Automatic differentiation with subset of parameters in ModelingToolkit

[ChrisRackauckas]

@Antomek

But this would not work with Zygote, as mutation is not supported.

Instead just build the array instead of mutating, using a comprehension with an ifelse statement.

new_p = [ifelse(i in p_subset_indices,p_subset[i],p) for i in 1:length(p)]

Or use a Zygote.Buffer.