Architecture¶

FoamNordic separates workload declaration from repeated solver execution. Python compiles an immutable plan and prepares an isolated case; native components own field access, numerical execution, model evaluation, transport and atomic publication.

flowchart LR
    API[Python API] --> LS[Longship]
    LS --> OF[OpenFOAM adapter]
    LS --> MH[ModelHost]
    OF <-->|Fjord| MH
    OF --> SF[Solver fields and equations]
    MH --> BN[BindNordic]
    BN --> FNOM[FNOM model or table]

OpenFOAM retains equations, correction order, mesh, and boundary conditions. FoamNordic evaluates declared operators at adapter-owned boundaries.

Component boundaries¶

Component	Responsibility	Does not own
Python API	Workload, field, model, placement and scheduler declarations	Repeated solver execution
Longship	Plan compilation, placement, readiness, lifecycle, logs and durable results	Physical equations
OpenFOAM adapter	Current field views, equation hooks, topology generation and atomic commit	Model implementation
Fjord	Bounded numeric transport and exchange identity	Persistent model or field state
Rune	Binary frame representation	Channel selection or solver semantics
Harbor	Atomic request and response sequencing	Numerical interpretation
ModelHost	Resident process, admission, workspace and backend invocation	Solver progression
Smedja	Reusable packing and execution workspace	Cross-request physical state
BindNordic	FNOM, tensor contracts, scalers and backend execution	Simulation semantics
External solver adapter	Call sites, equations, correction order and physical meaning	Generic model runtime

Deployment forms¶

Form	Process layout	Normal data path
Solver-native function	Symbolic graph inside the OpenFOAM adapter	No ModelHost or inter-process exchange
Local resident model	OpenFOAM and one ModelHost on the local host	Shared memory with Unix-socket control
Slurm attached model	One ModelHost beside solver ranks on each allocated node	Node-local shared memory

Local and Slurm execution consume the same compiled plan. FNOM is the deployment boundary for model tensors, scaling, backend metadata and payloads; placement changes do not alter the field contract.

Architecture reference¶

Document	Contract
Design principles	Ownership, failure, reproducibility, and non-goals
OpenFOAM integration	Fields, topology, closures, numerics, and external adapters
Native runtime	Admission, workspaces, backend capabilities, and atomic output
Native transport	Rune frames, Harbor exchanges, channels, and memory credit
FNOM	Artefact contents, backend selection, validation, and trust
Execution lifecycle	Local and Slurm launch, ownership, shutdown, and generations
Observations	Read-only monitoring, retention, and backpressure
Package boundary	Model execution and simulation semantics