Error related to @autodiff and DiscretizedDynamics()

[jbwillis]

There seems to have been something in a recent package update that is breaking the Quickstart (and my code). I’ve found that my older code works as long as I don’t run Pkg.update() but after I update I get an error. The error seems to be related to the @autodiff stuff when I try to create a discretized model. (also happens when calling Problem() on a continuous model, but this is an mwe).

The following mwe is basically two steps:

1. create a new Julia environment and add RobotDynamics StaticArrays TrajectoryOptimization LinearAlgebra Test
2. Copy + Paste Steps 1 and 2 from http://roboticexplorationlab.org/TrajectoryOptimization.jl/v0.7/quickstart.html#quickstart_page

❯ julia6
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.6.5 (2021-12-19)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

(@v1.6) pkg> activate .
  Activating new environment at `~/scratch/trajopt_quickstart_issue/Project.toml`

(trajopt_quickstart_issue) pkg> add RobotDynamics StaticArrays TrajectoryOptimization LinearAlgebra Test
    Updating registry at `~/.julia/registries/General`
   Resolving package versions...
    Updating `~/scratch/trajopt_quickstart_issue/Project.toml`
  [38ceca67] + RobotDynamics v0.4.6
  [90137ffa] + StaticArrays v1.5.2
  [c79d492b] + TrajectoryOptimization v0.7.0
  [37e2e46d] + LinearAlgebra
  [8dfed614] + Test
    Updating `~/scratch/trajopt_quickstart_issue/Manifest.toml`
  [30b0a656] + ArrayInterfaceCore v0.1.17
  [d360d2e6] + ChainRulesCore v1.15.3
  [9e997f8a] + ChangesOfVariables v0.1.4
  [bbf7d656] + CommonSubexpressions v0.3.0
  [34da2185] + Compat v4.1.0
  [187b0558] + ConstructionBase v1.4.0
  [163ba53b] + DiffResults v1.0.3
  [b552c78f] + DiffRules v1.11.0
  [ffbed154] + DocStringExtensions v0.8.6
  [6a86dc24] + FiniteDiff v2.14.0
  [f6369f11] + ForwardDiff v0.10.30
  [3587e190] + InverseFunctions v0.1.7
  [92d709cd] + IrrationalConstants v0.1.1
  [692b3bcd] + JLLWrappers v1.4.1
  [2ab3a3ac] + LogExpFunctions v0.3.17
  [1914dd2f] + MacroTools v0.5.9
  [77ba4419] + NaNMath v1.0.1
  [21216c6a] + Preferences v1.3.0
  [3cdcf5f2] + RecipesBase v1.2.1
  [ae029012] + Requires v1.3.0
  [38ceca67] + RobotDynamics v0.4.6
  [74be38bb] + RobotZoo v0.3.1
  [6038ab10] + Rotations v1.0.4
  [efcf1570] + Setfield v1.0.0
  [276daf66] + SpecialFunctions v2.1.7
  [90137ffa] + StaticArrays v1.5.2
  [1e83bf80] + StaticArraysCore v1.0.1
  [c79d492b] + TrajectoryOptimization v0.7.0
  [efe28fd5] + OpenSpecFun_jll v0.5.5+0
  [0dad84c5] + ArgTools
  [56f22d72] + Artifacts
  [2a0f44e3] + Base64
  [ade2ca70] + Dates
  [f43a241f] + Downloads
  [9fa8497b] + Future
  [b77e0a4c] + InteractiveUtils
  [b27032c2] + LibCURL
  [76f85450] + LibGit2
  [8f399da3] + Libdl
  [37e2e46d] + LinearAlgebra
  [56ddb016] + Logging
  [d6f4376e] + Markdown
  [ca575930] + NetworkOptions
  [44cfe95a] + Pkg
  [de0858da] + Printf
  [3fa0cd96] + REPL
  [9a3f8284] + Random
  [ea8e919c] + SHA
  [9e88b42a] + Serialization
  [6462fe0b] + Sockets
  [2f01184e] + SparseArrays
  [10745b16] + Statistics
  [4607b0f0] + SuiteSparse
  [fa267f1f] + TOML
  [a4e569a6] + Tar
  [8dfed614] + Test
  [cf7118a7] + UUIDs
  [4ec0a83e] + Unicode
  [e66e0078] + CompilerSupportLibraries_jll
  [deac9b47] + LibCURL_jll
  [29816b5a] + LibSSH2_jll
  [c8ffd9c3] + MbedTLS_jll
  [14a3606d] + MozillaCACerts_jll
  [05823500] + OpenLibm_jll
  [83775a58] + Zlib_jll
  [8e850ede] + nghttp2_jll
  [3f19e933] + p7zip_jll

julia> using TrajectoryOptimization

julia> using RobotDynamics

julia> using StaticArrays

julia> using LinearAlgebra

julia> using RobotDynamics

julia> using Test

julia> const TO = TrajectoryOptimization
TrajectoryOptimization

julia> const RD = RobotDynamics
RobotDynamics

julia> ## Model Definition
       struct DoubleIntegrator{T} <: RD.ContinuousDynamics 
           mass::T
       end

julia> function RD.dynamics(model::DoubleIntegrator, x, u)
           mass = model.mass
           vx,vy = x[3], x[4]
           ax,ay = u[1] / mass, u[2] / mass
           SA[vx, vy, ax, ay]
       end

julia> RD.state_dim(::DoubleIntegrator) = 4

julia> RD.control_dim(::DoubleIntegrator) = 2

julia> model = DoubleIntegrator(1.0)
DoubleIntegrator{Float64}(1.0)

julia> dmodel = RD.DiscretizedDynamics{RD.RK4}(model)
ERROR: MethodError: Cannot `convert` an object of type 
  FiniteDiff.JacobianCache{Vector{Float64}, Vector{Float64}, Vector{Float64}, Vector{Float64}, UnitRange{Int64}, Nothing, Val{:forward}(), Float64} to an object of type 
  FiniteDiff.JacobianCache{Vector{Float64}, Vector{Float64}, Vector{Float64}, UnitRange{Int64}, Nothing, Val{:forward}(), Float64, returntype} where returntype
Closest candidates are:
  convert(::Type{T}, ::T) where T at essentials.jl:205
Stacktrace:
 [1] RobotDynamics.DiscretizedDynamics(continuous_dynamics::DoubleIntegrator{Float64}, integrator::RobotDynamics.RK4)
   @ RobotDynamics ~/.julia/packages/RobotDynamics/xW4Xp/src/discretized_dynamics.jl:763
 [2] (RobotDynamics.DiscretizedDynamics{RobotDynamics.RK4, Q, JCH} where {Q, JCH})(continuous_dynamics::DoubleIntegrator{Float64})
   @ RobotDynamics ~/.julia/packages/RobotDynamics/xW4Xp/src/discretized_dynamics.jl:183
 [3] top-level scope
   @ REPL[16]:1

[jbwillis]

Did more digging, this seems to be due to a change in FiniteDiff.jl. I don't get this error with version v2.11.0 but I do get the error with v2.14.0.

[bjack205]

Fixed by this PR in RobotDynamics.

Works with the latest version of RobotDynamics (v0.4.7).

[SkylerHawkins]

Hello, I'm just now getting into this library and I'm having this same issue when trying to run the examples such as Cartpole and Quadrotor. I think the compats may be outdated, can anyone give me their compats so I can replicate without running into this FiniteDiff error?