`MultiThreadEnv` with custom (continuous) action spaces fails

[rejuvyesh]

I am trying to integrate RL.jl with Dojo.jl in dojo-sim/Dojo.jl#9. However current MultiThreadEnv wrapper fails to work with the BoxSpace defined there, even though we have Base.in, Base.length and Random.rand are defined. Issue seems to be in the use of selectdim in the current implementation.

Wrapper states are a Vector of Vector

N_ENV = 2
env_vec = [Dojo.DojoRLEnv("cartpole") for i in 1:N_ENV]
env = MultiThreadEnv(env_vec)
env.states

results in:

julia> env.states
2-element Vector{Vector{Float64}}:
 [0.8223080697554248, 1.6284598982949312, 0.464146354303141, -0.2796568159199919]
 [0.0, 0.0, 3.141592653589793, 0.0]

However selectdim(env.states, 1, 1) gives a 0-dim view:

julia> selectdim(env.states, 1, 1)
0-dimensional view(::Vector{Vector{Float64}}, 1) with eltype Vector{Float64}:
[0.8223080697554248, 1.6284598982949312, 0.464146354303141, -0.2796568159199919]

which cannot take the vector observations as currently implemented:

julia> selectdim(env.states, 1, 1) .= randn(4)
ERROR: DimensionMismatch("cannot broadcast array to have fewer non-singleton dimensions")
Stacktrace:
 [1] check_broadcast_shape
   @ ./broadcast.jl:535 [inlined]
 [2] check_broadcast_axes
   @ ./broadcast.jl:543 [inlined]
 [3] instantiate
   @ ./broadcast.jl:284 [inlined]
 [4] materialize!
   @ ./broadcast.jl:871 [inlined]
 [5] materialize!(dest::SubArray{Vector{Float64}, 0, Vector{Vector{Float64}}, Tuple{Int64}, true}, bc::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1}, Nothing, typeof(identity), Tuple{Vector{Float64}}})
   @ Base.Broadcast ./broadcast.jl:868
 [6] top-level scope
   @ REPL[28]:1
 [7] top-level scope
   @ ~/.julia/packages/CUDA/Axzxe/src/initialization.jl:52

[findmyway]

I guess the problem comes from the BoxSpace defined in your PR. When initializing the MultiThreadEnv, only Space defined in RLBase is recognized at the moment. Let me experiment with your PR first and see how to address it.

[findmyway]

Should be fixed with rejuvyesh/Dojo.jl#1

Closing this issue for now. I'll add more suggestions in your PR there. But I think we really should work on #268 at some time.