sem.md

Custom model types

The abstract supertype for all models is AbstractSem. Currently, there are 2 concrete subtypes: Sem{L <: Tuple} and SemFiniteDiff{S <: AbstractSem}. A Sem model holds a tuple of LossTerms (each wrapping an AbstractLoss) and a vector of parameter labels. Both single-group and multigroup models are represented as Sem.

SemFiniteDiff wraps any AbstractSem and substitutes dedicated gradient/hessian evaluation with finite difference approximation:

struct SemFiniteDiff{S <: AbstractSem} <: AbstractSem
    model::S
end

Additionally, you can change how objective/gradient/hessian values are computed by providing methods for evaluate!, e.g. from SemFiniteDiff's implementation:

evaluate!(objective, gradient, hessian, model::SemFiniteDiff, params) = ...

Additionally, we can define constructors like the one in "src/frontend/specification/Sem.jl".