Vector-Jacobian Product Operators

VecJacOperator{T}(f,u::AbstractArray,p=nothing,t::Union{Nothing,Number}=nothing;autodiff=true,ishermitian=false,opnorm=true)

The VecJacOperator is a linear operator J'*v where J acts like df/du for some function f(u,p,t). For in-place operations mul!(w,J,v), f is an in-place function f(du,u,p,t).