Concurrent Chunk Management Engine – Forge

Concurrent Chunk Management Engine (Forge)

An unofficial Forge port of C2ME by ishland / RelativityMC, for Minecraft 1.20.1 and 1.18.2. Original mod: https://modrinth.com/mod/c2me-fabric

Minecraft generates, loads, saves and lights chunks on a single thread. On a modern multi-core CPU that means most of your cores sit idle while you stutter through fresh terrain. C2ME makes that work parallel. It is the engine behind smooth exploration and fast world pre-generation on Fabric, ported to classic Minecraft Forge.

This is a community port, not made or endorsed by the original C2ME team. All the hard engine work is theirs; this project carries it to Forge. Please report Forge-specific issues here, not to upstream C2ME.

Support & bug reports

**Join the Discord: https://discord.gg/s7BYs6Njj5**

This is where I handle issues, and it is by far the fastest way to reach me. Crashes, mod conflicts, questions about which version to run, or a pack that generates slower than you expect: post it there and I’ll take a look. Reports from real modpacks are how most of the compatibility fixes in this mod were found.

Bring your latest.log (or the crash report) plus the pack name and version.

What it does

• Multi-threaded world generation: terrain, biomes, features and structures generate across all your cores.
• Multi-threaded chunk I/O: loading and saving no longer stall the game thread.
• Multi-threaded lighting.
• No-tick view distance: see farther without ticking (and lagging) those chunks.
• Smarter scheduling and lower allocation overhead during world generation.
• Thread-safety fixes for a pile of vanilla and modded world generation bugs.

Ships as a single mod built from per-feature modules, each of which can be switched off on its own.

Performance

Every number on this page was measured on the files you can download here, at their default settings: no flags, no config edits, fresh world every run, same seed. Dedicated-server and singleplayer tests were run separately, never at the same time.

Test machine: Intel i9-9900K (8 cores / 16 threads), 32 GB RAM, Windows 10, 8 GB heap. Dedicated servers: Java 17 (1.18.2) and Java 21 (1.20.1); singleplayer: Java 17.

Minecraft 1.20.1

Vanilla world, dedicated server, /chunky radius 1000 (16,129 chunks): 3:28 without C2ME, 0:48 with C2ME: 4.3x faster (3 runs each).

Heavy modpacks, singleplayer: 2.8x to 4.3x faster.

Minecraft 1.18.2

The 1.18.2 build carries the modernized threading engine from the 1.20.1 line, newer than anything upstream C2ME shipped for 1.18.2, plus two things that matter on this version:

• Built-in Starlight light engine. On 1.18.2 the single-threaded light engine is the pre-generation bottleneck, so this build includes Starlight’s rewritten engine (Spottedleaf / PaperMC, LGPL-3.0; license and full module source included). It switches itself off if you already run standalone Starlight.
• Self-tuning world generation feed. It measures your hardware while generating and tunes itself as it goes: +58 % against the same jar with the auto-tune switched off.

Vanilla world, dedicated server, /chunky radius 1000: 4:29 without C2ME, 1:12 with C2ME: 3.7x faster (3 runs each). With C2ME-Betterlight: the same 1:12.

Heavy modpacks, singleplayer: 3.2x to 4.5x faster.

Thread-unsafe world generation mods are detected at load and contained automatically: one generation stage is serialized for the one mod that needs it, and everything else keeps generating in parallel. No commands, no config, no opt-in.

Five packs that once could not finish a pre-generation all pass a full /chunky radius 1000 today, with 0 C2ME crashes across 9 packs:

RAM

C2ME keeps many chunks in flight at once and sizes that to the heap it has, so heavy packs run well at 8 GB. More heap still helps a little (+7 % and +12 % at 12 GB in my tests):

C2ME-Betterlight (1.18.2, optional add-on)

[C2ME-Betterlight] replaces the built-in Starlight with C2ME’s own light engine, on the server and on the client. In my tests players saw 0 wrong light values in every run (Starlight showed 94 in one of five), and the worst frame at spawn was 28 % shorter, at the same FPS and pre-generation speed. It is a separate download made for one exact C2ME version (1.0.0 needs 0.2.0-forge.8.2). Without it nothing changes.

Requirements

• 1.20.1: Minecraft 1.20.1, Forge 47.x, Java 17 or newer
• 1.18.2: Minecraft 1.18.2, Forge 40.x, Java 17

Download the file that matches your Minecraft version; they are separate builds.

Compatibility

C2ME is built to sit alongside the usual Forge performance stack: Embeddium, ModernFix, FerriteCore, ServerCore, Canary and more. When another mod already optimizes the same code (Canary, Radium and other Lithium forks), C2ME steps aside for just those overlapping pieces, while its multi-threaded generation keeps running on top. Known conflicts with mods like NBTac, LongNbtKiller and MoreMobVariants are handled the same way, no config needed.

• Arclight (1.20.1 Forge + Bukkit hybrid servers) works since forge.9.9.4.
• Architectury and other library mods are part of every release test.
• Thread-unsafe world generation mods (for example Lost Cities, Blueprint mods, Large Ore Deposits, Skyblock Builder, Ore Tweaker) are recognised at load, and only the stage each one is unsafe in gets serialized. Hit one I don’t know about yet? Bring the log to Discord and it will be added.

If you already run Canary or ServerCore, C2ME’s biggest addition is the threaded world generation they don’t provide.

Configuration

• Settings live in config/c2me.toml. You should not need to change anything.
• Any module can be switched off with a JVM flag: -Dc2me.disableModule.MODULE=true (e.g. -Dc2me.disableModule.opts.scheduling=true).
• Commands: /c2me notick (no-tick view distance status; operators only).

Known notes

• Needs adequate RAM: see Performance.
• Because it replaces the chunk-storage backend, a few mods that reach directly into vanilla chunk-storage internals may need per-mod tweaks. Please report any you hit on Discord: https://discord.gg/s7BYs6Njj5

Credits & license

Original C2ME (c) 2021-2024 ishland and RelativityMC. Source: https://github.com/RelativityMC/C2ME-fabric Licensed under the MIT License; this port is redistributed under the same license, with the full notice included in the jar. Huge thanks to the C2ME team: this port exists only because of their work.

The 1.18.2 build additionally includes the Starlight light engine, (c) Spottedleaf and the PaperMC project, licensed under LGPL-3.0. Its license is included in the jar, and the complete corresponding source of that module is published here: https://gitlab.com/thescriptersdk/starlight-c2me-source Upstream Starlight: https://github.com/PaperMC/Starlight