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What's a Jet?

A Jet in Simplicity is a pre-defined, highly optimized function, usually written in C, that can replace a more general (and slower) Simplicity expression.

This process accelerates computation without changing the underlying meaning, which is crucial for blockchain performance.

Think of a Jet as a shortcut:

  • Without Jets: Simplicity executes everything step by step using combinators (correct but slow).

  • With Jets: the same logic runs much faster, but the result is provably identical.

Why are Jets Important?

  • Performance: Blockchain validation must be fast. Jets dramatically reduce computation time.

  • Security: Each Jet is rigorously specified and formally proven to behave exactly like its Simplicity equivalent.

  • Consensus Safety: Jets have fixed, predictable costs to prevent denial-of-service attacks.

  • Scalability: More complex smart contracts become feasible without compromising verification speed.

Jet Creation Process

The development of a Jet follows a rigorous, multi-stage pipeline to ensure its correctness and safety.

1. Prototyping with Simplicity Combinators

The initial phase involves building the desired functionality using only the fundamental building blocks (combinators) of Simplicity.

This serves as a high-level, human-readable blueprint.

2. Formal Specification

The Jet's behavior is described with mathematical precision in Rocq/Coq.

This specification is the “source of truth” against which all implementations (C, Haskell, Rust) are verified.

3. Haskell Implementation

A reference implementation is written in Haskell, a functional programming language.

This version is easier to reason about and serves as an intermediate step before low-level coding.

4. Optimised Native Code Implementation

A highly efficient version of the Jet is coded in C.

This is the implementation that will be executed by the Liquid or Bitcoin client for maximum performance.

5. Benchmarking and Costing for Consensus

The computational resources (CPU time, memory) required by the C implementation are measured precisely.

This data is used to assign a fixed cost/weight to the Jet for consensus rules, preventing denial-of-service attacks.

6. Formal Proof of Equivalence

Using a proof assistant like Coq, a formal, machine-checked proof is constructed.

This proves that the optimized C implementation is semantically identical to the formal specification.

7. Integration and Standardisation

Once fully verified and benchmarked, the Jet is integrated into the core Simplicity library and considered for standardization, making it available for general use in Liquid and Bitcoin scripts.

8. Deployment

Newer Jets are deployed to a Bitcoin testnet for real-world testing.