Add tool to find interfaces connecting 2 patches

This MR addresses the third point in #360

See merge request gysela-developpers/gyselalibxx!712

--------------------------------------------

src/multipatch/connectivity/connectivity.hpp

@@ -32,23 +32,32 @@ class MultipatchConnectivity
             "Missing edges. There should be 4 edges for each patch.");
 
     /**
-     * @brief A tool to find a type sequence of all patches directly connected (via an interface)
-     * to the patch.
+     * @brief A tool to find a type sequence of all interfaces of a patch.
      *
      * @tparam QueryPatch The patch whose connections we are interested in.
      */
     template <class QueryPatch>
-    using get_type_seq_connections_t = direct_patch_connections_t<QueryPatch, interface_collection>;
+    using get_type_seq_connections_t = interfaces_of_patch_t<QueryPatch, interface_collection>;
 
     /**
-     * @brief A tool to find a tuple of all patches directly connected (via an interface) to
-     * the patch.
+     * @brief A tool to find a tuple of all interfaces of a patch.
      *
      * @tparam QueryPatch The patch whose connections we are interested in.
      */
     template <class QueryPatch>
     using get_connections_t = to_tuple_t<get_type_seq_connections_t<QueryPatch>>;
 
+    /**
+     * @brief A tool to find all interfaces linking 2 patches.
+     *
+     * @tparam QueryPatch1 The first patch.
+     * @tparam QueryPatch2 The second patch.
+     */
+    template <class QueryPatch1, class QueryPatch2>
+    using find_connections_t = ddcHelper::type_seq_intersection_t<
+            get_type_seq_connections_t<QueryPatch1>,
+            get_type_seq_connections_t<QueryPatch2>>;
+
     /**
      * @brief A function to return all index ranges which can be used to obtain coordinates
      * along a line which passes through the requested grid.

src/multipatch/connectivity/connectivity_details.hpp

@@ -450,9 +450,9 @@ using strip_outside_edges_t =
 template <class EdgeTypeSeq>
 using extract_patches_t = typename connectivity_details::ExtractPatches<EdgeTypeSeq>::type;
 
-/// A tool to find all patches directly connected to the start patch via an interface.
+/// A tool to find all interfaces directly connected to the start patch.
 template <class StartPatch, class InterfaceTypeSeq>
-using direct_patch_connections_t =
+using interfaces_of_patch_t =
         typename connectivity_details::PatchConnection<StartPatch, InterfaceTypeSeq>::type;
 
 /// A tool to find a patch which contains the specified grid.

src/utils/ddc_helper.hpp

@@ -301,6 +301,39 @@ struct ApplyTemplateToTypeSeq<Templ, ddc::detail::TypeSeq<Tags...>>
 {
     using type = ddc::detail::TypeSeq<Templ<Tags>...>;
 };
+
+/// R contains all elements that are in A and B.
+/// Remark 1: This operation preserves the order from B.
+/// Remark 2: It is similar to the set intersection in the set theory.
+/// Example: A = [a, b, c], B = [z, c, y], R = [c]
+template <class TagSeqA, class TagSeqB, class TagSeqR>
+struct TypeSeqIntersection;
+
+template <class TypeSeqA, class TypeSeqR>
+struct TypeSeqIntersection<TypeSeqA, ddc::detail::TypeSeq<>, TypeSeqR>
+{
+    using type = TypeSeqR;
+};
+
+template <class TypeSeqA, class HeadTagsB, class... TailTagsB, class... TagsR>
+struct TypeSeqIntersection<
+        TypeSeqA,
+        ddc::detail::TypeSeq<HeadTagsB, TailTagsB...>,
+        ddc::detail::TypeSeq<TagsR...>>
+{
+    using type = std::conditional_t<
+            ddc::in_tags_v<HeadTagsB, TypeSeqA>,
+            typename TypeSeqIntersection<
+                    TypeSeqA,
+                    ddc::detail::TypeSeq<TailTagsB...>,
+                    ddc::detail::TypeSeq<TagsR..., HeadTagsB>>::type,
+            typename TypeSeqIntersection<
+                    TypeSeqA,
+                    ddc::detail::TypeSeq<TailTagsB...>,
+                    ddc::detail::TypeSeq<TagsR...>>::type>;
+};
+
+
 /// \endcond
 
 } // namespace detail
@@ -332,4 +365,9 @@ namespace ddcHelper {
 /// A helper to get a type sequence by applying a template to a sequence of type tags.
 template <template <class Tag> class Templ, class TypeSeq>
 using apply_template_to_type_seq_t = typename detail::ApplyTemplateToTypeSeq<Templ, TypeSeq>::type;
+
+/// A helper to find all types which are found in both TypeSeq1 and TypeSeq2
+template <class TypeSeq1, class TypeSeq2>
+using type_seq_intersection_t =
+        typename detail::TypeSeqIntersection<TypeSeq1, TypeSeq2, ddc::detail::TypeSeq<>>::type;
 } // namespace ddcHelper

tests/multipatch/connectivity/multipatch_connectivity.cpp

@@ -104,6 +104,28 @@ TEST(MultipatchConnectivityTest, GetConnections)
     EXPECT_TRUE((ddc::in_tags_v<Interface_4_5, Patch5Interfaces>));
 }
 
+TEST(MultipatchConnectivityTest, FindConnections)
+{
+    using namespace periodic_strips_uniform_2d_9patches;
+    EXPECT_TRUE((std::is_same_v<
+                 typename Connectivity::template find_connections_t<Patch1, Patch2>,
+                 ddc::detail::TypeSeq<Interface_1_2>>));
+    EXPECT_TRUE((std::is_same_v<
+                 typename Connectivity::template find_connections_t<Patch1, Patch5>,
+                 ddc::detail::TypeSeq<>>));
+    EXPECT_TRUE((std::is_same_v<
+                 typename Connectivity::template find_connections_t<Patch7, Patch9>,
+                 ddc::detail::TypeSeq<Interface_9_7>>));
+}
+
+TEST(MultipatchConnectivityTest, FindConnections2)
+{
+    using namespace figure_of_eight_5patches;
+    using Interfaces_1_2 = typename Connectivity::template find_connections_t<Patch1, Patch2>;
+    EXPECT_TRUE((ddc::in_tags_v<LoopInterface_2_1, Interfaces_1_2>));
+    EXPECT_TRUE((ddc::in_tags_v<EightInterface_2_1, Interfaces_1_2>));
+}
+
 TEST(MultipatchConnectivityTest, GetAllIndexRangesAlongDim)
 {
     using namespace periodic_strips_uniform_2d_9patches;