Use enum instead of symbols for indexing

examples/structured_2d_dgsem/elixir_advection_coupled.jl

@@ -1,5 +1,6 @@
 using OrdinaryDiffEq
 using Trixi
+import Trixi.Indexing
 
 ###############################################################################
 # Coupled semidiscretization of four linear advection systems using converter functions such that
@@ -61,13 +62,13 @@ coupling_function12 = (x, u, equations_other, equations_own) -> u
 coupling_function13 = (x, u, equations_other, equations_own) -> u
 
 # Define the coupling boundary conditions and the system it is coupled to.
-boundary_conditions_x_neg1 = BoundaryConditionCoupled(2, (:end, :i_forward), Float64,
+boundary_conditions_x_neg1 = BoundaryConditionCoupled(2, (Indexing.last, Indexing.i_forward), Float64,
                                                       coupling_function12)
-boundary_conditions_x_pos1 = BoundaryConditionCoupled(2, (:begin, :i_forward), Float64,
+boundary_conditions_x_pos1 = BoundaryConditionCoupled(2, (Indexing.first, Indexing.i_forward), Float64,
                                                       coupling_function12)
-boundary_conditions_y_neg1 = BoundaryConditionCoupled(3, (:i_forward, :end), Float64,
+boundary_conditions_y_neg1 = BoundaryConditionCoupled(3, (Indexing.i_forward, Indexing.last), Float64,
                                                       coupling_function13)
-boundary_conditions_y_pos1 = BoundaryConditionCoupled(3, (:i_forward, :begin), Float64,
+boundary_conditions_y_pos1 = BoundaryConditionCoupled(3, (Indexing.i_forward, Indexing.first), Float64,
                                                       coupling_function13)
 
 # A semidiscretization collects data structures and functions for the spatial discretization
@@ -93,13 +94,13 @@ coupling_function21 = (x, u, equations_other, equations_own) -> u
 coupling_function24 = (x, u, equations_other, equations_own) -> u
 
 # Define the coupling boundary conditions and the system it is coupled to.
-boundary_conditions_x_neg2 = BoundaryConditionCoupled(1, (:end, :i_forward), Float64,
+boundary_conditions_x_neg2 = BoundaryConditionCoupled(1, (Indexing.last, Indexing.i_forward), Float64,
                                                       coupling_function21)
-boundary_conditions_x_pos2 = BoundaryConditionCoupled(1, (:begin, :i_forward), Float64,
+boundary_conditions_x_pos2 = BoundaryConditionCoupled(1, (Indexing.first, Indexing.i_forward), Float64,
                                                       coupling_function21)
-boundary_conditions_y_neg2 = BoundaryConditionCoupled(4, (:i_forward, :end), Float64,
+boundary_conditions_y_neg2 = BoundaryConditionCoupled(4, (Indexing.i_forward, Indexing.last), Float64,
                                                       coupling_function24)
-boundary_conditions_y_pos2 = BoundaryConditionCoupled(4, (:i_forward, :begin), Float64,
+boundary_conditions_y_pos2 = BoundaryConditionCoupled(4, (Indexing.i_forward, Indexing.first), Float64,
                                                       coupling_function24)
 
 # A semidiscretization collects data structures and functions for the spatial discretization
@@ -125,13 +126,13 @@ coupling_function34 = (x, u, equations_other, equations_own) -> u
 coupling_function31 = (x, u, equations_other, equations_own) -> u
 
 # Define the coupling boundary conditions and the system it is coupled to.
-boundary_conditions_x_neg3 = BoundaryConditionCoupled(4, (:end, :i_forward), Float64,
+boundary_conditions_x_neg3 = BoundaryConditionCoupled(4, (Indexing.last, Indexing.i_forward), Float64,
                                                       coupling_function34)
-boundary_conditions_x_pos3 = BoundaryConditionCoupled(4, (:begin, :i_forward), Float64,
+boundary_conditions_x_pos3 = BoundaryConditionCoupled(4, (Indexing.first, Indexing.i_forward), Float64,
                                                       coupling_function34)
-boundary_conditions_y_neg3 = BoundaryConditionCoupled(1, (:i_forward, :end), Float64,
+boundary_conditions_y_neg3 = BoundaryConditionCoupled(1, (Indexing.i_forward, Indexing.last), Float64,
                                                       coupling_function31)
-boundary_conditions_y_pos3 = BoundaryConditionCoupled(1, (:i_forward, :begin), Float64,
+boundary_conditions_y_pos3 = BoundaryConditionCoupled(1, (Indexing.i_forward, Indexing.first), Float64,
                                                       coupling_function31)
 
 # A semidiscretization collects data structures and functions for the spatial discretization
@@ -157,13 +158,13 @@ coupling_function43 = (x, u, equations_other, equations_own) -> u
 coupling_function42 = (x, u, equations_other, equations_own) -> u
 
 # Define the coupling boundary conditions and the system it is coupled to.
-boundary_conditions_x_neg4 = BoundaryConditionCoupled(3, (:end, :i_forward), Float64,
+boundary_conditions_x_neg4 = BoundaryConditionCoupled(3, (Indexing.last, Indexing.i_forward), Float64,
                                                       coupling_function43)
-boundary_conditions_x_pos4 = BoundaryConditionCoupled(3, (:begin, :i_forward), Float64,
+boundary_conditions_x_pos4 = BoundaryConditionCoupled(3, (Indexing.first, Indexing.i_forward), Float64,
                                                       coupling_function43)
-boundary_conditions_y_neg4 = BoundaryConditionCoupled(2, (:i_forward, :end), Float64,
+boundary_conditions_y_neg4 = BoundaryConditionCoupled(2, (Indexing.i_forward, Indexing.last), Float64,
                                                       coupling_function42)
-boundary_conditions_y_pos4 = BoundaryConditionCoupled(2, (:i_forward, :begin), Float64,
+boundary_conditions_y_pos4 = BoundaryConditionCoupled(2, (Indexing.i_forward, Indexing.first), Float64,
                                                       coupling_function42)
 
 # A semidiscretization collects data structures and functions for the spatial discretization

examples/structured_2d_dgsem/elixir_advection_meshview.jl

@@ -51,21 +51,21 @@ mesh2 = StructuredMeshView(parent_mesh; indices_min = (9, 1), indices_max = (16,
 coupling_function = (x, u, equations_other, equations_own) -> u
 
 # Define the coupled boundary conditions
-# The indices (:end, :i_forward) and (:begin, :i_forward) denote the interface indexing.
+# The indices (Indexing.last, Indexing.i_forward) and (Indexing.first, Indexing.i_forward) denote the interface indexing.
 # For a system with coupling in x and y see examples/structured_2d_dgsem/elixir_advection_coupled.jl.
 boundary_conditions1 = (
                         # Connect left boundary with right boundary of left mesh
-                        x_neg = BoundaryConditionCoupled(2, (:end, :i_forward), Float64,
+                        x_neg = BoundaryConditionCoupled(2, (Indexing.last, Indexing.i_forward), Float64,
                                                          coupling_function),
-                        x_pos = BoundaryConditionCoupled(2, (:begin, :i_forward), Float64,
+                        x_pos = BoundaryConditionCoupled(2, (Indexing.first, Indexing.i_forward), Float64,
                                                          coupling_function),
                         y_neg = boundary_condition_periodic,
                         y_pos = boundary_condition_periodic)
 boundary_conditions2 = (
                         # Connect left boundary with right boundary of left mesh
-                        x_neg = BoundaryConditionCoupled(1, (:end, :i_forward), Float64,
+                        x_neg = BoundaryConditionCoupled(1, (Indexing.last, Indexing.i_forward), Float64,
                                                          coupling_function),
-                        x_pos = BoundaryConditionCoupled(1, (:begin, :i_forward), Float64,
+                        x_pos = BoundaryConditionCoupled(1, (Indexing.first, Indexing.i_forward), Float64,
                                                          coupling_function),
                         y_neg = boundary_condition_periodic,
                         y_pos = boundary_condition_periodic)

examples/structured_2d_dgsem/elixir_mhd_coupled.jl

@@ -49,9 +49,9 @@ mesh1 = StructuredMesh(cells_per_dimension,
                        periodicity = (false, true))
 
 coupling_function1 = (x, u, equations_other, equations_own) -> u
-boundary_conditions1 = (x_neg = BoundaryConditionCoupled(2, (:end, :i_forward), Float64,
+boundary_conditions1 = (x_neg = BoundaryConditionCoupled(2, (Indexing.last, Indexing.i_forward), Float64,
                                                          coupling_function1),
-                        x_pos = BoundaryConditionCoupled(2, (:begin, :i_forward), Float64,
+                        x_pos = BoundaryConditionCoupled(2, (Indexing.first, Indexing.i_forward), Float64,
                                                          coupling_function1),
                         y_neg = boundary_condition_periodic,
                         y_pos = boundary_condition_periodic)
@@ -72,9 +72,9 @@ mesh2 = StructuredMesh(cells_per_dimension,
                        periodicity = (false, true))
 
 coupling_function2 = (x, u, equations_other, equations_own) -> u
-boundary_conditions2 = (x_neg = BoundaryConditionCoupled(1, (:end, :i_forward), Float64,
+boundary_conditions2 = (x_neg = BoundaryConditionCoupled(1, (Indexing.last, Indexing.i_forward), Float64,
                                                          coupling_function2),
-                        x_pos = BoundaryConditionCoupled(1, (:begin, :i_forward), Float64,
+                        x_pos = BoundaryConditionCoupled(1, (Indexing.first, Indexing.i_forward), Float64,
                                                          coupling_function2),
                         y_neg = boundary_condition_periodic,
                         y_pos = boundary_condition_periodic)

src/semidiscretization/semidiscretization_coupled.jl

@@ -452,11 +452,11 @@ mutable struct BoundaryConditionCoupled{NDIMS,
         NDIMS = length(indices)
         u_boundary = Array{uEltype, NDIMS * 2 - 1}(undef, ntuple(_ -> 0, NDIMS * 2 - 1))
 
-        if indices[1] in (:begin, :end)
+        if indices[1] in (Indexing.first, Indexing.last)
             other_orientation = 1
-        elseif indices[2] in (:begin, :end)
+        elseif indices[2] in (Indexing.first, Indexing.last)
             other_orientation = 2
-        else # indices[3] in (:begin, :end)
+        else # indices[3] in (Indexing.first, Indexing.last)
             other_orientation = 3
         end
 

src/solvers/dg.jl

@@ -752,6 +752,33 @@ function compute_coefficients!(u, func, t, mesh::AbstractMesh{3}, equations, dg:
     end
 end
 
+end # @muladd; put it up here because module definition below needs to be at top level
+
+# For some mesh types, elements next to a surface may have local coordinate systems
+# that are not aligned so the nodes may have to be indexed differently.
+# `IndexInfo` is used to describe how the nodes should be indexed.
+# For example, in 2d a `Tuple` with two `IndexInfo` objects, one for each dimension,
+# would be used.
+# `first` or `last` indicates that the corresponding index is constant and is either
+# the first or the last one. This effectively encodes the position of the surface
+# with respect to the local coordinate system. The other `IndexInfo` object(s)
+# encode if the index in the corresponding dimension is running forward or backward.
+#
+# The Enum is wrapped in a module and exported so that the enum values do not pollute
+# the global namespace and can only be accessed via `Indexing.value`.
+module Indexing
+@enum IndexInfo begin
+    first
+    last
+    i_forward
+    i_backward
+    j_forward
+    j_backward
+end
+export IndexInfo
+end
+using .Indexing
+
 # Discretizations specific to each mesh type of Trixi.jl
 # If some functionality is shared by multiple combinations of meshes/solvers,
 # it is defined in the directory of the most basic mesh and solver type.
@@ -765,4 +792,3 @@ include("dgsem_structured/dg.jl")
 include("dgsem_unstructured/dg.jl")
 include("dgsem_p4est/dg.jl")
 include("dgsem_t8code/dg.jl")
-end # @muladd

src/solvers/dgsem_p4est/containers.jl

@@ -131,12 +131,12 @@ mutable struct P4estInterfaceContainer{NDIMS, uEltype <: Real, NDIMSP2} <:
                AbstractContainer
     u::Array{uEltype, NDIMSP2}       # [primary/secondary, variable, i, j, interface]
     neighbor_ids::Matrix{Int}                   # [primary/secondary, interface]
-    node_indices::Matrix{NTuple{NDIMS, Symbol}} # [primary/secondary, interface]
+    node_indices::Matrix{NTuple{NDIMS, IndexInfo}} # [primary/secondary, interface]
 
     # internal `resize!`able storage
     _u::Vector{uEltype}
     _neighbor_ids::Vector{Int}
-    _node_indices::Vector{NTuple{NDIMS, Symbol}}
+    _node_indices::Vector{NTuple{NDIMS, IndexInfo}}
 end
 
 @inline function ninterfaces(interfaces::P4estInterfaceContainer)
@@ -184,7 +184,7 @@ function init_interfaces(mesh::Union{P4estMesh, T8codeMesh}, equations, basis, e
     _neighbor_ids = Vector{Int}(undef, 2 * n_interfaces)
     neighbor_ids = unsafe_wrap(Array, pointer(_neighbor_ids), (2, n_interfaces))
 
-    _node_indices = Vector{NTuple{NDIMS, Symbol}}(undef, 2 * n_interfaces)
+    _node_indices = Vector{NTuple{NDIMS, IndexInfo}}(undef, 2 * n_interfaces)
     node_indices = unsafe_wrap(Array, pointer(_node_indices), (2, n_interfaces))
 
     interfaces = P4estInterfaceContainer{NDIMS, uEltype, NDIMS + 2}(u, neighbor_ids,
@@ -207,7 +207,7 @@ mutable struct P4estBoundaryContainer{NDIMS, uEltype <: Real, NDIMSP1} <:
                AbstractContainer
     u::Array{uEltype, NDIMSP1}       # [variables, i, j, boundary]
     neighbor_ids::Vector{Int}                   # [boundary]
-    node_indices::Vector{NTuple{NDIMS, Symbol}} # [boundary]
+    node_indices::Vector{NTuple{NDIMS, IndexInfo}} # [boundary]
     name::Vector{Symbol}                # [boundary]
 
     # internal `resize!`able storage
@@ -257,7 +257,7 @@ function init_boundaries(mesh::Union{P4estMesh, T8codeMesh}, equations, basis, e
                      n_boundaries))
 
     neighbor_ids = Vector{Int}(undef, n_boundaries)
-    node_indices = Vector{NTuple{NDIMS, Symbol}}(undef, n_boundaries)
+    node_indices = Vector{NTuple{NDIMS, IndexInfo}}(undef, n_boundaries)
     names = Vector{Symbol}(undef, n_boundaries)
 
     boundaries = P4estBoundaryContainer{NDIMS, uEltype, NDIMS + 1}(u, neighbor_ids,
@@ -338,12 +338,12 @@ mutable struct P4estMortarContainer{NDIMS, uEltype <: Real, NDIMSP1, NDIMSP3} <:
                AbstractContainer
     u::Array{uEltype, NDIMSP3} # [small/large side, variable, position, i, j, mortar]
     neighbor_ids::Matrix{Int}             # [position, mortar]
-    node_indices::Matrix{NTuple{NDIMS, Symbol}} # [small/large, mortar]
+    node_indices::Matrix{NTuple{NDIMS, IndexInfo}} # [small/large, mortar]
 
     # internal `resize!`able storage
     _u::Vector{uEltype}
     _neighbor_ids::Vector{Int}
-    _node_indices::Vector{NTuple{NDIMS, Symbol}}
+    _node_indices::Vector{NTuple{NDIMS, IndexInfo}}
 end
 
 @inline nmortars(mortars::P4estMortarContainer) = size(mortars.neighbor_ids, 2)
@@ -391,7 +391,7 @@ function init_mortars(mesh::Union{P4estMesh, T8codeMesh}, equations, basis, elem
     neighbor_ids = unsafe_wrap(Array, pointer(_neighbor_ids),
                                (2^(NDIMS - 1) + 1, n_mortars))
 
-    _node_indices = Vector{NTuple{NDIMS, Symbol}}(undef, 2 * n_mortars)
+    _node_indices = Vector{NTuple{NDIMS, IndexInfo}}(undef, 2 * n_mortars)
     node_indices = unsafe_wrap(Array, pointer(_node_indices), (2, n_mortars))
 
     mortars = P4estMortarContainer{NDIMS, uEltype, NDIMS + 1, NDIMS + 3}(u,
@@ -706,17 +706,17 @@ end
 
 # Return direction of the face, which is indexed by node_indices
 @inline function indices2direction(indices)
-    if indices[1] === :begin
+    if indices[1] === Indexing.first
         return 1
-    elseif indices[1] === :end
+    elseif indices[1] === Indexing.last
         return 2
-    elseif indices[2] === :begin
+    elseif indices[2] === Indexing.first
         return 3
-    elseif indices[2] === :end
+    elseif indices[2] === Indexing.last
         return 4
-    elseif indices[3] === :begin
+    elseif indices[3] === Indexing.first
         return 5
-    else # if indices[3] === :end
+    else # if indices[3] === Indexing.last
         return 6
     end
 end

src/solvers/dgsem_p4est/containers_2d.jl

@@ -95,24 +95,24 @@ end
         # relative to the interface.
         if side == 1 || orientation == 0
             # Forward indexing
-            i = :i_forward
+            i = Indexing.i_forward
         else
             # Backward indexing
-            i = :i_backward
+            i = Indexing.i_backward
         end
 
         if faces[side] == 0
             # Index face in negative x-direction
-            interfaces.node_indices[side, interface_id] = (:begin, i)
+            interfaces.node_indices[side, interface_id] = (Indexing.first, i)
         elseif faces[side] == 1
             # Index face in positive x-direction
-            interfaces.node_indices[side, interface_id] = (:end, i)
+            interfaces.node_indices[side, interface_id] = (Indexing.last, i)
         elseif faces[side] == 2
             # Index face in negative y-direction
-            interfaces.node_indices[side, interface_id] = (i, :begin)
+            interfaces.node_indices[side, interface_id] = (i, Indexing.first)
         else # faces[side] == 3
             # Index face in positive y-direction
-            interfaces.node_indices[side, interface_id] = (i, :end)
+            interfaces.node_indices[side, interface_id] = (i, Indexing.last)
         end
     end
 
@@ -124,16 +124,16 @@ end
                                              face, boundary_id)
     if face == 0
         # Index face in negative x-direction
-        boundaries.node_indices[boundary_id] = (:begin, :i_forward)
+        boundaries.node_indices[boundary_id] = (Indexing.first, Indexing.i_forward)
     elseif face == 1
         # Index face in positive x-direction
-        boundaries.node_indices[boundary_id] = (:end, :i_forward)
+        boundaries.node_indices[boundary_id] = (Indexing.last, Indexing.i_forward)
     elseif face == 2
         # Index face in negative y-direction
-        boundaries.node_indices[boundary_id] = (:i_forward, :begin)
+        boundaries.node_indices[boundary_id] = (Indexing.i_forward, Indexing.first)
     else # face == 3
         # Index face in positive y-direction
-        boundaries.node_indices[boundary_id] = (:i_forward, :end)
+        boundaries.node_indices[boundary_id] = (Indexing.i_forward, Indexing.last)
     end
 
     return boundaries
@@ -148,24 +148,24 @@ end
         # relative to the mortar.
         if side == 1 || orientation == 0
             # Forward indexing for small side or orientation == 0
-            i = :i_forward
+            i = Indexing.i_forward
         else
             # Backward indexing for large side with reversed orientation
-            i = :i_backward
+            i = Indexing.i_backward
         end
 
         if faces[side] == 0
             # Index face in negative x-direction
-            mortars.node_indices[side, mortar_id] = (:begin, i)
+            mortars.node_indices[side, mortar_id] = (Indexing.first, i)
         elseif faces[side] == 1
             # Index face in positive x-direction
-            mortars.node_indices[side, mortar_id] = (:end, i)
+            mortars.node_indices[side, mortar_id] = (Indexing.last, i)
         elseif faces[side] == 2
             # Index face in negative y-direction
-            mortars.node_indices[side, mortar_id] = (i, :begin)
+            mortars.node_indices[side, mortar_id] = (i, Indexing.first)
         else # faces[side] == 3
             # Index face in positive y-direction
-            mortars.node_indices[side, mortar_id] = (i, :end)
+            mortars.node_indices[side, mortar_id] = (i, Indexing.last)
         end
     end