2.3 KiB
2.3 KiB
ADR-0007: Runtime API and Simulation Engine Boundaries
Status
Accepted
Context
The simulator consists of multiple layers with distinct responsibilities:
- a host-facing API layer used by benchmarks and user code,
- a discrete-event simulation engine that executes requests,
- device components that model hardware behavior.
Without strict boundaries, orchestration logic can leak into components, or simulation internals can become entangled with user-facing APIs.
This ADR defines clear responsibility boundaries between:
- runtime API,
- simulation engine (sim_engine),
- hardware components.
Decision
D1. Runtime API is host-facing orchestration only
The runtime API represents host/driver-level behavior and MUST:
- expose high-level operations (tensor deployment, kernel launch),
- submit requests only to endpoint components (e.g., IO_CPU),
- await completion via futures/handles,
- own and persist host-side metadata (tensor allocation maps, kernel bindings).
The runtime API MUST NOT:
- hardcode hop-by-hop routing or fan-out,
- directly invoke internal components (M_CPU, PE_CPU, engines),
- embed topology- or routing-specific assumptions.
D2. Simulation engine executes and schedules requests
The simulation engine (sim_engine) MUST:
- inject requests into the compiled topology graph,
- schedule and execute events using a discrete-event model,
- manage correlation ids and completion tracking,
- decompose operations into low-level requests when required (e.g., MemoryWrite events).
The simulation engine MUST NOT:
- define tensor semantics,
- define kernel execution policies,
- expose internal graph details to the runtime API.
D3. Components own fan-out and aggregation
Device-side components MUST:
- fan-out requests to downstream domains (IO_CPU → M_CPU → PE_CPU → schedulers/engines),
- aggregate completion and failure signals,
- propagate results deterministically upstream.
Neither the runtime API nor the simulation engine may orchestrate component-level fan-out explicitly.
Consequences
- Runtime APIs remain stable as topology and routing evolve.
- Simulation internals can change without affecting user-facing code.
- Component implementations remain swappable via DI.
Links
- SPEC R4, R7, R8
- ADR-0008 (Tensor deployment)
- ADR-0009 (Kernel execution)