v1.0.0

NetworkDynamics v1.0.0

Diff since v0.10.17

Breaking

• ModelingToolkit v10 → v11 (#344).
  MTK v11 split into ModelingToolkitBase (MIT) and ModelingToolkit (AGPL);
  NetworkDynamics now only depends on the MIT half, so the AGPL dependency is gone.
  (This does not make the package copyleft-free: the SparseArrays stdlib still pulls in
  SuiteSparse, whose UMFPACK/CHOLMOD/SPQR binaries are GPL-2.0-or-later. That is the
  weaker, non-network-clause copyleft that large parts of the Julia ecosystem already carry.)
  Along with it: SymbolicUtils ≥4, Symbolics ≥7.
• MTK models are no longer simplified by mtkcompile (#344).
  A built-in pipeline (alias/linear-state elimination, algebraic and nonlinear loop
  breaking, simple DAE index reduction) took its place, since mtkcompile lives in the
  AGPL half. Pass mtkcompile=true for the old behavior, mtkcompile=:compare to print
  both side by side, or set the global default with NetworkDynamics.set_mtkcompile!.
  Models containing discrete variables now warn (still unsupported).
• Symbolic expressions as a guess, or bound to an unknown, now error
  (#378)
  (the @variables x(t) = <symbolic expr> [guess=<symbolic expr>] pattern).
  They used to be substituted once, at build time, and frozen into a number — so they silently went stale
  when the values they referenced changed, and an expression that could not be resolved was
  quietly dropped, leaving the variable free. Since formulas are now tracked properly, write
  @variables x(t) [initf = <expr>] (or [guessf = <expr>]) instead; the error message
  names the rewrite. Symbolic values on @parameters do not error: since MTKv11 those create
  a so-called parameter binding, the bound parameter on the lhs is moved to observed thus a
  permanent runtime dependency is injected. This is in contrast to initf, which sets the
  parameter's numeric value once at init time.
• set_mtk_defaults! → set_mtk_defaults, non-mutating
  (#378): rebind the
  result, sys = set_mtk_defaults(sys, ...). A symbolic value now becomes a parameter
  binding (as if written @parameters K = K_e) rather than a default; numeric values
  are unchanged.
• SciMLBase v3 / OrdinaryDiffEq v7
  (#374). Upstream changed
  the default initializealg to check inconsistent initial conditions rather than
  reinitialize them, so ODEProblem(nw, ...) now passes initializealg=BrownFullBasicInit()
  to keep the previous behavior. Override with initializealg=....
  We deliberately chose to deviate from the DiffEq default here because for the kind of systems
  simulated with ND you mostly want DAE reinit at events and sim start.
• VectorContinuousComponentCallback lost affect_neg!
  (#374), matching DiffEq's
  VectorContinuousCallback. The affect now receives an event_signs vector (per output:
  +1 upcrossing, -1 downcrossing, 0 none) and resolves the direction itself.
• find_fixpoint takes an NWState
  (#344). The Vector,
  NWParameter and (NWState, NWParameter) forms are deprecated but still work.

Initialization

• Aliased names are interchangeable
  (#378): it no longer
  matters which of several aliased symbols you attach metadata to. :busbar.u and
  :terminal.u are the same state, so defaults, guesses, bounds and formulas written
  against either are routed to the canonical one.
• Backward-flow initialization
  (#378): an InitFormula
  may now write an observable, "pinning" it as a value downstream formulas read as
  input. This lets you write purely component-local formulas — a parent states what a
  child's output must be, the child's formula inverts its own equation — and have them
  chain end to end, the way power system models are usually initialized. GuessFormula
  pins are hints: they seed the solver but are never consistency-checked, so an entire
  backward chain can be spelled as guesses.
• New initf / guessf metadata
  (#378):
  @variables x(t) [initf = <expr>] declares an initialization equation,
  [guessf = <expr>] a guess. Both also work on @parameters, and there they do something
  a binding cannot: the parameter stays a real, free parameter that the dynamics can use,
  it is merely given its value at initialization. (A binding would eliminate it into an
  observed equation instead.) That is what a setpoint back-computed from the operating point
  needs. A scalar guess=0 and a guessf=<expr> can now coexist on one variable.
  set_initf(sys, target => expr, ...) and set_guessf attach the same thing at system
  level, for targets inside a subsystem (non-mutating, rebind the result).
• More robust on badly scaled models
  (#344,
  #378): a failed init
  solve is retried on a rescaled problem, and the tol/nwtol residual check falls back
  to a Jacobian-scaled residual before giving up. Stiff equations — e.g. a shunt
  capacitor's Dt(V_C) = (ω0/C)·Δi — no longer fail on a roundoff-level mismatch. The
  fallback can only relax the check, never tighten it.
• NWState gains guess, apply_formulas and verbose keywords. With default=true
  values are filled in order: defaults/inits → InitFormulas → guesses (if guess=true)
  → GuessFormulas. find_fixpoint's default start state now uses guess=true.
• initialize_component / initialize_componentwise gain warn=false to silence
  initialization warnings.

Merged pull requests:

• MTK(Base) v11 Compat (#344) (@hexaeder)
• Bump julia-actions/cache to v3, remove cache-save workaround (#346) (@hexaeder)
• fix init macros (#351) (@hexaeder)
• CompatHelper: bump compat for NetworkDynamics to 0.10 for package NetworkDynamicsInspector, (keep existing compat) (#366) (@github-actions[bot])
• Update Buildkite pipeline for the new JuliaGPU cluster (#368) (@maleadt)
• Hw/fix formula handling (#372) (@hexaeder)
• bump sciml versions (#374) (@hexaeder)
• add copy(::Network) and improve metadata dealiasing (#376) (@hexaeder)
• CompatHelper: bump compat for LinearSolve to 5, (keep existing compat) (#377) (@github-actions[bot])
• improve init routine around Formulas (#378) (@hexaeder)
• CompatHelper: bump compat for TimerOutputs to 1, (keep existing compat) (#379) (@github-actions[bot])