From 301950c4c4bf864eb1816602c05bbd7f13f39348 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lars=20G=C3=B6ttgens?= <lars.goettgens@rwth-aachen.de>
Date: Fri, 20 Dec 2024 15:07:17 +0100
Subject: [PATCH] Add serialization for `WeightLattice`

---
 src/Serialization/LieTheory.jl  | 42 +++++++++++++++
 test/Serialization/LieTheory.jl | 92 +++++++++++++++++++++++++++------
 2 files changed, 119 insertions(+), 15 deletions(-)

diff --git a/src/Serialization/LieTheory.jl b/src/Serialization/LieTheory.jl
index b696c86ec87..2d06aa6769f 100644
--- a/src/Serialization/LieTheory.jl
+++ b/src/Serialization/LieTheory.jl
@@ -62,6 +62,48 @@ function load_type_params(
   return load_typed_object(s)
 end
 
+###############################################################################
+#
+#   Weight lattices
+#
+###############################################################################
+
+@register_serialization_type WeightLattice uses_id
+
+function save_object(s::SerializerState, P::WeightLattice)
+  save_data_dict(s) do
+    save_typed_object(s, root_system(P), :root_system)
+  end
+end
+
+function load_object(s::DeserializerState, ::Type{WeightLattice})
+  R = load_typed_object(s, :root_system)
+  return weight_lattice(R)
+end
+
+@register_serialization_type WeightLatticeElem uses_params
+
+function save_object(s::SerializerState, w::WeightLatticeElem)
+  save_object(s, _vec(coefficients(w)))
+end
+
+function load_object(s::DeserializerState, ::Type{WeightLatticeElem}, P::WeightLattice)
+  return WeightLatticeElem(P, load_object(s, Vector, ZZ))
+end
+
+function save_type_params(s::SerializerState, w::WeightLatticeElem)
+  save_data_dict(s) do
+    save_object(s, encode_type(typeof(w)), :name)
+    parent_w = parent(w)
+    parent_ref = save_as_ref(s, parent_w)
+    save_object(s, parent_ref, :params)
+  end
+end
+
+function load_type_params(s::DeserializerState, ::Type{WeightLatticeElem})
+  return load_typed_object(s)
+end
+
 ###############################################################################
 #
 #   Weyl groups
diff --git a/test/Serialization/LieTheory.jl b/test/Serialization/LieTheory.jl
index 9cee6151044..29363274698 100644
--- a/test/Serialization/LieTheory.jl
+++ b/test/Serialization/LieTheory.jl
@@ -27,7 +27,7 @@
           # nothing, cause `R === loaded` anyway
         end
 
-        if n_roots(R) >= 1
+        if rank(R) >= 1
           r = positive_root(R, n_positive_roots(R))
           test_save_load_roundtrip(path, r) do loaded
             @test root_system(loaded) === R
@@ -59,25 +59,87 @@
       end
     end
 
-    @testset "WeylGroup" begin
+    @testset "WeightLattice" begin
       @testset "simple saving and loading" begin
-        W = weyl_group((:A, 2), (:B, 4))
+        for R in [
+          root_system(zero_matrix(ZZ, 0, 0)), # rk 0
+          root_system((:A, 2), (:B, 4)),
+        ]
+          P = weight_lattice(R)
+
+          test_save_load_roundtrip(path, P) do loaded
+            # nothing, cause `P === loaded` anyway
+          end
 
-        test_save_load_roundtrip(path, W) do loaded
-          # nothing, cause `W === loaded` anyway
-        end
+          w = WeightLatticeElem(P, [rand(ZZ, -10:10) for _ in 1:rank(P)])
+          test_save_load_roundtrip(path, w) do loaded
+            @test parent(loaded) === P
+            @test coefficients(loaded) == coefficients(w)
+          end
 
-        x = rand(W)
-        test_save_load_roundtrip(path, x) do loaded
-          @test parent(loaded) === W
-          @test word(loaded) == word(x)
+          test_save_load_roundtrip(path, gens(P)) do loaded
+            @test length(loaded) == rank(P)
+            @test all(coefficients(loaded[i]) == coefficients(gen(P, i)) for i in 1:rank(R))
+          end
         end
+      end
 
-        test_save_load_roundtrip(path, gens(W)) do loaded
-          @test length(loaded) == ngens(W)
-          @test all(
-            word(loaded[i]) == word(gen(W, i)) for i in 1:ngens(W)
-          )
+      @testset "cyclic reference between R and P survives" begin
+        Oscar.reset_global_serializer_state()
+
+        R_filename = joinpath(path, "R.mrdi")
+        P_filename = joinpath(path, "P.mrdi")
+
+        R = root_system(:D, 5)
+        P = weight_lattice(R)
+
+        save(R_filename, R)
+        save(P_filename, P)
+
+        Oscar.reset_global_serializer_state()
+
+        loaded_R = load(R_filename)
+        loaded_P = load(P_filename)
+
+        @test loaded_R === root_system(loaded_P)
+        @test loaded_P === weight_lattice(loaded_R)
+
+        loaded_R = loaded_P = nothing # unset all references
+
+        Oscar.reset_global_serializer_state()
+
+        loaded_P = load(P_filename)
+        loaded_R = load(R_filename)
+
+        @test loaded_R === root_system(loaded_P)
+        @test loaded_P === weight_lattice(loaded_R)
+
+        loaded_R = loaded_P = nothing # unset all references        
+      end
+    end
+
+    @testset "WeylGroup" begin
+      @testset "simple saving and loading" begin
+        for W in [
+          weyl_group(zero_matrix(ZZ, 0, 0)), # rk 0
+          weyl_group((:A, 2), (:B, 4)),
+        ]
+          test_save_load_roundtrip(path, W) do loaded
+            # nothing, cause `W === loaded` anyway
+          end
+
+          x = rand(W)
+          test_save_load_roundtrip(path, x) do loaded
+            @test parent(loaded) === W
+            @test word(loaded) == word(x)
+          end
+
+          test_save_load_roundtrip(path, gens(W)) do loaded
+            @test length(loaded) == ngens(W)
+            @test all(
+              word(loaded[i]) == word(gen(W, i)) for i in 1:ngens(W)
+            )
+          end
         end
       end