Merge pull request #2589 from Shreyas-Ekanathan/master

Add FIRK interpolation and addsteps

Author: Oscar Smith

lib/OrdinaryDiffEqFIRK/src/OrdinaryDiffEqFIRK.jl

@@ -26,8 +26,8 @@ using LinearAlgebra: I, UniformScaling, mul!, lu
 import LinearSolve
 import FastBroadcast: @..
 import OrdinaryDiffEqCore
+import OrdinaryDiffEqCore: _ode_interpolant, _ode_interpolant!, has_stiff_interpolation
 import FastPower
-
 using OrdinaryDiffEqDifferentiation: UJacobianWrapper, build_J_W, build_jac_config,
                                      UDerivativeWrapper, calc_J!, dolinsolve, calc_J,
                                      islinearfunction
@@ -45,6 +45,8 @@ include("controllers.jl")
 include("firk_caches.jl")
 include("firk_tableaus.jl")
 include("firk_perform_step.jl")
+include("firk_interpolants.jl")
+include("firk_addsteps.jl")
 include("integrator_interface.jl")
 
 export RadauIIA3, RadauIIA5, RadauIIA9, AdaptiveRadau

lib/OrdinaryDiffEqFIRK/src/alg_utils.jl

@@ -16,3 +16,7 @@ alg_adaptive_order(alg::RadauIIA9) = 5
 
 get_current_alg_order(alg::AdaptiveRadau, cache) = cache.num_stages * 2 - 1
 get_current_adaptive_order(alg::AdaptiveRadau, cache) = cache.num_stages
+
+function has_stiff_interpolation(::Union{RadauIIA3, RadauIIA5, RadauIIA9, AdaptiveRadau})
+    true
+end