const and immutable structs, non-breaking

src/callbacks_stage/entropy_bounded_limiter.jl

@@ -5,7 +5,7 @@
 @muladd begin
 #! format: noindent
 
-mutable struct EntropyBoundedLimiter{RealT <: Real}
+struct EntropyBoundedLimiter{RealT <: Real}
     exp_entropy_decrease_max::RealT # < 0
 end
 

src/callbacks_step/alive.jl

@@ -15,8 +15,8 @@ time steps. If `analysis_interval ≂̸ 0`, the output is omitted every
 """
 mutable struct AliveCallback
     start_time::Float64
-    alive_interval::Int
-    analysis_interval::Int
+    const alive_interval::Int
+    const analysis_interval::Int
 end
 
 function AliveCallback(; analysis_interval = 0,

src/callbacks_step/analysis.jl

@@ -49,15 +49,15 @@ mutable struct AnalysisCallback{Analyzer, AnalysisIntegrals, InitialStateIntegra
     start_time_last_analysis::Float64
     ncalls_rhs_last_analysis::Int
     start_gc_time::Float64
-    interval::Int
-    save_analysis::Bool
-    output_directory::String
-    analysis_filename::String
-    analyzer::Analyzer
-    analysis_errors::Vector{Symbol}
-    analysis_integrals::AnalysisIntegrals
+    const interval::Int
+    const save_analysis::Bool
+    const output_directory::String
+    const analysis_filename::String
+    const analyzer::Analyzer
+    const analysis_errors::Vector{Symbol}
+    const analysis_integrals::AnalysisIntegrals
     initial_state_integrals::InitialStateIntegrals
-    cache::Cache
+    const cache::Cache
 end
 
 # TODO: Taal bikeshedding, implement a method with less information and the signature

src/callbacks_step/save_restart.jl

@@ -12,7 +12,7 @@
 
 Save the current numerical solution in a restart file every `interval` time steps.
 """
-mutable struct SaveRestartCallback
+struct SaveRestartCallback
     interval::Int
     save_final_restart::Bool
     output_directory::String

src/callbacks_step/steady_state.jl

@@ -11,7 +11,7 @@
 Terminates the integration when the [`residual_steady_state(du, equations)`](@ref)
 falls below the threshold specified by `abstol, reltol`.
 """
-mutable struct SteadyStateCallback{RealT <: Real}
+struct SteadyStateCallback{RealT <: Real}
     abstol::RealT
     reltol::RealT
 end

src/callbacks_step/stepsize.jl

@@ -27,7 +27,7 @@ diffusive CFL number, or a function of time `t` returning a `Real` number.
 By default, the timestep will be adjusted at every step.
 For different values of `interval`, the timestep will be adjusted every `interval` steps.
 """
-mutable struct StepsizeCallback{CflAdvectiveType, CflDiffusiveType}
+struct StepsizeCallback{CflAdvectiveType, CflDiffusiveType}
     cfl_advective::CflAdvectiveType
     cfl_diffusive::CflDiffusiveType
     interval::Int

src/callbacks_step/time_series.jl

@@ -27,12 +27,12 @@ Currently this callback is only implemented for [`TreeMesh`](@ref) and [`Unstruc
 """
 mutable struct TimeSeriesCallback{RealT <: Real, uEltype <: Real, SolutionVariables,
                                   VariableNames, Cache}
-    interval::Int
-    solution_variables::SolutionVariables
-    variable_names::VariableNames
-    output_directory::String
-    filename::String
-    point_coordinates::Array{RealT, 2}
+    const interval::Int
+    const solution_variables::SolutionVariables
+    const variable_names::VariableNames
+    const output_directory::String
+    const filename::String
+    const point_coordinates::Array{RealT, 2}
     # Point data is stored as a vector of vectors of the solution data type:
     # * the "outer" `Vector` contains one vector for each point at which a time_series is recorded
     # * the "inner" `Vector` contains the actual time series for a single point,
@@ -42,7 +42,7 @@ mutable struct TimeSeriesCallback{RealT <: Real, uEltype <: Real, SolutionVariab
     point_data::Vector{Vector{uEltype}}
     time::Vector{RealT}
     step::Vector{Int}
-    time_series_cache::Cache
+    const time_series_cache::Cache
 end
 
 function Base.show(io::IO, cb::DiscreteCallback{<:Any, <:TimeSeriesCallback})

src/callbacks_step/visualization.jl

@@ -5,8 +5,8 @@
 @muladd begin
 #! format: noindent
 
-mutable struct VisualizationCallback{PlotDataCreator, SolutionVariables, VariableNames,
-                                     PlotCreator}
+struct VisualizationCallback{PlotDataCreator, SolutionVariables, VariableNames,
+                             PlotCreator}
     plot_data_creator::PlotDataCreator
     interval::Int
     solution_variables::SolutionVariables

src/equations/ideal_glm_mhd_multiion_2d.jl

@@ -82,9 +82,9 @@ References:
     In case of more than one ion species, the multi-ion GLM-MHD equations should ALWAYS be used
     with [`source_terms_lorentz`](@ref).
 """
-mutable struct IdealGlmMhdMultiIonEquations2D{NVARS, NCOMP, RealT <: Real,
-                                              ElectronPressure, ElectronTemperature} <:
-               AbstractIdealGlmMhdMultiIonEquations{2, NVARS, NCOMP}
+struct IdealGlmMhdMultiIonEquations2D{NVARS, NCOMP, RealT <: Real,
+                                      ElectronPressure, ElectronTemperature} <:
+       AbstractIdealGlmMhdMultiIonEquations{2, NVARS, NCOMP}
     gammas::SVector{NCOMP, RealT} # Heat capacity ratios
     charge_to_mass::SVector{NCOMP, RealT} # Charge to mass ratios
     gas_constants::SVector{NCOMP, RealT} # Specific gas constants

src/equations/ideal_glm_mhd_multiion_3d.jl

@@ -38,9 +38,9 @@ References:
     In case of more than one ion species, the multi-ion GLM-MHD equations should ALWAYS be used
     with [`source_terms_lorentz`](@ref).
 """
-mutable struct IdealGlmMhdMultiIonEquations3D{NVARS, NCOMP, RealT <: Real,
-                                              ElectronPressure} <:
-               AbstractIdealGlmMhdMultiIonEquations{3, NVARS, NCOMP}
+struct IdealGlmMhdMultiIonEquations3D{NVARS, NCOMP, RealT <: Real,
+                                      ElectronPressure} <:
+       AbstractIdealGlmMhdMultiIonEquations{3, NVARS, NCOMP}
     gammas::SVector{NCOMP, RealT} # Heat capacity ratios
     charge_to_mass::SVector{NCOMP, RealT} # Charge to mass ratios
     electron_pressure::ElectronPressure # Function to compute the electron pressure

src/meshes/dgmulti_meshes.jl

@@ -13,9 +13,9 @@ dispatchable type. This is intended to store geometric data and connectivities f
 mesh (Cartesian, affine, curved, structured/unstructured).
 """
 mutable struct DGMultiMesh{NDIMS, MeshType, MeshDataT <: MeshData{NDIMS}, BoundaryFaceT}
-    md::MeshDataT
+    const md::MeshDataT
 
-    boundary_faces::BoundaryFaceT
+    const boundary_faces::BoundaryFaceT
 
     current_filename :: String
     unsaved_changes  :: Bool

src/meshes/p4est_mesh.jl

@@ -24,17 +24,19 @@ mesh for a two-dimensional surface or shell in three-dimensional space.
 mutable struct P4estMesh{NDIMS, NDIMS_AMBIENT, RealT <: Real, IsParallel, P, Ghost,
                          NDIMSP2, NNODES} <:
                AbstractMesh{NDIMS}
-    p4est       :: P # Either PointerWrapper{p4est_t} or PointerWrapper{p8est_t}
-    is_parallel :: IsParallel
-    ghost       :: Ghost # Either PointerWrapper{p4est_ghost_t} or PointerWrapper{p8est_ghost_t}
+    const p4est::P # Either PointerWrapper{p4est_t} or PointerWrapper{p8est_t}
+    const is_parallel::IsParallel
+    # Either `PointerWrapper{p4est_ghost_t}` or `PointerWrapper{p8est_ghost_t}`.
+    # Required for ghost/halo layers in parallel runs, thus mutable.
+    ghost::Ghost
     # Coordinates at the nodes specified by the tensor product of `nodes` (NDIMS times).
     # This specifies the geometry interpolation for each tree.
-    tree_node_coordinates::Array{RealT, NDIMSP2} # [dimension, i, j, k, tree]
-    nodes::SVector{NNODES, RealT}
-    boundary_names::Array{Symbol, 2}      # [face direction, tree]
+    const tree_node_coordinates::Array{RealT, NDIMSP2} # [dimension, i, j, k, tree]
+    const nodes::SVector{NNODES, RealT}
+    const boundary_names::Array{Symbol, 2} # [face direction, tree]
     current_filename::String
     unsaved_changes::Bool
-    p4est_partition_allow_for_coarsening::Bool
+    const p4est_partition_allow_for_coarsening::Bool
 
     function P4estMesh{NDIMS}(p4est, tree_node_coordinates, nodes, boundary_names,
                               current_filename, unsaved_changes,

src/meshes/p4est_mesh_view.jl

@@ -12,8 +12,8 @@ A view on a [`P4estMesh`](@ref).
 """
 mutable struct P4estMeshView{NDIMS, NDIMS_AMBIENT, RealT <: Real, Parent} <:
                AbstractMesh{NDIMS}
-    parent::Parent
-    cell_ids::Vector{Int}
+    const parent::Parent
+    const cell_ids::Vector{Int}
     unsaved_changes::Bool
     current_filename::String
 end

src/meshes/structured_mesh.jl

@@ -14,10 +14,10 @@ Different numbers of cells per dimension are possible and arbitrary functions
 can be used as domain faces.
 """
 mutable struct StructuredMesh{NDIMS, RealT <: Real} <: AbstractMesh{NDIMS}
-    cells_per_dimension::NTuple{NDIMS, Int}
-    mapping::Any # Not relevant for performance
-    mapping_as_string::String
-    periodicity::NTuple{NDIMS, Bool}
+    const cells_per_dimension::NTuple{NDIMS, Int}
+    const mapping::Any # Not relevant for performance
+    const mapping_as_string::String
+    const periodicity::NTuple{NDIMS, Bool}
     current_filename::String
     unsaved_changes::Bool
 end

src/meshes/structured_mesh_view.jl

@@ -11,13 +11,13 @@
 A view on a structured curved mesh.
 """
 mutable struct StructuredMeshView{NDIMS, RealT <: Real} <: AbstractMesh{NDIMS}
-    parent::StructuredMesh{NDIMS, RealT}
-    cells_per_dimension::NTuple{NDIMS, Int}
-    mapping::Any # Not relevant for performance
-    mapping_as_string::String
+    const parent::StructuredMesh{NDIMS, RealT}
+    const cells_per_dimension::NTuple{NDIMS, Int}
+    const mapping::Any # Not relevant for performance
+    const mapping_as_string::String
     current_filename::String
-    indices_min::NTuple{NDIMS, Int}
-    indices_max::NTuple{NDIMS, Int}
+    const indices_min::NTuple{NDIMS, Int}
+    const indices_max::NTuple{NDIMS, Int}
     unsaved_changes::Bool
 end
 

src/meshes/t8code_mesh.jl

@@ -7,17 +7,17 @@ to manage trees and mesh refinement.
 """
 mutable struct T8codeMesh{NDIMS, RealT <: Real, IsParallel, NDIMSP2, NNODES} <:
                AbstractMesh{NDIMS}
-    forest      :: T8code.ForestWrapper
-    is_parallel :: IsParallel
+    forest::T8code.ForestWrapper
+    const is_parallel::IsParallel
 
     # This specifies the geometry interpolation for each tree.
-    tree_node_coordinates::Array{RealT, NDIMSP2} # [dimension, i, j, k, tree]
+    const tree_node_coordinates::Array{RealT, NDIMSP2} # [dimension, i, j, k, tree]
 
     # Stores the quadrature nodes.
-    nodes::SVector{NNODES, RealT}
+    const nodes::SVector{NNODES, RealT}
 
-    boundary_names   :: Array{Symbol, 2}      # [face direction, tree]
-    current_filename :: String
+    boundary_names::Array{Symbol, 2} # [face direction, tree]
+    current_filename::String
 
     ninterfaces :: Int
     nmortars    :: Int
@@ -35,13 +35,17 @@ mutable struct T8codeMesh{NDIMS, RealT <: Real, IsParallel, NDIMSP2, NNODES} <:
         is_parallel = mpi_isparallel() ? True() : False()
 
         mesh = new{NDIMS, RealT, typeof(is_parallel), NDIMS + 2, length(nodes)}(T8code.ForestWrapper(forest),
-                                                                                is_parallel)
-
-        mesh.nodes = nodes
-        mesh.boundary_names = boundary_names
-        mesh.current_filename = current_filename
-        mesh.tree_node_coordinates = tree_node_coordinates
-        mesh.unsaved_changes = true
+                                                                                is_parallel,
+                                                                                tree_node_coordinates,
+                                                                                nodes,
+                                                                                boundary_names,
+                                                                                current_filename,
+                                                                                -1, # ninterfaces
+                                                                                -1, # nmortars
+                                                                                -1, # nboundaries
+                                                                                -1, # nmpiinterfaces
+                                                                                -1, # nmpimortars
+                                                                                true)
 
         finalizer(mesh) do mesh
             # In serial mode we can finalize the forest right away. In parallel

src/meshes/unstructured_mesh.jl

@@ -18,22 +18,22 @@ from a mesh file `filename`.
 mutable struct UnstructuredMesh2D{RealT <: Real,
                                   CurvedSurfaceT <: CurvedSurface{RealT}} <:
                AbstractMesh{2}
-    filename              :: String
-    n_corners             :: Int
-    n_surfaces            :: Int # total number of surfaces
-    n_interfaces          :: Int # number of interior surfaces
-    n_boundaries          :: Int # number of surfaces on the physical boundary
-    n_elements            :: Int
-    polydeg               :: Int
-    corners               :: Array{RealT, 2}  # [ndims, n_corners]
-    neighbour_information :: Array{Int, 2}  # [neighbour node/element/edge ids, n_surfaces]
-    boundary_names        :: Array{Symbol, 2} # [local sides, n_elements]
-    periodicity           :: Bool
-    element_node_ids      :: Array{Int, 2} # [node ids, n_elements]
-    element_is_curved     :: Vector{Bool}
-    surface_curves        :: Array{CurvedSurfaceT, 2} # [local sides, n_elements]
-    current_filename      :: String
-    unsaved_changes       :: Bool # if true, the mesh will be saved for plotting
+    const filename              :: String
+    const n_corners             :: Int
+    const n_surfaces            :: Int # total number of surfaces
+    const n_interfaces          :: Int # number of interior surfaces
+    const n_boundaries          :: Int # number of surfaces on the physical boundary
+    const n_elements            :: Int
+    const polydeg               :: Int
+    const corners               :: Array{RealT, 2}  # [ndims, n_corners]
+    const neighbour_information :: Array{Int, 2}  # [neighbour node/element/edge ids, n_surfaces]
+    const boundary_names        :: Array{Symbol, 2} # [local sides, n_elements]
+    const periodicity           :: Bool
+    const element_node_ids      :: Array{Int, 2} # [node ids, n_elements]
+    const element_is_curved     :: Vector{Bool}
+    const surface_curves        :: Array{CurvedSurfaceT, 2} # [local sides, n_elements]
+    current_filename            :: String
+    unsaved_changes             :: Bool # if true, the mesh will be saved for plotting
 end
 
 # constructor for an unstructured mesh read in from a file

src/semidiscretization/semidiscretization_coupled.jl

@@ -443,10 +443,10 @@ mutable struct BoundaryConditionCoupled{NDIMS,
                                         uEltype <: Real, Indices, CouplingConverter}
     # NDIMST2M1 == NDIMS * 2 - 1
     # Buffer for boundary values: [variable, nodes_i, nodes_j, cell_i, cell_j]
-    u_boundary         :: Array{uEltype, NDIMST2M1} # NDIMS * 2 - 1
-    other_orientation  :: Int
-    indices            :: Indices
-    coupling_converter :: CouplingConverter
+    u_boundary               :: Array{uEltype, NDIMST2M1} # NDIMS * 2 - 1
+    const other_orientation  :: Int
+    const indices            :: Indices
+    const coupling_converter :: CouplingConverter
 
     function BoundaryConditionCoupled(other_semi_index, indices, uEltype,
                                       coupling_converter)

src/semidiscretization/semidiscretization_hyperbolic.jl

@@ -20,11 +20,11 @@ mutable struct SemidiscretizationHyperbolic{Mesh, Equations, InitialCondition,
 
     # This guy is a bit messy since we abuse it as some kind of "exact solution"
     # although this doesn't really exist...
-    initial_condition::InitialCondition
+    const initial_condition::InitialCondition
 
-    boundary_conditions::BoundaryConditions
-    source_terms::SourceTerms
-    solver::Solver
+    const boundary_conditions::BoundaryConditions
+    const source_terms::SourceTerms
+    const solver::Solver
     cache::Cache
     performance_counter::PerformanceCounter
 end

src/solvers/dgsem_unstructured/sort_boundary_conditions.jl

@@ -8,16 +8,16 @@
 """
     UnstructuredSortedBoundaryTypes
 
-General container to sort the boundary conditions by type and name for some unstructured meshes/solvers.
+General struct to sort the boundary conditions by type and name for some unstructured meshes/solvers.
 It stores a set of global indices for each boundary condition type and name to expedite computation
 during the call to `calc_boundary_flux!`. The original dictionary form of the boundary conditions
 set by the user in the elixir file is also stored for printing.
 """
 mutable struct UnstructuredSortedBoundaryTypes{N, BCs <: NTuple{N, Any},
                                                Vec <: AbstractVector{<:Integer}}
-    boundary_condition_types::BCs # specific boundary condition type(s), e.g. BoundaryConditionDirichlet
+    const boundary_condition_types::BCs # specific boundary condition type(s), e.g. BoundaryConditionDirichlet
     boundary_indices::NTuple{N, Vec} # integer vectors containing global boundary indices
-    boundary_dictionary::Dict{Symbol, Any} # boundary conditions as set by the user in the elixir file
+    const boundary_dictionary::Dict{Symbol, Any} # boundary conditions as set by the user in the elixir file
     boundary_symbol_indices::Dict{Symbol, Vector{Int}} # integer vectors containing global boundary indices per boundary identifier
 end
 

src/time_integration/methods_2N.jl

@@ -77,9 +77,9 @@ end
 # This struct is needed to fake https://github.com/SciML/OrdinaryDiffEq.jl/blob/0c2048a502101647ac35faabd80da8a5645beac7/src/integrators/type.jl#L1
 mutable struct SimpleIntegratorOptions{Callback}
     callback::Callback # callbacks; used in Trixi.jl
-    adaptive::Bool # whether the algorithm is adaptive; ignored
+    const adaptive::Bool # whether the algorithm is adaptive; ignored
     dtmax::Float64 # ignored
-    maxiters::Int # maximal number of time steps
+    const maxiters::Int # maximal number of time steps
     tstops::Vector{Float64} # tstops from https://diffeq.sciml.ai/v6.8/basics/common_solver_opts/#Output-Control-1; ignored
 end
 
@@ -104,8 +104,8 @@ mutable struct SimpleIntegrator2N{RealT <: Real, uType <: AbstractVector,
     iter::Int # current number of time steps (iteration)
     p::Params # will be the semidiscretization from Trixi.jl
     sol::Sol # faked
-    f::F # `rhs!` of the semidiscretization
-    alg::Alg # SimpleAlgorithm2N
+    const f::F # `rhs!` of the semidiscretization
+    const alg::Alg # SimpleAlgorithm2N
     opts::SimpleIntegratorOptions
     finalstep::Bool # added for convenience
 end

src/time_integration/methods_3Sstar.jl

@@ -143,8 +143,8 @@ mutable struct SimpleIntegrator3Sstar{RealT <: Real, uType <: AbstractVector,
     iter::Int # current number of time step (iteration)
     p::Params # will be the semidiscretization from Trixi.jl
     sol::Sol # faked
-    f::F # `rhs!` of the semidiscretization
-    alg::Alg # SimpleAlgorithm3Sstar
+    const f::F # `rhs!` of the semidiscretization
+    const alg::Alg # SimpleAlgorithm3Sstar
     opts::SimpleIntegratorOptions
     finalstep::Bool # added for convenience
 end