Rust-powered system simulation

Drop-in replacement for PathSim. 50-100x faster. Same Python API, powered by a Rust simulation engine with automatic JIT compilation via Cranelift.

GitHub PathSim Docs Consulting Support

Example

Performance

Benchmarks

Cost per integration step across diverse dynamical systems. Lower is better. Each benchmark uses the same model, solver, and tolerances for both engines.

Features

50-100x Faster

Rust core with zero-copy data paths and flat DAG evaluation.

JIT Compiler

Python functions compiled to native machine code via Cranelift.

Drop-in Compatible

Same API as PathSim. Swap the import and go.

21 Solvers

Implicit, explicit, and adaptive integrators for stiff and non-stiff systems.

Event Handling

Zero-crossing detection and scheduled events for hybrid systems.

Extensible

Subclass any block. Custom blocks run at full Rust speed.

Mutable Parameters

Modify block parameters at runtime with automatic reconstruction.

Pyodide Ready

Compiles to WebAssembly for browser-based simulation.

Install

Configure access

Set your access token as an environment variable. Add this to your shell profile (~/.bashrc, ~/.zshrc) to persist it.

export FASTSIM_TOKEN=your_token_here

Install

pip install fastsim \
  --index-url https://__token__:${FASTSIM_TOKEN}@fast.pathsim.org/simple/ \
  --extra-index-url https://pypi.org/simple/

Use