Explosion Parallelization

Say goodbye to explosion lag on your server.

Explosion Parallelization rewires Minecraft's explosion engine to run on multiple CPU cores simultaneously. Where vanilla processes every explosion ray and entity damage one-by-one on the main thread, this mod divides the work across your server's available cores, cutting explosion overhead by 60-70%.

The Problem

Vanilla explosions are entirely single-threaded. A single TNT detonation traces 1,352 rays through the world, each checking up to 30 blocks for blast resistance — that's ~40,000 block lookups. Now multiply that by a 5×5×5 TNT cube (125 TNT blocks detonating simultaneously), and the main thread simply can't keep up. Result: your server's TPS tanks, and everyone lags.

The Solution

Explosion Parallelization splits the explosion pipeline into two parallel phases on a ForkJoinPool-backed thread pool:

Phase	Work	Parallelization
Ray Tracing	1,352 rays × ~30 steps each	Split evenly across worker threads; results collected into a dense boolean grid — lock-free, no merge overhead
Entity Damage	Exposure checks, damage calculation, knockback vectors	Workers compute read-only; main thread applies results

All else — block drops, fire placement — stays on the main thread, with proper synchronization to prevent world corruption. Chunk access from worker threads bypasses the main-thread dispatch queue via ChunkSafeAccessor, avoiding deadlocks.

Performance

Benchmarked with a 5×5×5 TNT cube detonation (spark profiler, 1-minute recording):

Setup	MSPT (95th %ile)
Vanilla	~277
This mod	~74.5
Lithium alone	~130
This mod + Lithium	~37.8

Recommendation: Use together with Lithium — this mod parallelizes explosion calculation, Lithium optimizes entity collision checks; they complement each other perfectly.

Features

• Vanilla-identical by default — With all settings at their defaults, explosion behavior matches vanilla exactly
• Adaptive Ray Grid — Reduce explosion rays from 1,352 down to as few as 296 for faster processing (adaptiveRays)
• Adjustable Entity Sampling — Tune entity visibility sampling density: Accurate (vanilla ~45 samples/entity), Fast (~24), Aggressive (~12)
• Ray Lookup Acceleration — Pre-computed O(1) direction→distance lookup table, trading minor angular accuracy for massive speedup in entity exposure checks
• Precise Ray Toggle — Choose between vanilla float-accumulation ray stepping (accurate) or precomputed integer-delta stepping (faster, tiny deviation)
• Live Toggle — Enable, disable, or reconfigure on the fly with in-game commands — no restart needed
• Thread-safe by design — Deterministic results: all random factors are pre-generated on the main thread so explosion patterns remain consistent

Commands

(Requires OP level 2 / Gamemaster)

/parallel explosion                           Show current status
/parallel explosion true|false                Toggle parallel explosions
/parallel explosion sampling accurate|fast|aggressive   Set entity sampling quality
/parallel explosion raylookup true|false       Toggle ray lookup acceleration
/parallel explosion adaptiveRays <0..16>       Set adaptive ray grid size
/parallel explosion preciseRays true|false     Toggle precise ray tracing
/parallel explosion reload                    Reload config from file

Configuration

All settings are stored in config/explosion-parallelization.json and can be changed in-game or by editing the file directly:

Setting	Default	Description
enabled	true	Master switch
samplingFactor	2.0	Entity visibility sampling density (2.0=accurate, 1.0=fast, 0.5=aggressive)
rayLookup	false	Enable fast O(1) ray distance lookup table
adaptiveRays	0	Ray grid coarseness (0=vanilla 1352 rays, 8=fast ~296 rays)
preciseRays	true	Use vanilla float-accumulation ray stepping; disable for faster integer-delta paths

Behavior-Changing Options

Default config preserves vanilla behavior exactly. The following options intentionally deviate:

samplingFactor < 2.0

Reduces the number of ray samples per entity for getSeenPercent. Fewer samples = less accurate knockback in edge cases, but significantly faster.

rayLookup = true

Replaces per-sample DDA traversal with a pre-computed direction→distance lookup from the explosion's 1,352 rays. ~5.5° angular resolution means partially-occluded entities at long range may see up to 10-15% deviation.

adaptiveRays > 0

Reduces explosion ray grid resolution. Fewer rays = coarser explosion shape but better performance.

preciseRays = false

Switches from float-accumulation ray stepping (vanilla) to precomputed integer-delta paths. Slightly different block traversal near block corners; imperceptible in most scenarios. Best paired with other acceleration options for maximum throughput.

Dependencies

• Fabric API
• parallel-core

Server-side only — clients do not need to install this mod.