C2ME — Multithreaded Chunk Generation for Minecraft

C2ME — Multithreaded Chunk Generation for Minecraft

C2ME (Concurrent Chunk Management Engine) speeds up chunk generation, loading, and saving. Vanilla Minecraft runs world generation mostly on a single thread, so on a multi-core CPU most cores sit idle while you explore new territory. C2ME parallelizes this work across every available core. The biggest gain shows up during new chunk generation: flying over the map, running Chunky, or starting a server on a fresh world.

What C2ME Speeds Up

The mod rewrites three areas of chunk handling: generation (worldgen), loading from disk, and saving to disk (I/O). All three now run in parallel across multiple threads instead of just one. The clearest metric is chunks per second (cps) — how many chunks get generated each second. Vanilla hits a ceiling of around 13–14 cps regardless of core count, since it doesn't scale; C2ME scales almost linearly with thread count.

Author's benchmarks on a server-grade Xeon Gold 5218R (capped at 2 GHz), generating with the Terralith datapack:

At 16 threads, C2ME hits about 184 cps versus 14 for vanilla — roughly 13x faster. Paper is also multithreaded but scales worse, capping out around 77 cps at 16 threads.

Preserving Vanilla Behavior

C2ME doesn't change the world generation logic itself for the sake of speed — structures, biomes, and ores generate exactly as they do in vanilla. However, due to vanilla generation's known non-determinism (bug MC-55596), worlds with the same seed can differ between runs — this is the game's own behavior, not the mod's.

Configuration

Settings live in the c2me.toml file inside the config folder. The key parameter is globalExecutorParallelism — the number of threads the mod dedicates to generation. By default it's picked automatically; for maximum flyover speed, set it to your CPU's core count.

Conclusion

C2ME covers multithreaded chunk generation — something neither Lithium (game logic) nor Sodium (rendering) does. The biggest winners are servers and singleplayer worlds on many-core CPUs during exploration of new territory or pre-generation with Chunky. On an already-generated world, where chunks are just loaded from disk, the gain is smaller. Limitations: Fabric only (NeoForge has a separate build), full support only for the latest release and snapshot, with older versions getting critical fixes only. A world backup before installing is mandatory.

FAQ

What does C2ME do? It speeds up chunk generation, loading, and saving by using multiple CPU cores. The effect is most noticeable during generation of new territory.

Does C2ME speed up an already-generated world? To a lesser extent. The main gain comes from generating new chunks. On an old world, chunks are simply read from disk, so the improvement is more modest.

What mods should I pair with C2ME? The author recommends Lithium and ScalableLux. Their scopes don't overlap: C2ME handles chunks, Lithium handles logic, ScalableLux handles lighting.

Does C2ME change world generation? No. Worldgen logic stays vanilla. Differences between worlds with the same seed come from the game's own non-determinism (bug MC-55596), not the mod.

Which loaders does C2ME support? This version is for Fabric; NeoForge has a separate C2ME build. There is no Forge version.