Jacobin JVM at 18 months

Earlier this month, the Jacobin JVM project (a JVM written in Go) reached its 18-month milestone. Since our post at the 12-month mark, we have added support for numerous Java bytecodes to the interpreter, including all the bytecodes for longs, floats, doubles and their operations, all the bit manipulations, and all operations on single-dimensional arrays of primitives. We've implemented 176 bytecodes at present and expect to finish up the remaining ones we need during the coming six months.

At present, Jacobin can execute simple static classes, which is enough to allow us to test functionality and to begin running benchmarks. While performance has not in any way been a goal during our work, as we get closer to finishing the interpreter, it will assume greater importance. @suresk is already sketching out an observability client, similar to VisualVM and other tools, to guide our optimization work. 

Jacobin continues to meet our initial goals: it is written entirely in Go and has no dependencies. It runs fast and the executable is only 3.1MB (on Windows). It runs Java class files and JARs compiled by Java 7 through Java 17.

By the numbers

Jacobin's codebase consists of 25,813 lines (which include code, comments, and blank lines). As mentioned in earlier posts, we have a very deep commitment to testing as shown by the fact that this codebase includes 18,015 lines of testing code for the 7,798 of production code. This is a ratio of testing code to production code of 2.31x -- our highest to date (as we set out to do in earlier posts). Those 18K lines represent 429 unit and integration tests.

Easy Things You Can Do to Help

While Jacobin is still in pre-alpha mode, if you choose to build it or run one of the posted executables on GitHub, we’d love your feedback. We respond quickly to any and all feedback and questions. In this regard, Richard Elkins (@texadactyl) deserves our heartfelt thanks for running Jacobin on various test files and sharing his results with us.

If you’d just like to show your support for the project, we'd love a star on GitHub. Knowing people are interested in Jacobin really helps keep our motivation and spirits high. If you're on Twitter, please follow our handle (@jacobin_jvm) to keep abreast of what we’re doing.