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 > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > >
