> For the complete documentation index, see [llms.txt](https://threadforge.gitbook.io/threadlink-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://threadforge.gitbook.io/threadlink-documentation/engineer-reference/deterministic.md).

# Deterministic Toolkit

Everything a simulation needs to give the same result on every machine, runtime and compiler: numbers, vectors and rotations in fixed point, and the framework's one source of randomness. Networked simulation, lockstep, replays and procedural generation build on it.

The toolkit lives in the `Threadlink.Deterministic` assembly (namespace `Threadlink.Deterministic`), which references no engine type, so a deterministic simulation assembly can depend on it without depending on Unity. Its only Threadlink dependencies are `Threadlink.Shared` (hashing) and `Threadlink.Generated` (RNG domains).

| Page                                                                                        | Covers                                                                                  |
| ------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------- |
| [Fixed Point](/threadlink-documentation/engineer-reference/deterministic/fixed-point.md)    | `FP`, `FPVector2`, `FPVector3`, `FPQuaternion`, and conversion to and from Unity types. |
| [StatelessRNG](/threadlink-documentation/engineer-reference/deterministic/stateless-rng.md) | Streams, sources, identity, samplers, domains.                                          |

`Bits` provides bit counts and rotations of 64-bit words that are the same on every runtime (Mono, IL2CPP and CoreCLR): `TrailingZeroCount`, `LeadingZeroCount`, `PopCount` and `RotateLeft`.

State that is copied, hashed and saved as raw bytes, such as a simulation's frames, is the domain of the [Memory](/threadlink-documentation/engineer-reference/memory.md) toolkit.