logabsdetjac with Stacked throws: "ArgumentError: reducing over an empty collection is not allowed"

[turinglang]

logabsdetjac with Stacked throws: "ArgumentError: reducing over an empty collection is not allowed"

[torfjelde]

Ah, nice catch; thanks!

Alternatively, we can add the following method

function logabsdetjac(b::Stacked{<:Any, 1}, x::AbstractVector{<:Real})
    return sum(logabsdetjac(b.bs[1], x[b.ranges[1]]))
end

[vandenman]

That's probably a cleaner solution. Shall I open a PR adding that method?

[torfjelde]

That would be great!:)

Also, maybe just add

# Ensure `Stacked` works for a single bijector
d = (MvNormal(2, 1.0),)
sb = Stacked(bijector.(d), [1:2])
x = [.5, 1.]
@test sb(x) == x
@test logabsdetjac(sb, x) == 0
@test forward(sb, x) == (rv = x, logabsdetjac = zero(eltype(x)))

after

Bijectors.jl/test/interface.jl

Line 710 in dfca913

@test log(abs(det(ForwardDiff.jacobian(isb, y)))) ≈ logabsdetjac(isb, y)

so we also have some tests for this.