Linearize is failing when using AutoFiniteDiff()

[1-Bart-1]

This MWE fails:

using ModelPredictiveControl, FiniteDiff, DifferentiationInterface

ad_type = AutoFiniteDiff()

function f(x, u, _ , p)
    g, L, K, m = p          # [m/s²], [m], [kg/s], [kg]
    θ, ω = x[1], x[2]       # [rad], [rad/s]
    τ  = u[1]               # [Nm]
    dθ = ω
    dω = -g/L*sin(θ) - K/m*ω + τ/m/L^2
    return [dθ, dω]
end
h(x, _ , _ ) = [180/π*x[1]] # [°]
p_model = [9.8, 0.4, 1.2, 0.3]
nu, nx, ny, Ts = 1, 2, 1, 0.1
vu, vx, vy = ["\$τ\$ (Nm)"], ["\$θ\$ (rad)", "\$ω\$ (rad/s)"], ["\$θ\$ (°)"]
model = setname!(NonLinModel(f, h, Ts, nu, nx, ny; p=p_model, jacobian=ad_type); u=vu, x=vx, y=vy)

linmodel = ModelPredictiveControl.linearize(model, x=[π, 0], u=[0])

While it runs succesfully when using ad_type = AutoForwardDiff()

Stacktrace:

ERROR: LoadError: ArgumentError: range must be non-empty
Stacktrace:
  [1] maximum
    @ ./range.jl:851 [inlined]
  [2] finite_difference_jacobian!(J::Matrix{…}, f::DifferentiationInterface.FixTail{…}, x::Vector{…}, cache::FiniteDiff.JacobianCache{…}, f_in::Nothing; relstep::Float64, absstep::Float64, colorvec::UnitRange{…}, sparsity::Nothing, dir::Bool)
    @ FiniteDiff ~/.julia/packages/FiniteDiff/EBPBu/src/jacobians.jl:450
  [3] finite_difference_jacobian! (repeats 2 times)
    @ ~/.julia/packages/FiniteDiff/EBPBu/src/jacobians.jl:406 [inlined]
  [4] jacobian!
    @ ~/.julia/packages/DifferentiationInterface/7eD1K/ext/DifferentiationInterfaceFiniteDiffExt/twoarg.jl:391 [inlined]
  [5] linfunc!
    @ ~/.julia/packages/ModelPredictiveControl/NFmDi/src/model/linearization.jl:42 [inlined]
  [6] linearize_core!
    @ ~/.julia/packages/ModelPredictiveControl/NFmDi/src/model/linearization.jl:195 [inlined]
  [7] linearize!(linmodel::LinModel{…}, model::NonLinModel{…}; x::Vector{…}, u::Vector{…}, d::Vector{…})
    @ ModelPredictiveControl ~/.julia/packages/ModelPredictiveControl/NFmDi/src/model/linearization.jl:166
  [8] linearize!
    @ ~/.julia/packages/ModelPredictiveControl/NFmDi/src/model/linearization.jl:155 [inlined]
  [9] linearize(model::NonLinModel{…}; kwargs::@Kwargs{…})
    @ ModelPredictiveControl ~/.julia/packages/ModelPredictiveControl/NFmDi/src/model/linearization.jl:131
 [10] top-level scope
    @ ~/Code/KitePredictiveControl.jl/mwe/finitediff.jl:37
 [11] include(fname::String)
    @ Main ./sysimg.jl:38
 [12] top-level scope
    @ REPL[1]:1
in expression starting at /home/bart/Code/KitePredictiveControl.jl/mwe/finitediff.jl:37
Some type information was truncated. Use `show(err)` to see complete types.

[franckgaga]

Thanks for the report! I can reproduce, will investigate on this.

[franckgaga]

Should be solved by #186. I will release an update just after merging the changes.