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From Luciano Resende <>
Subject Re: Discussion SYSTEMML-593 MLContext Resign
Date Sun, 03 Apr 2016 05:20:06 GMT
On Sat, Apr 2, 2016 at 9:34 PM, Matthias Boehm <> wrote:

> thanks Deron for initiating the discussion around the rework of our
> MLContext API ( Here
> are a couple of thoughts:
> (1) Simplicity: Given that the primary usecase of MLContext calls a script
> exactly once, I'm wondering if the separation into Script, ScriptFactory,
> ScriptExecutor and MLContext adds unnecessary complexity by requiring more
> code to setup. It would be great to see old vs new examples side by side.
> Also rather than introducing another exception class, couldn't we just
> reuse DMLException by making it an uncaught exception?

Simplicity and easy of use will, in my view, dictate use adoption. One way
I usually do to accomplish this is to start by building an app or test
scenario and use that to model the user experience when using the APIs.
This might help identify how many steps the user needs to handle before
actually using the api (e.g. Script, ScriptFactory, etc) and if those steps
are really necessary... But, to be successful with this approach, you
really need to come with a clean mind, and really think as a user trying to
use the API.

Having said that, sometimes we do need a fine grained api, but sometimes
that might be used internally (private apis) and be exposed to the user
with a more coarse grained api that hides much of the details and expose a
simple programming model to the user.

Also, I like the option to have a fluent API, which makes the code more
readable and easy to use.

> (2) Compilation: ScriptExecutor would also be yet another replicate of our
> compilation chain (beside DMLScript, Debugger, JMLC, MLContext). Please,
> keep in mind that we are about to consolidate this, centralizing these
> calls via a configurable compilation chain because it really becomes a
> maintenance nightmare (as recently seen when we reworked our thread-local
> configuration management).
> (3) Data Representation / Converters: Making data conversions and
> input/output handling easier is certainly useful. However, isn't this new
> class hierarchy redundant to our already existing hierarchy of Data,
> MatrixObject, FrameObject, and ScalarObject?

Is there a way to hide some of the input/output registration calls by some
convention over api calls ?

> (4) Consolidating MLContext and JMLC: This is a good idea since MLContext
> is anyway "derived" from JMLC and both rely on the same concepts for
> input/output handling and program modification (see JMLCUtils). Down the
> road I would like to see a convergence to something like Script and
> PreparedScript in the spirit of JDBC's Statement and PreparedStatement
> (btw, that's how we created JMLC). Let's keep in mind that there are
> already a number of users working against both MLContext and JMLC, so we
> should support them separately until our major 1.0 release.
> Regards,
> Matthias

Luciano Resende

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