# HodgeMesh Technical Architecture
This document describes the concrete software components and mathematical operators that comprise the **HodgeMesh** (Layer 0) execution engine.
---
## Component Layout
```mermaid
graph TD
classDef component fill:#FFFFFF,stroke:#E5E7EB,stroke-width:2px;
classDef math fill:#EEF2F6,stroke:#4F46E5,stroke-width:2px;
subgraph UserSpace [Simulation & User Interface]
Dashboard[Obs Dashboard HTML/JS]
Sim[Simulation Script]
end
subgraph LedgerSpace [State & Network Layer]
NodeA[HodgeNode A]
NodeB[HodgeNode B]
Server[SSE Telemetry Server]
end
subgraph GeometricSpace [Geometric Foundations]
SSC[SimplicialStateComplex]
Operators[DEC Operators: d0, d1, delta]
Reconciler[Geodesic Reconciler]
Solver[Conjugate Gradient Solver]
end
Sim --> NodeA
Sim --> NodeB
NodeA <-->|Sync Merge| NodeB
NodeA -->|Post Telemetry| Server
Server -->|SSE event-stream| Dashboard
NodeA & NodeB --> SSC
NodeA --> Reconciler
Reconciler --> Operators
Reconciler --> Solver
```
---
## 1. SimplicialStateComplex (`complex.py`)
Tracks causal event histories as a directed simplicial complex:
- **0-simplices (Vertices $V$):** Events. Each vertex tracks its causal parents.
- **1-simplices (Edges $E$):** Directed transitions. If vertex $u$ is a parent of $v$, the edge is $(u, v)$.
- **2-simplices (Triangles $T$):** Formed automatically when a vertex has multiple parents that are themselves causally connected. This preserves the simplicial topology and represents concurrent branches.
---
## 2. DEC Operators (`operators.py`)
Computes the linear operators on $k$-cochains:
- **Exterior Derivative $d_0$ (Gradient):** Maps 0-cochains (vertex potentials) to 1-cochains (edge flows).
- **Exterior Derivative $d_1$ (Curl):** Maps 1-cochains (edge flows) to 2-cochains (triangle circulations).
- **Codifferential $\delta_1$ (Divergence):** Maps 1-cochains to 0-cochains. Implemented as the adjoint $d_0^T$.
- **Laplacian Operators:**
- $L_0 = d_0^T d_0$ (Vertex Laplacian)
- $L_2 = d_1 d_1^T$ (Triangle Laplacian)
---
## 3. Iterative CG Solver (`solver.py`)
A pure-standard-library Conjugate Gradient solver optimized for sparse symmetric positive semi-definite (SPSD) systems.
- Solves $A x = b$ for Laplacians where $A$ has a non-trivial null space.
- Runs to a convergence tolerance of $10^{-6}$ squared residual norm.
---
## 4. Conflict Reconciler (`reconciler.py`)
Performs the Hodge Decomposition.
1. Computes the curl discrepancy vector $b_2 = d_1 \Delta S$.
2. Solves the coexact system $L_2 \beta = b_2$.
3. Computes the coexact conflict flow: $S_{coexact} = d_1^T \beta$.
4. Reconciles the flow: $\Delta S_{reconciled} = \Delta S - S_{coexact}$.
5. Integrates $\Delta S_{reconciled}$ into vertex state potentials using a topological line integral starting from `genesis`.