Call for Discussion: New Project: Babylon

Call for Discussion: New Project: Babylon<br />

Paul Sandoz
paul.sandoz at

Wed Sep 6 16:42:53 UTC 2023

I hereby invite discussion of a new Project, Babylon, whose primary goal
will be to extend the reach of Java to foreign programming models such as 
SQL, differentiable programming, machine learning models, and GPUs.

Focusing on the last example, suppose a Java developer wants to write a GPU 
kernel in Java and execute it on a GPU. The developer’s Java code must, 
somehow, be analyzed and transformed into an executable GPU kernel. A Java 
library could do that, but it requires access to the Java code in symbolic 
form. Such access is, however, currently limited to the use of non-standard 
APIs or to conventions at different points in the program’s life cycle 
(compile time or run time), and the symbolic forms available (abstract 
syntax trees or bytecodes) are often ill-suited to analysis and transformation.

Babylon will extend Java's reach to foreign programming models with an 
enhancement to reflective programming in Java, called code reflection. This 
will enable standard access, analysis, and transformation of Java code in a 
suitable form. Support for a foreign programming model can then be more 
easily implemented as a Java library.

Babylon will ensure that code reflection is fit for purpose by creating a 
GPU programming model for Java that leverages code reflection and is 
implemented as a Java library. To reduce the risk of bias we will also 
explore, or encourage the exploration of, other programming models such as 
SQL and differentiable programming, though we may do so less thoroughly.

Code reflection consists of three parts:

1) The modeling of Java programs as code models, suitable for access,
   analysis, and transformation.
2) Enhancements to Java reflection, enabling access to code models at compile
   time and run time.
3) APIs to build, analyze, and transform code models.

For further details please see the JVM Language Summit 2023 presentations 
entitled "Code Reflection" [1] and "Java and GPU … are we nearly there yet?" 

I propose to lead this Project with an initial set of Reviewers that
includes, but is not limited to, Maurizio Cimadamore, Gary Frost, and
Sandhya Viswanathan.

For code reflection this Project will start with a clone of the current JDK 
main-line release, JDK 22, and track main-line releases going forward.
For the GPU programming model this Project will create a separate repository,
that is dependent on code reflection features as they are developed.

We expect to deliver Babylon over time, in a series of JEPs that will likely
span multiple feature releases.
We do not currently plan to deliver the GPU programming model into the JDK.
However, work on that model could identify JDK features and enhancements of 
general utility which could be addressed in future work.




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