Execution Forking

Introduction ​

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Execution Forking (also known as Instancing or Nesting) is a technique used to trigger a single command multiple times within the same tick. This is achieved by leveraging selectors that target multiple entities, effectively "forking" the execution path for each target found.

The Problem: Speed vs. Efficiency ​

Imagine you are creating a bullet system. To ensure the bullet doesn't pass through walls, you need to check for collisions every 1 block. If you move the bullet 1 block per tick, it will appear slow and laggy.

To make it travel 32 blocks instantly while still checking for collisions, you need to run the move-and-check logic 32 times in a single tick. Manually placing 32 command blocks is inefficient and difficult to maintain. Execution Forking solves this by using a single command to generate those 32 instances.

Understanding Instancing ​

In Bedrock Edition, just because you have one command block does not mean it is only running one command. When you use a selector (like @a or @e) that identifies multiple targets, you create a new instance of that command for every entity selected.

Consider this command:

execute at @a run particle minecraft:basic_flame_particle ~ ~ ~

If there are 5 players online, the at @a subcommand forks the execution. Instead of one particle command, it runs 5 separate instances (one at the location of each player).

Multiplicative Execution Forking (MEF) ​

By "nesting" these execution forks, you can exponentially increase the number of times a command runs. This is often called Execute Multipliers or Nesting.

When you stack multiple as or at subcommands, each new fork multiplies the existing ones.

The Math of Nesting ​

The total number of instances created follows a simple power formula:

Instances = n^x

Where n is the number of entities targeted per subcommand, and x is the number of times you nest the execution.

Example: Stacking Branches ​

execute as @e[c=2] as @e[c=2] as @e[c=2] run say hi

In this example, the command will say hi 8 times in a single tick:

1. First Fork: The initial instance targets 2 entities $\to$ 2 instances.
2. Second Fork: Those 2 instances each target 2 more entities $\to$ 4 instances.
3. Third Fork: Those 4 instances each target 2 more entities $\to$ 8 instances.

Execute Visualizer

For convenience, you can use this interactive web-tool developed by @komaramune to visualise MEF and command context trees.

Common Use Cases ​

• Raycasting: Forcing a "bullet" or "laser" to move forward multiple steps in one tick to prevent clipping through walls.
• Mass Entity Updates: Applying complex logic to every entity in a loaded area without using multiple repeating command blocks.
• High-Speed Timers: Running a scoreboard timer multiple times per tick for sub-tick precision.