
>>>> <<<
>>>> //#pragma omp parallel for
>>>> //for( signed int i = 0; i < aPolySet.OutlineCount(); ++i )
>>>> dispatch_queue_t queue =
>>>> dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
>>>> dispatch_apply(aPolySet.OutlineCount(), queue, ^(size_t i)
>>>> {
>>>> ...
>>>> }
>>>> );
>>>>>>>
>>>>
>>>> I just naively replaced all of the OpenMP for loops like above and now
>>>> 3d-Viewer uses all cores.
>>>> On my i7-3770T rendering time decreased from about 100s to 30s.
>>>>
>>>> I also did it for the ratsnest loop but didn’t notice any difference
>>>> (maybe my test PCB was just to small).
>>>>
>>>> I could play around a bit to put that stuff into some nice syntax
>>>    maybe
>>>> similar to what Microsoft has with concurrency::parallel_for_each
>>>>   https://msdn.microsoft.com/en-us/library/dd492857.aspx
>>>> So, at least ugly #ifdef around each parallel for loop could be
>>>    hidden.
>>>>
>>>> Don’t get me wrong, I don’t want to add just another parallelisation
>>>> library/mechanism.
>>>> And… I guess it won’t be possible to transparently cover all the
>>>    OpenMP
>>>> pragma stuff maybe needed inside for loop body or maybe other stuff
>>>> needed for GCD (e.g. when writing to variables outside for body).
>>>>
>>>> Thoughts? Would this be an option?
>>>>
>>>> Oh, yes:
>>>> I did look into using STL std::async.
>>>> Doesn’t seem to be a good idea, because it usually doesn’t seem to use
>>>> anything like thread pools, etc. on various platforms.
>>>> You probably don’t want to create that much threads… :) 
>>>>
>>>>
>>>> Regards,
>>>> Bernhard
>>>>
>>>>> On 1. Mar 2018, at 08:40, Bernhard Stegmaier
>>>    <stegmaier@xxxxxxxxxxxxx <mailto:stegmaier@xxxxxxxxxxxxx>
>>>>> <mailto:stegmaier@xxxxxxxxxxxxx
>>>    <mailto:stegmaier@xxxxxxxxxxxxx>>> wrote:
>>>>>
>>>>> I had a quick look where OpenMP is used.
>>>>>
>>>>> I found it somewhere in the connectivity/ratsnest code.
>>>>> I don’t know of any complaints in that area and even on my old HW I
>>>>> had never a bad experience.
>>>>>
>>>>> And then, 3D-Viewer.
>>>>>
>>>>> So, in my opinion it is basically only about 3D-Viewer… I don’t know
>>>>> if user experience will be that bad without OpenMP.
>>>>> IMHO it’s only the Raytracing view, which isn’t intended to be used
>>>>> for normal viewing stuff anyway.
>>>>>
>>>>> If I find some time over the weekend I will also try… but I don’t
>>>>> think it will be worth it.
>>>>>
>>>>>
>>>>> Regards,
>>>>> Bernhard
>>>>>
>>>>>> On 1. Mar 2018, at 00:50, Jeff Young <jeff@xxxxxxxxx
>>>    <mailto:jeff@xxxxxxxxx>
>>>>>> <mailto:jeff@xxxxxxxxx <mailto:jeff@xxxxxxxxx>>> wrote:
>>>>>>
>>>>>> Or rip it out and use STL?
>>>>>>
>>>>>>> On 28 Feb 2018, at 23:38, Jon Evans <jon@xxxxxxxxxxxxx
>>>    <mailto:jon@xxxxxxxxxxxxx>
>>>>>>> <mailto:jon@xxxxxxxxxxxxx <mailto:jon@xxxxxxxxxxxxx>>> wrote:
>>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> Does anyone have a working build setup for getting OpenMP-enabled
>>>>>>> KiCad out of MacOS?
>>>>>>> If so, please share how -- I tried for a bit but couldn't get it
>>>>>>> going (I'm not super familiar with the MacOS toolchain yet).
>>>>>>>
>>>>>>> We should make sure that the 5.0 release is built with OpenMP,
>>>>>>> otherwise our Mac users are going to have a slower user experience.
>>>>>>>
>>>>>>> -Jon
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> 


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