Regression with differentiation of expressions involving arrays? #567
Description
PR 530 seems to introduce the intended error message Differentiation of expressions involving arrays and array variables is not yet supported. also in cases which ran fine before the PR.
The following code worked with jac=true before the latest Symbolics.jl release, which incorporated PR #530
using OrdinaryDiffEq, ModelingToolkit
function build_system(n)
@parameters t # or would @variables t be better!?
vars = @variables (Tgas[1:n](t) = fill(100,n)),
(Tsol[1:n](t) = fill(20, n)),
(cR[1:n](t) = fill(3000, n)),
(mflux(t) = 0.5)
@parameters params[1:3]
D = Differential(t)
dp, Tin, h = params
dx = h / n
eqns = Array{Equation}(undef, 3 * n + 1)
count = 1
rR = 5.5e6 .* exp.(.-5680 ./(273 .+ Tsol)) .* (1 .- exp.(.-cR./50))
q = 1e4 * (Tgas - Tsol)
eqns[count] = 0 ~ mflux * 1000 * (Tin - Tgas[1]) - q[1] * dx
count += 1
for i in 2:n
eqns[count] = 0 ~ mflux * 1000 * (Tgas[i-1] - Tgas[i]) - q[i] * dx
count += 1
end
# solids energy balance
for i in 1:n
eqns[count] = D(Tsol[i]) ~ q[i] / (1000 * 2000)
count += 1
end
# gas momentum balance
eqns[count] = 0 ~ - mflux[1] + 5e-3 * sqrt(dp)
count += 1
# reactant concentration equations
for i in 1:n
eqns[count] = D(cR[i]) ~ -rR[i]
count += 1
end
@named sys = ODESystem(eqns, t, vcat(vars...), params)
return sys
end
dp = 100e2
Tin = 200
h = 0.5
parameters = [dp, Tin, h]
N = 100
tspan = (0.0, 1500.0)
sys = build_system(N)
u0 = ones(length(sys.states))
u0[1:N] .= parameters[2]
u0[N+1 : 2*N] .= 20
u0[2*N+1 : 3*N] .= 3000
u0[3*N+1] = 0.5
# works
prob = ODEProblem(sys, u0, tspan, parameters)
# errors with: Differentiation of expressions involving arrays and array variables is not yet supported.
prob = ODEProblem(sys, u0, tspan, parameters, jac=true, sparse=true)
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