[poppler] RFC: upstream optional threading support in pdftoppm for simple testing

Albert Astals Cid aacid at kde.org
Mon Apr 8 15:51:50 PDT 2013 

El Dilluns, 8 d'abril de 2013, a les 06:53:10, Thomas Freitag va escriure:
> Am 08.04.2013 00:42, schrieb Albert Astals Cid:
> > El Diumenge, 7 d'abril de 2013, a les 22:07:46, Thomas Freitag va 
escriure:
> >> Am 07.04.2013 21:12, schrieb Albert Astals Cid:
> >>> El Diumenge, 7 d'abril de 2013, a les 16:31:52, Adam Reichold va 
escriure:
> >>>> Hello,
> >>>> 
> >>>> Am 07.04.2013 16:13, schrieb Albert Astals Cid:
> >>>>> El Dissabte, 6 d'abril de 2013, a les 17:43:54, Adam Reichold va
> > 
> > escriure:
> >>>>>> Hello,
> >>>>>> 
> >>>>>> Am 06.04.2013 17:14, schrieb Albert Astals Cid:
> >>>>>>> El Divendres, 5 d'abril de 2013, a les 21:43:28, Adam Reichold va
> >>>>> 
> >>>>> escriure:
> >>>>>>>> Hello again,
> >>>>>>>> 
> >>>>>>>> I was a bit in a rush at the first try. Sorry for that, I tidied it
> >>>>>>>> up
> >>>>>>>> slightly.
> >>>>>>> 
> >>>>>>> Maybe we should rename from UTILS_USE_THREAD to UTILS_USE_PTHREAD ?
> >>>>>>> 
> >>>>>>> Or add a comment somewhere that we only support pthreads for now
> >>>>>>> somewhere?
> >>>>>> 
> >>>>>> I would be fine with both.
> >>>>>> 
> >>>>>> Actually, since this is mostly meant for testing, I would be fine
> >>>>>> with
> >>>>>> not making it accessible via autotools or CMake at all, i.e. just add
> >>>>>> the definition to 'config.h' manually when and if we need it.
> >>>>> 
> >>>>> Makes sense to me, code-wise what's the difference between this and
> >>>>> the
> >>>>> code Thomas posted in the threading bug? Do you think this is
> >>>>> simpler/easier to understand?
> >>>> 
> >>>> Yes, the difference is that I left out the Windows-specific part and
> >>>> tried to keep it as simple as possible. For example, I think
> >>>> synchronizing on the job queue is simpler than synchronizing on the
> >>>> thread state. But of course, my implementation is not very efficient in
> >>>> terms of performance, just sufficient for testing.
> >>> 
> >>> Thomas would you be OK if we merge this patchset or you'd prefer yours
> >>> (more complex?) to be in?
> >> 
> >> Oh, I never thought to get a question like this. To answer it, I need to
> >> to go a little bit more far afield: When I started to implement it,
> >> first of all I need a test case. Therefore I made that hack to pdftoppm
> >> to use multiple threads under Windows (still my favorite programming
> >> platform, I'm too old to change my habits), the pthread version I made
> >> much later to run it over the PDF suite and so that You can test it,
> >> too. But it was never made to publish it.
> >> I think that a multi
> >> threading version of pdftoppm is not really necessary for the community.
> > 
> > If we replace community by final user, agreed.
> > 
> >> BUT: because we now support multi threading, we need a test case in
> >> general. I haven't review Adam's patch in detail, but if You think it is
> >> sufficient as test case (and I don't think, that anyone need a Windows
> >> test case), I can live with it. If You otherwise mean that we need a
> >> more general support also on Windows, I'll spend one or two weekends to
> >> revise my solution.
> > 
> > Honestly *I* don't need Windows support, but that's not *my* project but a
> > community one and you seem to need it so we need it.
> > 
> > What I didn't originally like about your patch is that it was a bit too
> > much intrusive for my taste, and to be honest Adam's a bit too.
> 
> The advantage of a "pdftoppm" test case is that we can use it in the
> regression test without any manipulation and can compare the multi
> threading results with the "normal" results. And with the actual state
> we still have different results
> 1. with damaged PDF where the "normal" pdftoppm produces output for
> pages which can not be rendered by copying the last producable page.
> 2. with the type 3 fonts where the caching produces "random" result.
> 3. with non embedded fonts where the decision which external font should
> be used is sometimes different.
> But to solve this even I don't need a windows solution. I did need it
> only in the past to set breakpoints to have an easier look at variables,
> memory and call stack.
> 
> > So that got me thinking into the fact that we don't really need much of
> > the
> > pdftoppm code, we just need to create a SplashOutputDev and feed it into a
> > few threads.
> > 
> > So what do you think of "separate" non pdftoppm code in the test/ folder?
> > 
> > This way we can even have a thread_pthread_test.cpp and a
> > thread_windows_test.cpp, etc. without "polluting" the regular pdftoppm
> > code.
> What do You think about Adam's qt testcase? It has the advantage of not
> only test the rendering, even if it need some enhancements, because You
> still cannot modify the same annotation from different threads at the
> same time.

I do like it, and being Qt has the benefit of being multiplatform already, but 
it has the problem of not being pdftoppm and thus not a drop-in replacement.

Oh the decisions one has to take :D

Ok, so what does this like?

Take Adam's "qt test" and add it to qt/tests to have a "multiplatform 
stressing tool"

Take Adam's "non introsuive pthread additions to pdftoppm" to have a "drop in 
replacement for the test suite"

This way we get both sides happy?

Yes?

Albert

> 
> Cheers,
> Thomas
> 
> > Thoughts?
> > 
> > Cheers,
> > 
> >    Albert
> >> 
> >> So I band the ball back to You.
> >> Cheers,
> >> Thomas
> >> 
> >>> Cheers,
> >>> 
> >>>     Albert
> >>>> 
> >>>> Best regards, Adam.
> >>>> 
> >>>>> Cheers,
> >>>>> 
> >>>>>     Albert
> >>>>>> 
> >>>>>> Best regards, Adam.
> >>>>>> 
> >>>>>>> Besides that it looks ok-ish in a quick look.
> >>>>>>> 
> >>>>>>> Anyone has a comment?
> >>>>>>> 
> >>>>>>> Cheers,
> >>>>>>> 
> >>>>>>>     Albert
> >>>>>>>> 
> >>>>>>>> Best regards, Adam.
> >>>>>>>> 
> >>>>>>>> Am 05.04.2013 19:27, schrieb Adam Reichold:
> >>>>>>>>> Hello everyone,
> >>>>>>>>> 
> >>>>>>>>> To make it easier for us to test changes w.r.t. to threading, I
> >>>>>>>>> would
> >>>>>>>>> propose to commit a simple implementation of threading in
> >>>>>>>>> 'pdftoppm'
> >>>>>>>>> to
> >>>>>>>>> master.
> >>>>>>>>> 
> >>>>>>>>> The attached patch contains a very simple implementation that is
> >>>>>>>>> not
> >>>>>>>>> focused on maximal performance but should suffice to stress the
> >>>>>>>>> locking
> >>>>>>>>> inside Poppler's core. I opted to implement only the POSIX
> >>>>>>>>> approach
> >>>>>>>>> since I suppose POSIX systems are where most of us test and the
> >>>>>>>>> code
> >>>>>>>>> is
> >>>>>>>>> hopefully simple and short enough not become a maintenance burden.
> >>>>>>>>> 
> >>>>>>>>> What do you think?
> >>>>>>>>> 
> >>>>>>>>> Best regards, Adam.
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>>> _______________________________________________
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> >>>>>>> 
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