SII indexing for ComponentArray ODE solutions (sol[:x], sol(t; idxs=:x)) - #396
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ChrisRackauckas merged 3 commits intoJul 24, 2026
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When an AbstractODEProblem has ComponentArray u0 and no symbolic sys is set on the ODEFunction, expose top-level component keys (and parameter keys when p is also a ComponentArray) through SII. This makes sol[:x], sol(t; idxs=:x), sol(t; idxs=[:x,:y]), and sol.ps[:a] work without a manual SymbolCache, matching the interface discussed on SciML/DifferentialEquations.jl#957. Existing getsyms plotting labels are unchanged. Explicit sys on the ODEFunction is still preferred when present. Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
New #957 indexing tests `using SymbolicIndexingInterface`; it must be a direct Downstream dep (not only transitive via SciMLBase). Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
ChrisRackauckas
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July 24, 2026 06:17
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Summary
Implements SymbolicIndexingInterface support for ODE problems whose state is a
ComponentArray, so named solution indexing works without a hand-builtSymbolCache.Fixes the ergonomics request in SciML/DifferentialEquations.jl#957 (and follows the design note there from @AayushSabharwal / @ChrisRackauckas: SII overloads rather than
getpropertyforwarding onDiffEqArray).Behavior
When
u0 isa ComponentArrayand theODEFunctionhas no symbolicsys:sol[:x],sol(t; idxs=:x),sol(t; idxs=[:x, :y])use top-level component keysp isa ComponentArray,sol.ps[:a]works the same wayu.b = (x,y)) remain indexable assol[:b](returns the sub-component)When
sysis already set on the function (MTK / manualSymbolCache), that system is left alone.Implementation
ext/ComponentArraysSciMLBaseExt.jlwith a smallComponentArrayIndexProviderandsymbolic_container(::AbstractODEProblem{<:ComponentArray})getsymsplotting labelsTests
sysNotes
This PR should be ignored until reviewed by @ChrisRackauckas.
Limitations / follow-ups
AbstractODEProblemfor now (SDE/DDE/etc. can reuse the same provider later)Symbol("b.x")are not registered as separate variables (top-level keys only)save_idxsComponentArray behavior (already worked for single labels)