--- a/src/SbpOperators/volumeops/volume_operator.jl	Mon May 23 07:20:27 2022 +0200
+++ b/src/SbpOperators/volumeops/volume_operator.jl	Tue Feb 10 22:41:19 2026 +0100
@@ -1,47 +1,28 @@
-"""
-    volume_operator(grid, inner_stencil, closure_stencils, parity, direction)
-
-Creates a volume operator on a `Dim`-dimensional grid acting along the
-specified coordinate `direction`. The action of the operator is determined by
-the stencils `inner_stencil` and `closure_stencils`. When `Dim=1`, the
-corresponding `VolumeOperator` tensor mapping is returned. When `Dim>1`, the
-returned operator is the appropriate outer product of a one-dimensional
-operators and `IdentityTensor`s, e.g for `Dim=3` the volume operator in the
-y-direction is `I⊗op⊗I`.
-"""
-function volume_operator(grid::EquidistantGrid, inner_stencil, closure_stencils, parity, direction)
-    #TODO: Check that direction <= Dim?
-
-    # Create 1D volume operator in along coordinate direction
-    op = VolumeOperator(restrict(grid, direction), inner_stencil, closure_stencils, parity)
-    # Create 1D IdentityTensors for each coordinate direction
-    one_d_grids = restrict.(Ref(grid), Tuple(1:dimension(grid)))
-    Is = IdentityTensor{eltype(grid)}.(size.(one_d_grids))
-    # Formulate the correct outer product sequence of the identity mappings and
-    # the volume operator
-    parts = Base.setindex(Is, op, direction)
-    return foldl(⊗, parts)
-end
-
 """
     VolumeOperator{T,N,M,K} <: LazyTensor{T,1,1}
-Implements a one-dimensional constant coefficients volume operator
+
+A one-dimensional constant coefficients stencil operator.
 """
 struct VolumeOperator{T,N,M,K} <: LazyTensor{T,1,1}
     inner_stencil::Stencil{T,N}
     closure_stencils::NTuple{M,Stencil{T,K}}
-    size::NTuple{1,Int}
+    size::Int
     parity::Parity
+
+    function VolumeOperator(inner_stencil::Stencil{T,N}, closure_stencils::Tuple{Stencil{T,K}, Vararg{Stencil{T,K}}}, size::Int, parity::Parity) where {T,N,K}
+        M = length(closure_stencils)
+        return new{T,N,M,K}(inner_stencil, closure_stencils, size, parity)
+    end
 end
 
-function VolumeOperator(grid::EquidistantGrid{1}, inner_stencil, closure_stencils, parity)
-    return VolumeOperator(inner_stencil, Tuple(closure_stencils), size(grid), parity)
-end
+function VolumeOperator(grid::EquidistantGrid, inner_stencil, closure_stencils, parity)
+    return VolumeOperator(inner_stencil, Tuple(closure_stencils), size(grid,1), parity)
+end # TBD: Remove this function?
 
 closure_size(::VolumeOperator{T,N,M}) where {T,N,M} = M
 
-LazyTensors.range_size(op::VolumeOperator) = op.size
-LazyTensors.domain_size(op::VolumeOperator) = op.size
+LazyTensors.range_size(op::VolumeOperator) = (op.size,)
+LazyTensors.domain_size(op::VolumeOperator) = (op.size,)
 
 function LazyTensors.apply(op::VolumeOperator, v::AbstractVector, i::Index{Lower})
     return @inbounds apply_stencil(op.closure_stencils[Int(i)], v, Int(i))
@@ -52,10 +33,11 @@
 end
 
 function LazyTensors.apply(op::VolumeOperator, v::AbstractVector, i::Index{Upper})
-    return @inbounds Int(op.parity)*apply_stencil_backwards(op.closure_stencils[op.size[1]-Int(i)+1], v, Int(i))
+    return @inbounds Int(op.parity)*apply_stencil_backwards(op.closure_stencils[op.size-Int(i)+1], v, Int(i))
 end
 
 function LazyTensors.apply(op::VolumeOperator, v::AbstractVector, i)
-    r = getregion(i, closure_size(op), op.size[1])
+    r = getregion(i, closure_size(op), op.size)
     return LazyTensors.apply(op, v, Index(i, r))
 end
+# TODO: Move this to LazyTensors when we have the region communication down.