Naveen, software designing is all about tradeoff, every feature we introduce causes more compiling time, more efforts to maintain, etc.
The main difference is. Option #1: Java users do NDArray.BatchNorm(data, gamma, beta, null, null, null, null, null, null, null, null, null, null, null); (and because every operator has an argument "out", users need to add an extra "null" to the function call almost every time.) Option #2, Java users do JavaNDArray.BatchNorm(data).setGamma(gamma).setBeta(beta).invoke(); I don't think any of the reasons you listed is so important as the benefit above we got from option #2. On Sat, Sep 29, 2018 at 8:24 AM Naveen Swamy <mnnav...@gmail.com> wrote: > > Java APIs are not like Clojure - The current proposal is only to build a > few thin wrappers for Inference. > > To better represent the two cases and this discussion in particular, here > is an example API > > 1) def Activation (data : org.apache.mxnet.NDArray, act_type : String, out > : Option[NDArray] = None) : org.apache.mxnet.NDArrayFuncReturn > or > 2) def Activation (data : org.apache.mxnet.NDArray, act_type : String, out > : NDArray) : org.apache.mxnet.NDArrayFuncReturn > > The discussion is should we add(generate) 200+ APIs to make it Java > compatible, ie., remove the Option class and the None default value which > Java does not understand from Option 1) > > my suggestion was to remove the Option class and create a implicit for > backward compatibility and use null instead of None, Andrew and I disagreed > on this, so I suggested to raise a discussion on dev@ to get more opinions > and one of us will disagree and commit. Thanks for raising it :) > > | * def Activation (data : org.apache.mxnet.NDArray, act_type : String, out > : NDArray = null) : org.apache.mxnet.NDArrayFuncReturn | > -- > > 1) It is not true that Scala users will lose *default/optional* arguments - > if we followed the above, they will use null or None, though I do not like > using nulls, this is a fine compromise. > To keep backward compatibility we can create a implicit to convert > Option.None to nulls and Option.Some-> Option.get(), so you are not going > to break users who might have been using the APIs that were released in > 1.3. The current incompatibility is only this w.r.t. NDArrays. > > 2) Now about the Scala Macros - they are not simple to read or use, When I > and Qing started working on the #Scala Macros to improve the APIs, it took > us a good amount of time to get a hang of it. I don't want to add > additional code when not necessary. > > My suggestion and vote is to modify existing Macro(i.e., #1 from the > original email with the necessary clarification above) and make it > compatible with Java > Here are my reasons > 1) The NDArray APIs in question are not following functional style of > programming, in fact they are just static methods defined on an NDArray > object - so Scala users are not losing much by using null in place of None. > You can create a implicit to maintain backward compatibility > 2) It is adding 220+ APIs(I understand it is generated) for NDArray alone > 3) this is adding another 100s of APIs unnecessarily, we are starting with > NDArray but we can't stop there, we will have to do this for Symbol, > Executor, Iterators, etc., . > 3) I don't want to be fixing bugs and maintaining code in 2 places. > 4) I want the cryptic code(# scala macros) to a minimum. > 5) increased compilation time & bad developer experience - the time to > compile has gone up quite a bit since we added the APIs last release on my > 3 year old laptop already.. I think adding 400+ APIs unnecessarily would > significantly increase build time and bad developer experience > 6) I want to keep the core of the framework to be in Scala - because it > allows you to write concise code - Yes it has a bit of learning curve, not > everyone needs to know. I would rather invest in solidifying the Scala APIs > and add more features in Scala(RNN, Support GluonHybridizedBlock...there is > quite bit of work ) - do you want to rewrite everything in Scala and Java. > 7) Also, the discussion is not creating NDArray class for Java, just > generate certain APIs to cater for Java incompatibility. > > @Andrew: To your response to Qing's comments - you cannot just consider it > as just generating NDArray's APIs and instead I suggest to take a wholistic > view of all the various implications. > > @Chris: Yes, Scala has a bit of learning curve - the goal is not having > every developer to deal with how these APIs are generated, > the problem exists either ways with the above proposal. I might agree if we > were to move away completely(with a thorough discussion and valid reasons) > and instead use AspectJ or similar to write these APIs, the discussion is > about using Scala Macros to generate 2 different types of APIs which are > functionally not different and usability wise are very very similar, look > at the example. > Thanks for your input, I will deposit your 0.02$ in our JIRA bank :) > > @Carin: It requires more effort to use AspectJ or similar to generate APIs > using reflection or at compile time, here we need to generate at compile > time so Java users have the API signature on their IDEs. > > Thanks, Naveen > > P.S: I am traveling and my responses will be delayed. > > > On Fri, Sep 28, 2018 at 10:25 AM Carin Meier <carinme...@gmail.com> wrote: > > > Sorry bad paste on the gist - here is the good one > > https://gist.github.com/gigasquid/01cd48f563db4739910592dd9ac9db20 > > > > On Fri, Sep 28, 2018 at 10:24 AM Carin Meier <carinme...@gmail.com> wrote: > > > > > +1 on option #2 > > > > > > In the case of minimizing the the overhead for code maintenance, I wanted > > > to suggest the option of investigating generating code from the Java > > > Reflection for the Java APIs. I did a quick gist from Clojure of what > > the > > > generated classes look like from the current Scala Symbol.api for > > > FullyConnected here > > > https://gist.github.com/gigasquid/01cd48f563db4739910592 > > > > > > I looks like that there is always a base Java class generated will all > > the > > > arguments. If this is the case, then there is a possibility to generate a > > > Java api based on this Java method automatically with just a conversion > > for > > > the Scala option and it might be reusable for all the packages. > > > > > > Not sure if it will work for this use case, but thought I would bring it > > > up in case it's helpful. > > > > > > - Carin > > > > > > On Fri, Sep 28, 2018 at 7:05 AM Davydenko, Denis <d...@amazon.com.invalid > > > > > > wrote: > > > > > >> +1 on option #2. Having clear Java interface for NDArray, from my > > >> perspective, would be a better experience for Java users as it won't > > >> require them to deal with Scala code in any capacity. Overhead of extra > > >> code for additional macros is justified, in my mind, as it will be > > >> introduced with option #1 either way, just in a different place. > > >> > > >> -- > > >> Thanks, > > >> Denis > > >> > > >> On 9/27/18, 6:14 PM, "YiZhi Liu" <eazhi....@gmail.com> wrote: > > >> > > >> I vote for "2.) Leave the existing macro in place and add another > > >> which generates a Java friendly version" > > >> > > >> @Qing @Andrew, could you give some examples, so that people can > > better > > >> understand how it provides "best possible experience" to Java users. > > >> > > >> I have no strong preference between having JavaShape & JavaContext > > or > > >> not. > > >> On Thu, Sep 27, 2018 at 5:56 PM Andrew Ayres < > > >> andrew.f.ay...@gmail.com> wrote: > > >> > > > >> > That's not really the conversation I'm wanting to have. I want a > > >> discussion > > >> > about the macros with respect to NDArray so that we can get > > >> agreement on > > >> > our path forward with respect to implementing the NDArray wrapper. > > >> > > > >> > The design that was put forth and agreed to was for a a Java > > >> wrapper around > > >> > the Scala API. Adding a bunch of Java friendly methods inside the > > >> Scala > > >> > code would create a mess for users. Maintenance would be > > >> essentially the > > >> > same for both because either way you're going to be updating Java > > >> methods > > >> > when you make Scala changes. > > >> > > > >> > Let's please stick with the issue in the original email. > > >> > > > >> > Thanks, > > >> > Andrew > > >> > > > >> > On Thu, Sep 27, 2018 at 5:22 PM Qing Lan <lanking...@live.com> > > >> wrote: > > >> > > > >> > > I would like to loop this back a layer. Current, there is a > > >> discussion in > > >> > > the MXNet Scala community on the ways to implement the Java > > APIs. > > >> Currently > > >> > > there are two thoughts: > > >> > > > > >> > > 1. Make Scala Java Friendly (Create Java compatible methods in > > >> the Scala > > >> > > Class. such as NDArray with Java compatible constructor) > > >> > > 2. Make Java friendly wrappers in Scala (Andrew's explanation > > >> below) > > >> > > > > >> > > The first approach require minimum input from our side to > > >> implement > > >> > > however bring user a bunch of useless api they may not want to > > >> use. It also > > >> > > makes Scala package heavier. The good thing is these two > > packages > > >> require > > >> > > minimum maintenance cost. As a tradeoff, if any time in the > > >> future we want > > >> > > to make Java big (make Java as the primary language supported by > > >> MXNet), > > >> > > then the migration from Scala to Java will be harmful. Spark > > >> consider this > > >> > > carefully and decide not to change much on their Scala code base > > >> to make it > > >> > > more Java. > > >> > > > > >> > > The second approach will make unique NDArray, Shape, Context and > > >> more. The > > >> > > good thing about this is we can always holds a version control > > on > > >> Java. > > >> > > Some breaking changes on Scala may not influence much on Java. > > It > > >> did the > > >> > > best way to decouple the module and good for us to build unique > > >> pipeline > > >> > > for Java. The bad thing with this design is the maintenance cost > > >> as we need > > >> > > to keep two code bases, but it also make Java side easy to > > change > > >> to make > > >> > > it better compatible with users. > > >> > > > > >> > > Thanks, > > >> > > Qing > > >> > > > > >> > > On 9/27/18, 3:25 PM, "Andrew Ayres" <andrew.f.ay...@gmail.com> > > >> wrote: > > >> > > > > >> > > Hi, > > >> > > > > >> > > Currently, we're working to implement a new Java API and > > >> would like > > >> > > some > > >> > > feedback from the community on an implementation detail. In > > >> short, the > > >> > > new > > >> > > Java API will use the existing Scala API (in a manner > > similar > > >> to how > > >> > > the > > >> > > current Clojure API works). This basically means that we're > > >> making Java > > >> > > friendly wrappers to call the existing Scala API. > > >> > > > > >> > > The feedback we're looking for is on the implementation of > > >> NDArray. > > >> > > Scala's > > >> > > NDArray has a significant amount of code which is generated > > >> via macros > > >> > > and > > >> > > we've got two viable paths to move forward: > > >> > > > > >> > > 1.) Change the macro to generate Java friendly methods - To > > >> do this > > >> > > we'll > > >> > > modify the macro so that the generated methods won't have > > >> > > default/optional > > >> > > arguments. There may also have to be some changes to > > >> parameter types to > > >> > > make them Java friendly. The big advantage here is that > > >> ongoing > > >> > > maintenance > > >> > > will easier. The disadvantages are that we'll be changing > > the > > >> existing > > >> > > Scala NDArray Infer API (it's marked experimental) and Scala > > >> users will > > >> > > lose the ability to use the default and optional arguments. > > >> > > > > >> > > 2.) Leave the existing macro in place and add another which > > >> generates a > > >> > > Java friendly version - The biggest issue here is that we'll > > >> be > > >> > > doubling > > >> > > the number of macros that we've got to maintain. It'll > > become > > >> even more > > >> > > overhead once we start expanding the Java API with more > > >> classes that > > >> > > use > > >> > > generated code like this. The advantages are that the > > >> existing Scala > > >> > > NDArray Infer API would remain unchanged for Scala users and > > >> that the > > >> > > new > > >> > > macro could be optimized to give the best possible > > experience > > >> to the > > >> > > Java > > >> > > API. > > >> > > > > >> > > Thanks, > > >> > > Andrew > > >> > > > > >> > > > > >> > > > > >> > > >> > > >> > > >> -- > > >> Yizhi Liu > > >> DMLC member > > >> Amazon Web Services > > >> Vancouver, Canada > > >> > > >> > > >> > > -- Yizhi Liu DMLC member Amazon Web Services Vancouver, Canada
