v4.1.0

v4.1.0

May 28, 2026 · GitHub ↗

Java. That's the headline.

gempba is now a Maven dependency. Drop it into a pom.xml, write import io.gempba.*, and call the same scheduler family, load balancer, and node manager you would from C++ — just from Java this time. One fat JAR per flavor (mt, mp-mpi) carries the native binaries for Linux, Windows, and macOS inside the artifact, so there is no per-platform build dance, no classifier juggling, no "first set LD_LIBRARY_PATH" footnote. You add the dependency, you build, you run.

That this is shippable at all is because of the second piece of v4.1.0: a stable C ABI underneath. The Java binding is the first consumer of it, but the same headers are what any future Python / Rust / .NET binding will sit on. If you have a JVM pipeline, a Spark job, an Airflow operator, an enterprise application — anywhere C++ was the wrong language but you still wanted gempba's scheduler — that bridge now exists.

Everything else in v4.1.0 is the surrounding work: the publish pipeline, the README the new Java audience needs, a couple of bug fixes. No public C++ API changes — additive on top of v4.0.0.

Added

• Stable C ABI (<gempba/cabi/gempba.h>) — extern-C surface covering the full runtime: scheduler family, load balancer, node manager, factories, runnables, MP / MT entry points, per-node result retrieval. The same headers any non-C++ binding will reuse going forward (#185)
• Java JNI binding (io.gempba:gempba) — typed wrappers for Node, LoadBalancer, NodeManager, RankStats, Score / ScoreType, Goal, BalancingPolicy, the task / serializer / deserializer functional interfaces, the scheduler family (MP-only), and GemPBA entry points for both flavors (#186)
• Multi-platform fat JAR — each published JAR carries natives/<os>-<arch>/ for Linux x86_64, Windows x86_64, and macOS aarch64. NativeLoader picks the right binary at runtime, so the same JAR runs unchanged on any supported platform. No per-OS classifier, no platform-specific Maven profiles (#274)
• Maven publication to GitHub Packages on every v* tag, with classifiers mt (multithreading) and mp-mpi (multiprocessing). Add the repo to your settings.xml, declare the dependency with the classifier you want, build (#187)
• README "Maven dependency (Java)" subsection — repository + settings.xml + dependency snippet, plus a cutoff note that Maven artifacts start at v4.1.0 (earlier tags predate the publish flow). Platforms section gains a per-OS architecture table (#283)

Fixed

• default_mpi_stats_visitor::labels() was missing the total_thread_requests key — values were emitted but the label vector didn't cover them, breaking downstream consumers that zipped labels with values (#262)
• set_thread_pool_size could race against in-flight construction; the resize now round-trips a no-op task to fence the pool's worker threads before returning (#277)

Build

• CI workflows split into mutually exclusive triggers: ci-*.yml runs on PRs and branch pushes, release-*.yml runs on tags. Reusable building blocks factored out so tag-time publish reuses the exact build path CI exercises (#265)
• Workflow folder reorganized with ci- / release- prefixes, a .github/workflows/README.md, and shared composite actions extracted (#271)
• prepare-release.yml now bumps bindings/java/pom.xml's <version> alongside the CMake / PKGBUILD bumps so the Java release version stays in lockstep with the C++ release version (#187)
• Lint workflow bumped to LLVM 22; the modernizations clang-tidy 22 flagged were applied (#261)