Compatibility with Tracker from Flux for AD? #570
Comments
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I can take a closer look at this after Wednesday. |
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OK, so this appears to be because: julia> Tracker.track(identity, rand(3)) |> typeof |> supertype
AbstractArray{Float64,1}while julia> Tracker.track(identity, rand(3)) |> eltype
Tracker.TrackedReal{Float64}So in a sense, I also see that Tracker.jl is on its way out. I'm not familiar with Flux's status quo; do you know why they're replacing Tracker.jl and what they're replacing it with? |
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After #571, I think the next issue is with using Tracker
using StaticArrays
x = Tracker.track(identity, 1.0)
y = [Tracker.track(identity, 2.0), Tracker.track(identity, 2.0)]
@show typeof(x * y)which results in TrackedArray{…,Array{Tracker.TrackedReal{Float64},1}}i.e., a But Tracker is being replaced with Zygote of course. It might make sense to switch to try the |
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Also wanted to point to https://github.com/tkoolen/RigidBodyDynamicsDiff.jl, which, though experimental, has moderately optimized gradients w.r.t. |
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Thank you for your detailed reply! using RigidBodyDynamics
using RigidBodySim
using DifferentialEquations
using Zygote
urdf = joinpath(dirname(pathof(RigidBodySim)), "..", "test", "urdf", "Acrobot.urdf")
mechanism = parse_urdf(Float32, urdf)
remove_fixed_tree_joints!(mechanism);
state = MechanismState(mechanism)
shoulder, elbow = joints(mechanism)
# Set the initial state
configuration(state, shoulder) .= 0.3
configuration(state, elbow) .= 0.4
velocity(state, shoulder) .= 1.
velocity(state, elbow) .= 2.;
mutable struct ControllerParams
param::Float32
end
p_test = ControllerParams(5)
function create_controller(p::ControllerParams)
function control!(τ, t, state)
view(τ, velocity_range(state, shoulder)) .= p.param * sin(t)
view(τ, velocity_range(state, elbow)) .= -configuration(state, shoulder)
end
return control!
end
function simulate_full(p::ControllerParams)
cc! = create_controller(p)
open_loop_dynamics = Dynamics(mechanism, cc!);
problem = ODEProblem(open_loop_dynamics, state, (0., 1))
sol = solve(problem, Tsit5(), abs_tol = 1e-7, dt = 0.05)
println("Done")
return sol[end][1]
end
# Check if we can get the gradient of a function using a ControllerParams
@show gradient(p -> p.param * 2, p_test)
# Check if we can simulate 1 sec of Dynamics
@show simulate_full(p_test)
# Check if we can get the gradient of the Dynamic with the respect of a ControllerParams
# -> Breaks
@show gradient(simulate_full, p_test)Stack trace: What I am trying to do is basically learn a parameterized controller with gradient descent. |
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I actually thought it was a bug with Atom and I tried to execute the above script using the CLI but it's the same error |
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(away from a computer) I actually think that particular error is just due to the |
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I actually removed the println and got the exact same error. |
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Is it correct that Zygote and RigidBodyDynamics are not yet compatible? In my simple test, I fail because Zygote does not yet support mutating arrays. |
Hey there,
I am trying to use Flux models as torque controllers and eventually backpropagate from some sort of loss to the parameters of those models but it seems that RigidBodyDynamics.jl breaks Tracker.
I know that Flux and Tracker work with DifferentialEquations.jl (DiffEqFlux.jl as an example).
Edit: The reason why I am using
Tracker.TrackedReal{Float64}as the type for MechanismState is because I need those parameters to record the operations being executed on them (just like the ForwardDiff.jl tutorial for this package)Here is a minimal repro:
Stack trace:
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