kicad-developers team mailing list archive

[Bernhard Stegmaier <stegmaier@xxxxxxxxxxxxx>]

Hi all,

could please anybody test the following on a Windows/Linux OpenMP version?

I have a PCB with only components placed (via “Update from Schematic”), no routing done yet.
Make sure 3d-viewer OpenGL rendering is OK, close 3d-viewer.
Now, edit a footprint (“e”) and do a “Update Footprint from Library” for only this footprint (no changes in footprint needed).
Open 3d-viewer again.

Or:
Open PCB as above with only components and no routing yet.
Make sure that 3d-viewer in OpenGL mode is fine, close 3d-viewer.
Delete some of the components and reimport them vie “Update PCB from Schematic”.
Open 3d-viewer again.

In both cases my OpenMP builds (clang-5.0.1 with libomp-3.1) crash or hang (all cores at 100%, grey window, nothing happens) 3d-viewer .
It doesn’t hang/crash in my non-OpenMP builds.

If I save the PCB after the changes, close and reopen KiCad, then 3d-viewer of OpenMP build is also fine again.


Regards,
Bernhard

> On 3. Mar 2018, at 20:33, Bernhard Stegmaier <stegmaier@xxxxxxxxxxxxx> wrote:
> 
> Hi all,
> 
> So, I played around a bit to get OpenMP and GCD into something like a “parallel_for” wrapper which either uses OpenMP or GCD.
> Unfortunately, OpenMP seems to require that the “for” statement directly follows the “#pragma omg for …”.
> That currently killed all my attempts to define such a “parallel_for” (as function, #define, ?) so that the code will stay the same for both.
> One option would be to pull the “#pragma omp for …” into the wrapper, but I guess this is not really acceptable (since you can’t specify any specific schedule parameters any longer).
> 
> I will think about it some more just because of the challenge… but I am not very optimistic at the moment to get something nice.
> If anyone else has a nice idea, I’d be very interested to learn freaky new stuff… :)
> 
> On the other side, I looked at using a non-Xcode OpenMP capable clang.
> The only caveat seems to be not to mix standard C++ libraries (in the past libc++/libstdc++ haven’t been compatible in some aspects - didn’t try to find out if that is resolved).
> Default on macOS now is libc++, but it seems that at least MacPorts builds clang with libstdc++ per default (no idea why).
> The MacPorts build can easily be switched to libc++.
> That clang-mp builds KiCad without problems even if dependencies have been built with Xcode clang.
> Everything seems to work as expected, multithreading is there where it should be.
> 
> So, for now it seems to be the most easy solution to switch to a suitable non-Xcode clang for building packages - if we want to have OpenMP for macOS.
> 
> AFAIK our build machines use Homebrew.
> Seems as if Homebrew decides which standard library to use depending on macOS version (https://docs.brew.sh/C++-Standard-Libraries <https://docs.brew.sh/C++-Standard-Libraries>).
> So, if everything is recent enough it might not be a problem at all… like it obviously also has been for Seth below.
> 
> 
> Regards,
> Bernhard
> 
>> On 1. Mar 2018, at 17:47, Seth Hillbrand <seth.hillbrand@xxxxxxxxx <mailto:seth.hillbrand@xxxxxxxxx>> wrote:
>> 
>> Hi All-
>> 
>> I was playing with this last night (don't normally compile on the mac) and found that using homebrew's llvm 3.8.1 seems to compile fine with -fopenmp.  Running some OMP test code from https://gist.github.com/sethhillbrand/45dfb50e5a1865ad65bda1d6522778c5 <https://gist.github.com/sethhillbrand/45dfb50e5a1865ad65bda1d6522778c5> shows expected result of 4 threads.  I didn't get OpenMP errors when compiling KiCad although I didn't really notice a substantial difference in speed for the quick tests I was running.  Maybe with more involved operations.
>> 
>> I'm not sure if this will require us to distribute a different libstdc++ with KiCad.  Probably.  Does that seem feasible to the packing team?
>> 
>> -S
>> 
>> 2018-03-01 7:23 GMT-08:00 Bernhard Stegmaier <stegmaier@xxxxxxxxxxxxx <mailto:stegmaier@xxxxxxxxxxxxx>>:
>> Hmm?
>> You keep everything as is (especially creating threads), but just put the “#pragma …” before the for-loop.
>> So, there is one thread for the progress and one for the workers.
>> In the workers thread OpenMP (if there) takes care of adding additional threads for parallelising the loop?
>> 
>> Or, am I wrong with that?
>> 
>> > On 1. Mar 2018, at 16:11, Jeff Young <jeff@xxxxxxxxx <mailto:jeff@xxxxxxxxx>> wrote:
>> >
>> > But then the progress reporter won’t work (and you’ve got no way to cancel).
>> >
>> > Non-pooling parallel threads are sufficient for zone filling, aren’t they?
>> >
>> >
>> >> On 1 Mar 2018, at 15:00, Bernhard Stegmaier <stegmaier@xxxxxxxxxxxxx <mailto:stegmaier@xxxxxxxxxxxxx>> wrote:
>> >>
>> >> For now it would probably be fine to just restore the pragma for the for loop optimisation.
>> >> Mac users are used to work single-threaded, all others would get back multithreading here.
>> >>
>> >>> On 1. Mar 2018, at 15:58, Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx <mailto:tomasz.wlostowski@xxxxxxx>> wrote:
>> >>>
>> >>> On 01/03/18 15:43, Jeff Young wrote:
>> >>>> The purpose is it works on Mac.
>> >>>>
>> >>>> But it does appear I misread the std::max( omp_get_num_procs(), 2 ) part.
>> >>>>
>> >>>
>> >>> Thanks Jeff!
>> >>>
>> >>> Be aware that neither std::thread nor std::async have any concept of
>> >>> thread pooling - we need to look for a suitable library or write or own.
>> >>>
>> >>> Cheers,
>> >>> Tom
>> >>>
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>> 
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