I'd prefer if we keep discussions on the dev-list instead of slack - feel
free to open another thread.

-Marco

Pedro Larroy <pedro.larroy.li...@gmail.com> schrieb am Fr., 12. Apr. 2019,
02:24:

> I will respond in slack, so we don't derail the original thread's
> topic with my points.
>
> Looking forward to your proposal.
>
> On Thu, Apr 11, 2019 at 1:00 PM Junru Shao <junrushao1...@gmail.com>
> wrote:
> >
> > I don't have idea about the following issues:
> >
> > 1) Reducing the abuse of inlined code moving more logic to implementation
> > files and improve scoping which will also speed up compilation
> > 2) Reduce runtime of some unit tests
> > 3) Improve MXNet startup time
> >
> > Will be super interested to hear about your ideas :-)
> >
> >
> > On Thu, Apr 11, 2019 at 12:52 PM Junru Shao <junrushao1...@gmail.com>
> wrote:
> >
> > > We have a systematic solution to go without ABI headache. I am
> struggling
> > > with some errants, and will share our proposal here as soon as I could.
> > > This will be very interesting topic to discuss. Let's work hard
> together
> > > and make it perfect :-)
> > >
> > > On Thu, Apr 11, 2019 at 12:43 PM Pedro Larroy <
> > > pedro.larroy.li...@gmail.com> wrote:
> > >
> > >> Thanks Marco for raising this issue. I think we can certainly do some
> > >> improvements in modularization and build. At the same time Tianqi's
> > >> point of view is important to consider and on point. I see a high risk
> > >> of overengineering in such endeavor.
> > >>
> > >> I also see increased complexity, difficulty debugging, C++ ABI
> > >> headaches, API compatibility, crashes inside a binary module, etc.
> > >> which I don't want to deal with as a developer or even as an MXNet
> > >> user. Does somebody have answers to these problems?
> > >>
> > >> If somebody thinks they have a good solution, by all means propose a
> > >> design in the wiki, I think we are all open. Personally I see several
> > >> other lower hanging fruits which need our attention:
> > >>  * Simplifying our build logic,
> > >>  * Cuda selection in CMake,
> > >>  * Reducing the abuse of inlined code moving more logic to
> > >> implementation files and improve scoping which will also speed up
> > >> compilation, (some units take more than 5 minutes to build and lots of
> > >> RAM in a top of the line CPU core)
> > >>  * Reduce runtime of some unit tests
> > >> And other  improvements in our codebase that would bring immediate
> > >> benefits without the risks of overengineering of a plugin system. I
> > >> also question our bandwidth for such an endeavor.
> > >>  * Improve MXNet startup time.
> > >>  * Thread safety
> > >>
> > >> I would say, let's apply the KISS principle, let's make the project
> > >> fast to build, easy to work on, well documented and easy to contribute
> > >> to before building the next Netscape browser. Otherwise we could save
> > >> ourselves this exercise and switch to Rust directly.
> > >>
> > >> Pedro.
> > >>
> > >>
> > >>
> > >> On Mon, Apr 8, 2019 at 9:42 AM Tianqi Chen <tqc...@cs.washington.edu>
> > >> wrote:
> > >> >
> > >> > Just to clarify. I am not questioning the usefulness of the
> separation.
> > >> > Just want to highlight the technical challenges here based on our
> past
> > >> > experiences.
> > >> >
> > >> > Crossing DLL boundaries in C++ can create quite a lot of problems,
> > >> > especially some of the dependencies used a different version of the
> > >> > compiler, follows static packaging or simply because of the dynamic
> > >> linking
> > >> > difference in windows. These problems could make this direction move
> > >> less
> > >> > appealing compared to focusing effort on other things.
> > >> >
> > >> > Technically, as a first step, it is possible to make dependencies
> change
> > >> > not change the global header files and via registration so that
> changing
> > >> > certain component won't trigger a global recompile in CMake. This is
> > >> also a
> > >> > required step toward some modularity.
> > >> >
> > >> > For plugins, solutions that use C ABI can be used for certain plugin
> > >> > modules.
> > >> >
> > >> > Some of the discussion has been tied to what the interface should
> look
> > >> > like. I think we should use different threads for these and puts in
> more
> > >> > thoughts.
> > >> >
> > >> > Tianqi
> > >> >
> > >> >
> > >> >
> > >> > On Sun, Apr 7, 2019 at 4:39 PM kellen sunderland <
> > >> > kellen.sunderl...@gmail.com> wrote:
> > >> >
> > >> > > I think we can make some incremental progress.  My thoughts were
> > >> along the
> > >> > > lines of plugins (thinking about what happens with the VLC
> project).
> > >> At
> > >> > > process launch time we could gather some information about our
> > >> execution
> > >> > > environment (either through configuration, or by convention
> looking
> > >> at our
> > >> > > folder structure and libraries available).  We could then later
> load
> > >> the
> > >> > > components we need after understanding if we're using a CUDA
> backend
> > >> and
> > >> > > what operators or subgraph components we would need.  Advantages
> > >> would be
> > >> > > that we would move a lot of the current conditional compile logic
> to
> > >> > > runtime, and automate a lot of it.  It would also make packaging
> > >> binaries
> > >> > > for targeted environments a little easier.  As an example we could
> > >> compile
> > >> > > once, then remove CUDA focused libraries for systems that are
> going
> > >> to run
> > >> > > on CPUs.
> > >> > >
> > >> > > On Sun, Apr 7, 2019 at 2:45 PM Tianqi Chen <
> tqc...@cs.washington.edu>
> > >> > > wrote:
> > >> > >
> > >> > > > While I personally like the idea. This can be something that is
> > >> fairly
> > >> > > > technical challenging and I would caution against this idea vs
> > >> pushing
> > >> > > for
> > >> > > > good features and just allow runtime configuration.
> > >> > > >
> > >> > > > The main problem here is due to the C++ ABI. There is no
> standard
> > >> c++ ABI
> > >> > > > across compilers, which means resorting to runtime DLL and
> dynamic
> > >> > > loading
> > >> > > > brings all sorts of technical problems, especially when multiple
> > >> modules
> > >> > > > depend on the same third dependency(CUDA runtime).
> > >> > > > There is no good to go solution can be made here, especially
> given
> > >> the
> > >> > > > explosion of the backend variants and dependencies in C++.
> > >> > > > A partial solution could be achieved, through the sole use of C
> ABI.
> > >> > > > Combing this with code generation can result in some
> > >> simplifications and
> > >> > > > enable some runtime loadable module. TVM does this, and perhaps
> > >> MXNet
> > >> > > could
> > >> > > > reuse some of that component for operator libraries. Similarly,
> > >> having a
> > >> > > > customizable operator library that is loadable via C ABI might
> be
> > >> > > possible.
> > >> > > >
> > >> > > > So to summarize, while I really like the idea of dynamically
> > >> loadable
> > >> > > > modules. My past experience suggests that this will bring a lot
> of
> > >> > > > additional engineering burden and technical debts without
> > >> significant
> > >> > > > benefit. I would suggest starting by supporting something simple
> > >> like a
> > >> > > > plugin module, before moving toward the general direction.
> > >> > > >
> > >> > > > Tianqi
> > >> > > >
> > >> > > > On Sun, Apr 7, 2019 at 1:31 PM kellen sunderland <
> > >> > > > kellen.sunderl...@gmail.com> wrote:
> > >> > > >
> > >> > > > > Strongly support the idea of runtime loadable components in
> MXNet.
> > >> > > > There's
> > >> > > > > no reason (other than perhaps engineering effort) we can't
> have a
> > >> > > single
> > >> > > > > compilation of MXNet that finds dependencies and chooses
> execution
> > >> > > paths
> > >> > > > > intelligently (or based on configuration) at runtime.
> > >> > > > >
> > >> > > > > On Thu, Apr 4, 2019 at 12:29 PM Marco de Abreu <
> > >> marcoab...@apache.org>
> > >> > > > > wrote:
> > >> > > > >
> > >> > > > > > Hello,
> > >> > > > > >
> > >> > > > > > I'd like to start a discussion about something that I've
> noticed
> > >> > > being
> > >> > > > > > troublesome to maintain in the current version: Backend
> choices
> > >> being
> > >> > > > > made
> > >> > > > > > at compile time.
> > >> > > > > >
> > >> > > > > > Right now, the different backends and accelerators (CPU,
> cuda,
> > >> mkl,
> > >> > > AWS
> > >> > > > > > elastic inference, (future) AMD, openblas,TVM, etc) are all
> > >> scattered
> > >> > > > > > across the different layers of MXNet. On one hand, we have
> > >> compile
> > >> > > time
> > >> > > > > > flags that decide which backends are being compiled into the
> > >> binary,
> > >> > > > > while
> > >> > > > > > at the same time choices can be made in the frontend during
> > >> runtime.
> > >> > > > > >
> > >> > > > > > At the moment, we have a lot of conditional build logic that
> > >> picks
> > >> > > > > > different parts. With the addition of MKLML and later
> MKLDNN the
> > >> > > clear
> > >> > > > > > separation of CPU and GPU got kind of broken up. While we
> have
> > >> some
> > >> > > > > places
> > >> > > > > > where each code lives, in the end we resort to some files
> > >> containing
> > >> > > a
> > >> > > > > lot
> > >> > > > > > of conditional logic for the different backends (sorry I
> can't
> > >> > > provide
> > >> > > > > > links right now since I'm on mobile). To me this seems like
> a
> > >> residue
> > >> > > > of
> > >> > > > > > the fast development style from the early days (more
> processor
> > >> > > > statement
> > >> > > > > > and less object orientation) while also having organic
> growth
> > >> with
> > >> > > new
> > >> > > > > > accelerators. When I see how much AMD had to hack to fit in
> > >> their
> > >> > > > > > implementation, it seemed like we have to make this part
> more
> > >> > > developer
> > >> > > > > > friendly.
> > >> > > > > >
> > >> > > > > > At the moment, every new flavour of MXNet has to be entirely
> > >> > > > recompiled.
> > >> > > > > > This makes it hard for users to figure out which options to
> use,
> > >> > > while
> > >> > > > it
> > >> > > > > > makes it harder for us to test since the overhead to test
> every
> > >> > > single
> > >> > > > > > combination of compile parameters would be overwhelming.
> > >> > > > > >
> > >> > > > > > I'd propose to have a clear class hierarchy based structure
> for
> > >> > > > > > accelerators, operators and memory management. This
> structure
> > >> can
> > >> > > then
> > >> > > > be
> > >> > > > > > implemented by the different backends. To reduce the compile
> > >> burden,
> > >> > > we
> > >> > > > > > would introduce dynamic loading and split the different
> > >> backends into
> > >> > > > > > modules. These could then be developed, maintained and
> compiled
> > >> on
> > >> > > > their
> > >> > > > > > own and then placed in a "module" folder to be loaded at
> > >> runtime.
> > >> > > > Adding
> > >> > > > > a
> > >> > > > > > new accelerator would be a matter of placing the precompiled
> > >> binary
> > >> > > > into
> > >> > > > > > the folder. The detailed configuration of that Backend would
> > >> then be
> > >> > > > done
> > >> > > > > > on runtime - the user shouldn't worry at the point of
> > >> downloading
> > >> > > mxnet
> > >> > > > > > whether they want mkl, MKLDNN, mkl, openblas, atlas, TVM,
> cuda
> > >> or
> > >> > > what
> > >> > > > > ever
> > >> > > > > > else there is. I have an idea how we could help the user
> > >> choosing,
> > >> > > but
> > >> > > > > > that's outside the scope of this proposal.
> > >> > > > > >
> > >> > > > > > This would allow us to have a "core" MXNet that takes care
> of
> > >> the
> > >> > > > engine,
> > >> > > > > > scheduling, communication and all the other crucial parts.
> On
> > >> the
> > >> > > other
> > >> > > > > > hand we could make MXNet less of a monolith and have clear
> > >> > > interfaces.
> > >> > > > > This
> > >> > > > > > would also act as a forcing function because the different
> parts
> > >> > > > wouldn't
> > >> > > > > > be intermingled but have to follow the common interface.
> > >> > > > > >
> > >> > > > > > Of course this comes with the question what these interfaces
> > >> would
> > >> > > look
> > >> > > > > > like. For operators, I'd like to propose getting inspiring
> (or
> > >> fully
> > >> > > > > > adapting) ONNX. For memory management and other Backend
> specific
> > >> > > things
> > >> > > > > we
> > >> > > > > > could look at the current implementations and find a common
> > >> ground.
> > >> > > > > >
> > >> > > > > > Back when I had a community driven project, we heavily used
> this
> > >> > > > > modularity
> > >> > > > > > and it brought great benefits - besides the fact that our
> core
> > >> was
> > >> > > > closed
> > >> > > > > > source. It allowed community developers to act entirely
> > >> independent
> > >> > > > from
> > >> > > > > > other parts and even allowed them to add their own logic
> without
> > >> > > having
> > >> > > > > to
> > >> > > > > > touch the core. Thinking about companies that implement
> their
> > >> own
> > >> > > > > backends
> > >> > > > > > or have special tweaked operators without wanting to
> disclose
> > >> them,
> > >> > > > this
> > >> > > > > > structure would avoid them having to fork the project and
> then
> > >> spend
> > >> > > a
> > >> > > > > lot
> > >> > > > > > of effort porting the changes to the latest source release
> > >> versions.
> > >> > > > > > Instead, they would maintain their module and we as MXNet
> > >> community
> > >> > > > would
> > >> > > > > > only have to maintain these interfaces.
> > >> > > > > >
> > >> > > > > > Right now this is a lot of prosa and basically a brain dump
> of
> > >> my
> > >> > > > > thoughts.
> > >> > > > > > I'd be happy to follow up with details, but first I'd be
> > >> curious what
> > >> > > > the
> > >> > > > > > community thinks about this design.
> > >> > > > > >
> > >> > > > > > Best regards,
> > >> > > > > > Marco
> > >> > > > > >
> > >> > > > >
> > >> > > >
> > >> > >
> > >>
> > >
>

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