Matrix-Free Linear Operators and Specializations on Linearity

SciML has the SciMLOpereators.jl library for defining linear operators. The ODE solvers will specialize on this property, for example using the lienar operators automatically with Newton-Krylov methods for matrix-free Newton-Krylov optimzations, but also allows for methods that requires knowing that part of the equation is linear, like exponential integrators. See the SciMLOperators.jl library for more information.