Help to create a structure to use ForwardDiff package

General Usage
1

Hi!

I want to use the ForwardDiff package to perform automatic differentiation of a function. However, this function requires an structure in which I am declaring like this:

@with_kw mutable struct MyStruct{T<:Real}
    a::T = 0
    b::T = 0
    c::T = 0
end

However, this is leading to problems related to ForwardDiff due to the types. The solution seems to declare something like:

@with_kw mutable struct MyStruct{T1,T2,T3}
    a::T1 = 0
    b::T2 = 0
    c::T3 = 0
end

However, I have more than 30 variables. Is there a way to make this cleaner instead of writing {T1,T2,T3,T4,...,T30}?

2

One option is to construct (and deconstruct) a vector with those numbers, and call that from ForwardDiff. but they are all of different types? Maybe parametrizing with one type can help

1 Like
3

I do not think this will help. The structure is something that is used inside a complicated algorithm. Those are not the values I want to differentiate. The problem is that, when the structure is allocated, some are dual numbers and some are not.

4

Either you can promote them to the same type, or introduce more granular type parameters.

Hard to say more without an MWE.

5

@qstruct_fp in https://github.com/cstjean/QuickTypes.jl is useful for this

6

It is very difficult to provide a MWE because it is the SGP4 propagator. The code is big, and I am not sure where the error is created. I only know that using a different type for each variable solves the problem.

Thanks! This should help me :slight_smile: