Adding minor changes that are needed for Enzyme to run, working on understanding why they're needed but for now I just know they are

Author: swilliamson7

src/constants.jl

@@ -26,7 +26,7 @@ function SSPRK3coeff{T}(P::Parameter,Δt_Δ::T) where T
     return SSPRK3coeff{T}(n,s,kn,mn,Δt_Δn,kna,knb,Δt_Δnc)
 end
 
-struct Constants{T<:AbstractFloat,Tprog<:AbstractFloat}
+mutable struct Constants{T<:AbstractFloat,Tprog<:AbstractFloat}
 
     # RUNGE-KUTTA COEFFICIENTS 2nd/3rd/4th order including timestep Δt
     RKaΔt::Array{Tprog,1}

src/default_parameters.jl

@@ -1,4 +1,4 @@
-@with_kw struct Parameter
+@with_kw mutable struct Parameter
 
     T=Float32                 # number format
 
@@ -8,8 +8,8 @@
 
     # DOMAIN RESOLUTION AND RATIO
     nx::Int=100                         # number of grid cells in x-direction
-    Lx::Real=4000e3                     # length of the domain in x-direction [m]
-    L_ratio::Real=2                     # Domain aspect ratio of Lx/Ly
+    Lx::Int=4000e3                      # length of the domain in x-direction [m]
+    L_ratio::Int=2                      # Domain aspect ratio of Lx/Ly
 
     # PHYSICAL CONSTANTS
     g::Real=0.1                         # gravitational acceleration [m/s]
@@ -20,7 +20,7 @@
     R::Real=6.371e6                     # Earth's radius [m]
 
     # SCALE
-    scale::Real=2^6                     # multiplicative scale for the momentum equations u,v
+    scale::Int=2^6                      # multiplicative scale for the momentum equations u,v
     scale_sst::Real=2^15                # multiplicative scale for sst
 
     # WIND FORCING OPTIONS

src/grid.jl

@@ -2,7 +2,7 @@
 
     # Parameters taken from Parameter struct
     nx::Int                             # number of grid cells in x-direction
-    Lx::Real                            # length of the domain in x-direction [m]
+    Lx::Int                             # length of the domain in x-direction [m]
     L_ratio::Real                       # Domain aspect ratio of Lx/Ly
     bc::String                          # boundary condition, "periodic" or "nonperiodic"
     g::Real                             # gravitational acceleration [m/s]
@@ -16,10 +16,10 @@
     ω::Real                             # Earth's angular frequency [s^-1]
     ϕ::Real                             # central latitue of the domain (for coriolis) [°]
     R::Real                             # Earth's radius [m]
-    scale::Real                         # multiplicative scale for momentum equations [1]
+    scale::Int                          # multiplicative scale for momentum equations [1]
 
     # DOMAIN SIZES
-    Δ::Real=Lx / nx                         # grid spacing
+    Δ::T=Lx / nx                            # grid spacing
     ny::Int=Int(round(Lx / L_ratio / Δ))    # number of grid cells in y-direction
     Ly::Real=ny * Δ                         # length of domain in y-direction