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