GitHub

Context Internals

The runtime data stack is:

  1. ProcessContext
  2. SubContext
  3. SubContextView

1. ProcessContext

ProcessContext{D,Reg} holds (src/Context/StructDefs.jl):

  • subcontexts::D: named tuple of subcontexts plus globals.
  • registry::Reg: a NameSpaceRegistry used for static routing and lookup.

Access patterns (src/Context/ProcessContexts.jl):

  • pc[:name] or pc.name by subcontext symbol.
  • pc[obj] by algorithm/state value/type (resolved through registry key).

globals is a regular field in subcontexts; runtime code injects process-level values there (like process, lifetime, algo).

2. SubContext

SubContext{Name,Data} stores (src/Context/StructDefs.jl):

  • data::NamedTuple: local variables owned by that entity.

Initialization builds empty SubContexts for every registry key, then fills them by init.

Route/share metadata is deliberately not stored on SubContext. Plan routing is resolved into step-local StepRouting values and attached to SubContextView types while a child runs. This keeps persistent context shape independent from execution-plan wiring.

3. SubContextView

step!, init, and cleanup run against a SubContextView (src/Context/View/StructDef.jl).

A view carries:

  • the full context,
  • the current identifiable instance,
  • optionally injected locals.
  • route/share metadata for the current step, as type parameters.

Property access is generated through VarLocations (src/Context/View/Locations.jl):

  • local vars,
  • shared-context vars from the current step routing,
  • routed vars from the current step routing,
  • injected vars.

Name precedence for reads is determined by NamedTuple merge order. Later groups override earlier groups:

  1. injected vars
  2. local vars
  3. routed vars
  4. shared vars

This means local and injected names override route/share names on collisions.

4. Merging and Replacing

merge(view, namedtuple) (src/GeneratedCode/SubContextView.jl) maps return names back to concrete target subcontexts and variables.

  • Existing mapped variable: update that mapped target.
  • Unknown variable: added to the current local subcontext.

replace(view, (;SubKey => nt)) replaces the full subcontext and is used during init.

merge_into_subcontexts (src/Context/ProcessContexts.jl) enforces that subcontext structure remains valid.

A type-change guard in generated merge asserts the new ProcessContext type stays identical, preventing accidental type instability.