Hi, Joern, when you say "Java API " it's sharing scala impl or not?
Best, Nan On Wed, Aug 16, 2017 at 12:46 PM, Joern Kottmann <kottm...@gmail.com> wrote: > Seems like we are all agree about the idea to add a Java API. > > Maybe it is just me, but it wouldn't at all make sense for me (OpenNLP > use case) to use the Java API when it requires a Scala dependency, > because at that point I would be better of just using the Scala API, > and ensure that the things I build are compatible with Java. > > So if I don't want to add Scala as a dependency then I am better off > building something on top of a generated JNI layer. As far as I can > tell from my tests with the scala-package you can get quite far with > MXNet using NDArray and the Symbol API. > > Maybe we could work on this from two sides as described by Pracheer. > If we have a well defined Java API you could look at the work I have > done by then and see how it can be plugged in or what can be learnt > from it. > > Jörn > > On Wed, Aug 16, 2017 at 9:05 PM, Nan Zhu <zhunanmcg...@gmail.com> wrote: > > +1 for Sandeep's suggestion > > > > On Wed, Aug 16, 2017 at 11:21 AM, YiZhi Liu <javeli...@gmail.com> wrote: > > > >> Agree with Sandeep, while I guess the performance won't change. But > >> yes, benchmark talks. > >> > >> Moreover, in Scala package we use macros to generate operators > >> automatically, which will require more efforts if we switch to pure > >> Java. > >> > >> 2017-08-17 2:12 GMT+08:00 sandeep krishnamurthy < > >> sandeep.krishn...@gmail.com>: > >> > The fastest way to get Java binding is through building Java native > >> > wrappers on Scala package. > >> > Disadvantages would be: > >> > * *Bloated library size: *May not be suitable for users planning to > >> use > >> > Java APIs in Android of such smaller systems. > >> > * *Performance:* Performance may not be as good as building > directly > >> > over JNI and implementing ground up. For example, taking NDArray > >> dimensions > >> > as Java ArrayList then converting it to Scala Seq to adapt for Scala > >> > NDArray API and more such adapters. > >> > > >> > However, building ground up from JNI would be a huge effort without > >> > actually getting feedback from users early. > >> > > >> > *My Plan:* > >> > 1. Build Java interface on top of Scala package. > >> > 2. Get early feedback from users. It may turn out Java is not a great > >> > candidate for DL training jobs. > >> > 3. Solidify the interface (APIs) for Java users. > >> > 4. Do performance benchmarks to see Scala Native / Java interface. > This > >> > gives us comparable numbers on performance in Java. > >> > 5. Over a period of time replace underlying Scala usage with JNI base > and > >> > native Java implementation. Provided feedback from users is positive. > >> > > >> > Comments/Suggestion? > >> > > >> > Regards, > >> > Sandeep > >> > > >> > > >> > On Wed, Aug 16, 2017 at 10:56 AM, YiZhi Liu <javeli...@gmail.com> > wrote: > >> > > >> >> What Nan and I worried about is the re-implementation of something > >> >> like https://github.com/apache/incubator-mxnet/blob/master/ > >> >> scala-package/core/src/main/scala/ml/dmlc/mxnet/Model.scala#L246, > >> >> and the executorManager, NDArray, KVStore ... it uses. > >> >> > >> >> the C API stays at the very low level. If this is the purpose, we can > >> >> simply move ml.dmlc.mxnet.LibInfo to 'java' folder and compile > without > >> >> scala, no need to introduce JavaCPP. But I don't think this is what > >> >> users want. > >> >> > >> >> 2017-08-17 1:41 GMT+08:00 Joern Kottmann <kottm...@gmail.com>: > >> >> > There will be a new scala version one day, and the story we had > with > >> >> > going from 2.10 to 2.11 might just repeat. In the end if you make a > >> >> > dependency using scala you just end up making it for the currently > >> >> > popular scala versions. And that might be ok for projects with > >> >> > developers who are familiar with these issues, but it is not ok for > >> >> > java projects, where people might not expect it or know about these > >> >> > problems. It just makes it harder to use. > >> >> > > >> >> > To me it looks like that the C API is very stable and used by > all/most > >> >> > other APIs. If we have a Java API - accessing the C API via > JavaCPP - > >> >> > then we should end up with a pretty stable solution and a lot the > code > >> >> > that is duplicated with the Scala API is the generated code. > >> >> > > >> >> > I think we should explore this possible way of implementing it > with a > >> >> > proof-of-concept. > >> >> > > >> >> > And if we have a well made Java API it might be something which > maybe > >> >> > wouldn't need a lot of additions to be pleasurable to use from > scala. > >> >> > > >> >> > Jörn > >> >> > > >> >> > On Wed, Aug 16, 2017 at 6:45 PM, Nan Zhu <zhunanmcg...@gmail.com> > >> wrote: > >> >> >> I don't think there will be problems under "11", did the user see > >> >> concrete > >> >> >> errors? > >> >> >> > >> >> >> Best, > >> >> >> > >> >> >> Nan > >> >> >> > >> >> >> > >> >> >> > >> >> >> On Wed, Aug 16, 2017 at 9:30 AM, YiZhi Liu <javeli...@gmail.com> > >> wrote: > >> >> >> > >> >> >>> Hi Nan, > >> >> >>> > >> >> >>> Users have 2.11, but with a different minor version, will it > cause > >> >> >>> conflicts? > >> >> >>> > >> >> >>> 2017-08-17 0:19 GMT+08:00 Nan Zhu <zhunanmcg...@gmail.com>: > >> >> >>> > Hi, Yizhi, > >> >> >>> > > >> >> >>> > You mean users have 2.10 env while we assemble 2.11 in it? > >> >> >>> > > >> >> >>> > Best, > >> >> >>> > > >> >> >>> > Nan > >> >> >>> > > >> >> >>> > On Wed, Aug 16, 2017 at 9:08 AM, YiZhi Liu < > javeli...@gmail.com> > >> >> wrote: > >> >> >>> > > >> >> >>> >> Hi Joern, > >> >> >>> >> > >> >> >>> >> The point is that, the front is not a simple wrapper of > c_api.h, > >> as > >> >> >>> >> you mentioned, which can be easily achieved by JavaCPP. > >> >> >>> >> > >> >> >>> >> I have noticed the potential conflicts between the assembled > >> scala > >> >> >>> >> library and the one in users' environment. Can we remove the > >> scala > >> >> >>> >> library from the assembly jar? @Nan It wouldn't be a problem > >> since > >> >> the > >> >> >>> >> scala libraries with same major version are compatible. > >> >> >>> >> > >> >> >>> >> 2017-08-16 23:49 GMT+08:00 Joern Kottmann <kottm...@gmail.com > >: > >> >> >>> >> > Hello, > >> >> >>> >> > > >> >> >>> >> > I personally had quite some issues with Scala dependencies > in > >> >> >>> >> > different versions and Spark, where one version is not > >> compatible > >> >> with > >> >> >>> >> > the other version. Then you need to debug the dependency > tree > >> to > >> >> find > >> >> >>> >> > the places where the versions don't match. Every project > which > >> >> would > >> >> >>> >> > like to use MXnet then has to depend on Scala and might also > >> get > >> >> >>> >> > conflicts if other dependencies depend on different Scala > >> >> versions. > >> >> >>> >> > Probably something which will cause issues for some of your > >> users. > >> >> >>> >> > Users who want to use Java might not be familiar with Scala > >> >> dependency > >> >> >>> >> > problems and have a hard time resolving them by getting > strange > >> >> error > >> >> >>> >> > messages. > >> >> >>> >> > > >> >> >>> >> > The JNI layer could be generated with JavaCPP, then we would > >> not > >> >> need > >> >> >>> >> > to write/maintain the C and the jvm side for that our self. > >> >> >>> >> > A good example of JavaCPP and Scala usage is Apache Mahout > [1]. > >> >> >>> >> > > >> >> >>> >> > Even if we don't use JavaCPP, the JNI layer should be easy > to > >> get > >> >> into > >> >> >>> >> > a state where both can share it, the current Scala JNI > layers > >> >> LibInfo > >> >> >>> >> > classes could be converted to Java classes and would in most > >> cases > >> >> >>> >> > require only minor changes in the Scala code. > >> >> >>> >> > > >> >> >>> >> > Jörn > >> >> >>> >> > > >> >> >>> >> > [1] https://github.com/apache/mahout/tree/master/viennacl/ > >> >> src/main > >> >> >>> >> > > >> >> >>> >> > On Wed, Aug 16, 2017 at 5:30 PM, Nan Zhu < > >> zhunanmcg...@gmail.com> > >> >> >>> wrote: > >> >> >>> >> >> I agree with Yizhi > >> >> >>> >> >> > >> >> >>> >> >> My major concern is the duplicate implementations, which > are > >> >> usually > >> >> >>> >> one of > >> >> >>> >> >> the major sources of bugs, especially with two languages > which > >> >> are > >> >> >>> >> >> naturally interactive (OK, Calling Scala from Java might > need > >> >> some > >> >> >>> more > >> >> >>> >> >> efforts). It is just like we provide C++ & C APIs of MxNet > in > >> two > >> >> >>> >> separated > >> >> >>> >> >> packages. > >> >> >>> >> >> > >> >> >>> >> >> About dependency problem, when you say "As far as I see > this > >> has > >> >> the > >> >> >>> >> great > >> >> >>> >> >> disadvantage that the Java API would force Scala as a > >> dependency > >> >> onto > >> >> >>> >> the > >> >> >>> >> >> java users.", would you please give a concrete example > causing > >> >> >>> critical > >> >> >>> >> >> issues? > >> >> >>> >> >> > >> >> >>> >> >> Best, > >> >> >>> >> >> > >> >> >>> >> >> Nan > >> >> >>> >> >> > >> >> >>> >> >> > >> >> >>> >> >> > >> >> >>> >> >> On Wed, Aug 16, 2017 at 8:19 AM, YiZhi Liu < > >> javeli...@gmail.com> > >> >> >>> wrote: > >> >> >>> >> >> > >> >> >>> >> >>> Hi, > >> >> >>> >> >>> > >> >> >>> >> >>> If we build the Java API from the very beginning, i.e. the > >> JNI > >> >> part, > >> >> >>> >> >>> we have to rewrite the codes for training, predict, > >> inferShape, > >> >> etc. > >> >> >>> >> >>> It would be too heavy to maintain a totally new front > >> language. > >> >> >>> >> >>> > >> >> >>> >> >>> As far as I see, I don't think Scala library dependency > would > >> >> be a > >> >> >>> big > >> >> >>> >> >>> problem in most cases, unless we are going to use it in > >> embedded > >> >> >>> >> >>> devices. Could you illustrate some use-cases where you > cannot > >> >> >>> involve > >> >> >>> >> >>> Scala dependencies? > >> >> >>> >> >>> > >> >> >>> >> >>> 2017-08-16 22:13 GMT+08:00 Joern Kottmann < > >> kottm...@gmail.com>: > >> >> >>> >> >>> > Hello, > >> >> >>> >> >>> > > >> >> >>> >> >>> > the approach which is taken by Spark is described here > [1]. > >> >> >>> >> >>> > > >> >> >>> >> >>> > As far as I see this has the great disadvantage that the > >> Java > >> >> API > >> >> >>> >> >>> > would force Scala as a dependency onto the java users. > >> >> >>> >> >>> > For a library it is always a great advantage if it > doesn't > >> >> have > >> >> >>> many > >> >> >>> >> >>> > dependencies, or zero dependencies. In our case it > could be > >> >> quite > >> >> >>> >> >>> > realistic to have a thin wrapper around the C API > without > >> >> needing > >> >> >>> any > >> >> >>> >> >>> > other dependencies (or only dependencies which can't be > >> >> avoided). > >> >> >>> >> >>> > > >> >> >>> >> >>> > The JNI layer could easily be shared between the Java > and > >> >> Scala > >> >> >>> API. > >> >> >>> >> >>> > As far as I understand is the JNI layer in the Scala API > >> >> anyway > >> >> >>> >> >>> > private and a change to it wouldn't require that the > public > >> >> part > >> >> >>> of > >> >> >>> >> >>> > the Scala API is changed. > >> >> >>> >> >>> > > >> >> >>> >> >>> > What do you think? > >> >> >>> >> >>> > > >> >> >>> >> >>> > Jörn > >> >> >>> >> >>> > > >> >> >>> >> >>> > [1] https://cwiki.apache.org/ > >> confluence/display/SPARK/Java+ > >> >> >>> >> API+Internals > >> >> >>> >> >>> > > >> >> >>> >> >>> > On Wed, Aug 16, 2017 at 3:39 PM, YiZhi Liu < > >> >> javeli...@gmail.com> > >> >> >>> >> wrote: > >> >> >>> >> >>> >> Hi Joern, > >> >> >>> >> >>> >> > >> >> >>> >> >>> >> I suggest to build Java API as a wrapper of Scala API, > >> re-use > >> >> >>> most > >> >> >>> >> of > >> >> >>> >> >>> >> the procedures. Referring to the Java API in Apache > Spark. > >> >> >>> >> >>> >> > >> >> >>> >> >>> >> 2017-08-16 18:21 GMT+08:00 Joern Kottmann < > >> jo...@apache.org > >> >> >: > >> >> >>> >> >>> >>> Hello all, > >> >> >>> >> >>> >>> > >> >> >>> >> >>> >>> I would like to propose the addition of a Java API to > >> MXNet. > >> >> >>> >> >>> >>> > >> >> >>> >> >>> >>> There has been some previous work done for the Scala > API, > >> >> and it > >> >> >>> >> makes > >> >> >>> >> >>> >>> sense to at least share the JNI layer between the two. > >> >> >>> >> >>> >>> > >> >> >>> >> >>> >>> The Java API probably should be aligned with the > Python > >> API > >> >> >>> (and > >> >> >>> >> >>> >>> others which exist already) with a few changes to give > >> it a > >> >> >>> native > >> >> >>> >> >>> >>> Java feel. > >> >> >>> >> >>> >>> > >> >> >>> >> >>> >>> As far as I understand there are multiple people > >> interested > >> >> to > >> >> >>> >> work on > >> >> >>> >> >>> >>> this and it would be good to maybe come up with a > written > >> >> >>> proposal > >> >> >>> >> on > >> >> >>> >> >>> >>> how things should be. > >> >> >>> >> >>> >>> > >> >> >>> >> >>> >>> My motivation is to get a Java API which can be used > by > >> >> Apache > >> >> >>> >> OpenNLP > >> >> >>> >> >>> >>> to solve various NLP tasks using Deep Learning based > >> >> approaches > >> >> >>> >> and I > >> >> >>> >> >>> >>> am also interested to work on MXNet. > >> >> >>> >> >>> >>> > >> >> >>> >> >>> >>> Jörn > >> >> >>> >> >>> >> > >> >> >>> >> >>> >> > >> >> >>> >> >>> >> > >> >> >>> >> >>> >> -- > >> >> >>> >> >>> >> Yizhi Liu > >> >> >>> >> >>> >> DMLC member > >> >> >>> >> >>> >> Technical Manager > >> >> >>> >> >>> >> Qihoo 360 Inc, Shanghai, China > >> >> >>> >> >>> > >> >> >>> >> >>> > >> >> >>> >> >>> > >> >> >>> >> >>> -- > >> >> >>> >> >>> Yizhi Liu > >> >> >>> >> >>> DMLC member > >> >> >>> >> >>> Technical Manager > >> >> >>> >> >>> Qihoo 360 Inc, Shanghai, China > >> >> >>> >> >>> > >> >> >>> >> > >> >> >>> >> > >> >> >>> >> > >> >> >>> >> -- > >> >> >>> >> Yizhi Liu > >> >> >>> >> DMLC member > >> >> >>> >> Technical Manager > >> >> >>> >> Qihoo 360 Inc, Shanghai, China > >> >> >>> >> > >> >> >>> > >> >> >>> > >> >> >>> > >> >> >>> -- > >> >> >>> Yizhi Liu > >> >> >>> DMLC member > >> >> >>> Technical Manager > >> >> >>> Qihoo 360 Inc, Shanghai, China > >> >> >>> > >> >> > >> >> > >> >> > >> >> -- > >> >> Yizhi Liu > >> >> DMLC member > >> >> Technical Manager > >> >> Qihoo 360 Inc, Shanghai, China > >> >> > >> > > >> > > >> > > >> > -- > >> > Sandeep Krishnamurthy > >> > >> > >> > >> -- > >> Yizhi Liu > >> DMLC member > >> Technical Manager > >> Qihoo 360 Inc, Shanghai, China > >> >
