fix: allow solving initialization separately

src/systems/problem_utils.jl

@@ -630,13 +630,17 @@ with promoted types.
 
 $(TYPEDFIELDS)
 """
-struct ReconstructInitializeprob{G}
+struct ReconstructInitializeprob{GP, GU}
     """
     A function which when given the original problem and initialization problem, returns
     the parameter object of the initialization problem with values copied from the
     original.
     """
-    getter::G
+    pgetter::GP
+    """
+    Given the original problem, return the `u0` of the initialization problem.
+    """
+    ugetter::GU
 end
 
 """
@@ -674,6 +678,7 @@ with values from `srcsys`.
 function ReconstructInitializeprob(
         srcsys::AbstractSystem, dstsys::AbstractSystem)
     @assert is_initializesystem(dstsys)
+    ugetter = getu(srcsys, unknowns(dstsys))
     if is_split(dstsys)
         # if we call `getu` on this (and it were able to handle empty tuples) we get the
         # fields of `MTKParameters` except caches.
@@ -693,7 +698,7 @@ function ReconstructInitializeprob(
             end
         end
         getters = (tunable_getter, Returns(SizedVector{0, Float64}()), rest_getters...)
-        getter = let getters = getters
+        pgetter = let getters = getters
             function _getter(valp, initprob)
                 oldcache = parameter_values(initprob).caches
                 MTKParameters(getters[1](valp), getters[2](valp), getters[3](valp),
@@ -703,13 +708,13 @@ function ReconstructInitializeprob(
         end
     else
         syms = parameters(dstsys)
-        getter = let inner = concrete_getu(srcsys, syms)
+        pgetter = let inner = concrete_getu(srcsys, syms)
             function _getter2(valp, initprob)
                 inner(valp)
             end
         end
     end
-    return ReconstructInitializeprob(getter)
+    return ReconstructInitializeprob(pgetter, ugetter)
 end
 
 """
@@ -719,7 +724,7 @@ Copy values from `srcvalp` to `dstvalp`. Returns the new `u0` and `p`.
 """
 function (rip::ReconstructInitializeprob)(srcvalp, dstvalp)
     # copy parameters
-    newp = rip.getter(srcvalp, dstvalp)
+    newp = rip.pgetter(srcvalp, dstvalp)
     # no `u0`, so no type-promotion
     if state_values(dstvalp) === nothing
         return nothing, newp
@@ -735,11 +740,10 @@ function (rip::ReconstructInitializeprob)(srcvalp, dstvalp)
     elseif !isempty(newp)
         T = promote_type(eltype(newp), T)
     end
+    u0 = rip.ugetter(srcvalp)
     # and the eltype of the destination u0
-    if T == eltype(state_values(dstvalp))
-        u0 = state_values(dstvalp)
-    elseif T != Union{}
-        u0 = T.(state_values(dstvalp))
+    if T != eltype(u0) && T != Union{}
+        u0 = T.(u0)
     end
     # apply the promotion to tunables portion
     buf, repack, alias = SciMLStructures.canonicalize(SciMLStructures.Tunable(), newp)
@@ -911,11 +915,13 @@ function maybe_build_initialization_problem(
     punknowns = [p
                  for p in all_variable_symbols(initializeprob)
                  if is_parameter(sys, p)]
-    if isempty(punknowns)
+    if initializeprobmap === nothing && isempty(punknowns)
         initializeprobpmap = nothing
     else
-        getpunknowns = getu(initializeprob, punknowns)
-        setpunknowns = setp(sys, punknowns)
+        allsyms = all_symbols(initializeprob)
+        initdvs = filter(x -> any(isequal(x), allsyms), unknowns(sys))
+        getpunknowns = getu(initializeprob, [punknowns; initdvs])
+        setpunknowns = setp(sys, [punknowns; Initial.(initdvs)])
         initializeprobpmap = GetUpdatedMTKParameters(getpunknowns, setpunknowns)
     end
 

test/basic_transformations.jl

@@ -220,7 +220,7 @@ end
     @independent_variables t_units [unit = u"s"]
     D_units = Differential(t_units)
     @variables x(t_units) [unit = u"m"] y(t_units) [unit = u"m"]
-    @parameters g = 9.81 [unit = u"m * s^-2"] # gravitational acceleration
+    @parameters g=9.81 [unit = u"m * s^-2"] # gravitational acceleration
     Mt = ODESystem([D_units(D_units(y)) ~ -g, D_units(D_units(x)) ~ 0], t_units; name = :M) # gives (x, y) as function of t, ...
     Mx = change_independent_variable(Mt, x; add_old_diff = true) # ... but we want y as a function of x
     Mx = structural_simplify(Mx; allow_symbolic = true)

test/initializationsystem.jl

@@ -1194,11 +1194,11 @@ end
     @test integ[x] ≈ 1 / cbrt(3)
     @test integ[y] ≈ 2 / cbrt(3)
     @test integ.ps[p] == 1.0
-    @test integ.ps[q] ≈ 3 / cbrt(3)
+    @test integ.ps[q] ≈ 3 / cbrt(3) atol=1e-5
     prob2 = remake(prob; u0 = [y => 3x], p = [q => 2x])
     integ2 = init(prob2)
-    @test integ2[x] ≈ cbrt(3 / 28)
-    @test integ2[y] ≈ 3cbrt(3 / 28)
+    @test integ2[x] ≈ cbrt(3 / 28) atol=1e-5
+    @test integ2[y] ≈ 3cbrt(3 / 28) atol=1e-5
     @test integ2.ps[p] == 1.0
     @test integ2.ps[q] ≈ 2cbrt(3 / 28)
 end
@@ -1563,3 +1563,38 @@ end
         @test integ[x] ≈ 0.8
     end
 end
+
+@testset "Initialization copies solved `u0` to `p`" begin
+    @parameters σ ρ β A[1:3]
+    @variables x(t) y(t) z(t) w(t) w2(t)
+    eqs = [D(D(x)) ~ σ * (y - x),
+        D(y) ~ x * (ρ - z) - y,
+        D(z) ~ x * y - β * z,
+        w ~ x + y + z + 2 * β,
+        0 ~ x^2 + y^2 - w2^2
+    ]
+
+    @mtkbuild sys = ODESystem(eqs, t)
+
+    u0 = [D(x) => 2.0,
+        x => 1.0,
+        y => 0.0,
+        z => 0.0]
+
+    p = [σ => 28.0,
+        ρ => 10.0,
+        β => 8 / 3]
+
+    tspan = (0.0, 100.0)
+    getter = getsym(sys, Initial.(unknowns(sys)))
+    prob = ODEProblem(sys, u0, tspan, p; guesses = [w2 => 3.0])
+    new_u0, new_p, _ = SciMLBase.get_initial_values(
+        prob, prob, prob.f, SciMLBase.OverrideInit(), Val(true);
+        nlsolve_alg = NewtonRaphson(), abstol = 1e-6, reltol = 1e-3)
+    @test getter(prob) != getter(new_p)
+    @test getter(new_p) == new_u0
+    _prob = remake(prob, u0 = new_u0, p = new_p)
+    sol = solve(_prob; initializealg = CheckInit())
+    @test SciMLBase.successful_retcode(sol)
+    @test sol.u[1] ≈ new_u0
+end