From 0bc91844ae3144890601fb211970b1da35be2d4e Mon Sep 17 00:00:00 2001
From: JordiManyer <jordi.manyer@monash.edu>
Date: Tue, 17 Sep 2024 15:10:32 +1000
Subject: [PATCH] Added ConstantFESpaces

---
 src/FESpaces.jl               | 19 +++++++++++++++++++
 test/ConstantFESpacesTests.jl | 27 +++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 test/ConstantFESpacesTests.jl

diff --git a/src/FESpaces.jl b/src/FESpaces.jl
index c2b0947..5bb0dff 100644
--- a/src/FESpaces.jl
+++ b/src/FESpaces.jl
@@ -869,3 +869,22 @@ function _compute_new_distributed_fixedval(
   c = reduce(+,c_i,init=zero(eltype(c_i)))
   return c
 end
+
+function FESpaces.ConstantFESpace(model::DistributedDiscreteModel;kwargs...)
+  @warn "ConstantFESpace is NOT scalable in parallel. For testing purposes only."
+  spaces = map(local_views(model)) do model
+    ConstantFESpace(model;kwargs...)
+  end
+
+  # Single dof, owned by processor 1 (ghost for all other processors)
+  cell_gids = get_cell_gids(model)
+  indices = map(partition(cell_gids)) do cell_indices
+    me = part_id(cell_indices)
+    LocalIndices(1,me,Int[1],Int32[1])
+  end
+  gids = PRange(indices)
+
+  trian = DistributedTriangulation(map(get_triangulation,spaces),model)
+  vector_type = _find_vector_type(spaces,gids)
+  return DistributedSingleFieldFESpace(spaces,gids,trian,vector_type)
+end
diff --git a/test/ConstantFESpacesTests.jl b/test/ConstantFESpacesTests.jl
new file mode 100644
index 0000000..f0bbcea
--- /dev/null
+++ b/test/ConstantFESpacesTests.jl
@@ -0,0 +1,27 @@
+
+using Gridap
+using GridapDistributed, PartitionedArrays
+
+using Gridap.FESpaces
+
+np = (2,2)
+ranks = with_debug() do distribute
+  distribute(LinearIndices((prod(np),)))
+end
+
+model = CartesianDiscreteModel(ranks,np,(0,1,0,1),(4,4))
+
+Ω = Triangulation(model)
+dΩ = Measure(Ω,2)
+
+V = ConstantFESpace(model)
+
+gids = get_free_dof_ids(V)
+local_to_global(gids)
+local_to_owner(gids)
+ghost_to_local(gids)
+own_to_local(gids)
+
+uh = zero(V)
+sum(∫(uh)dΩ)
+