[dist] revert coll-comm creator function

Author: MarcelKoch

core/distributed/dense_communicator.cpp

@@ -110,16 +110,15 @@ request DenseCommunicator::i_all_to_all_v_impl(
 }
 
 
-CollectiveCommunicator::creator_fn DenseCommunicator::creator_with_same_type()
-    const
+std::unique_ptr<CollectiveCommunicator>
+DenseCommunicator::create_with_same_type(communicator base,
+                                         index_map_ptr imap) const
 {
-    return [](communicator base, index_map_ptr imap) {
-        return std::visit(
-            [base](auto imap_) {
-                return std::make_unique<DenseCommunicator>(base, *imap_);
-            },
-            imap);
-    };
+    return std::visit(
+        [base](const auto* imap) {
+            return std::make_unique<DenseCommunicator>(base, *imap);
+        },
+        imap);
 }
 
 

core/distributed/matrix.cpp

@@ -101,8 +101,9 @@ Matrix<ValueType, LocalIndexType, GlobalIndexType>::Matrix(
 
     row_gatherer_ = RowGatherer<LocalIndexType>::create(
         row_gatherer_->get_executor(),
-        row_gatherer_->get_collective_communicator()->creator_with_same_type(),
-        comm, imap_);
+        row_gatherer_->get_collective_communicator()->create_with_same_type(
+            comm, &imap_),
+        imap_);
 }
 
 
@@ -340,8 +341,9 @@ void Matrix<ValueType, LocalIndexType, GlobalIndexType>::read_distributed(
 
     row_gatherer_ = RowGatherer<LocalIndexType>::create(
         row_gatherer_->get_executor(),
-        row_gatherer_->get_collective_communicator()->creator_with_same_type(),
-        comm, imap_);
+        row_gatherer_->get_collective_communicator()->create_with_same_type(
+            comm, &imap_),
+        imap_);
 }
 
 

core/distributed/neighborhood_communicator.cpp

@@ -156,17 +156,16 @@ request NeighborhoodCommunicator::i_all_to_all_v_impl(
 }
 
 
-CollectiveCommunicator::creator_fn
-NeighborhoodCommunicator::creator_with_same_type() const
+std::unique_ptr<CollectiveCommunicator>
+NeighborhoodCommunicator::create_with_same_type(communicator base,
+                                                index_map_ptr imap) const
 {
-    return [](communicator base, index_map_ptr imap) {
-        return std::visit(
-            [base](auto imap_) {
-                return std::unique_ptr<CollectiveCommunicator>(
-                    std::make_unique<NeighborhoodCommunicator>(base, *imap_));
-            },
-            imap);
-    };
+    return std::visit(
+        [base](const auto* imap) {
+            return std::unique_ptr<CollectiveCommunicator>(
+                new NeighborhoodCommunicator(base, *imap));
+        },
+        imap);
 }
 
 

include/ginkgo/core/distributed/collective_communicator.hpp

@@ -38,13 +38,6 @@ class CollectiveCommunicator {
                      const distributed::index_map<int32, int64>*,
                      const distributed::index_map<int64, int64>*>;
 
-    /**
-     * Creator function to create a new CollectiveCommunicator from a
-     * communicator and a pointer to an index_map.
-     */
-    using creator_fn = std::function<std::unique_ptr<CollectiveCommunicator>(
-        communicator, index_map_ptr)>;
-
     virtual ~CollectiveCommunicator() = default;
 
     explicit CollectiveCommunicator(communicator base = MPI_COMM_NULL);
@@ -81,10 +74,15 @@ class CollectiveCommunicator {
                            void* recv_buffer, MPI_Datatype recv_type) const;
 
     /**
-     * Returns a CollectiveCommunicator::creator_fn which will create a new
-     * CollectiveCommunicator with the same dynamic type.
+     * Creates a new CollectiveCommunicator with the same dynamic type.
+     *
+     * @param base  The base communicator
+     * @param imap  The index_map that defines the communication pattern
+     *
+     * @return  a CollectiveCommunicator with the same dynamic type
      */
-    [[nodiscard]] virtual creator_fn creator_with_same_type() const = 0;
+    [[nodiscard]] virtual std::unique_ptr<CollectiveCommunicator>
+    create_with_same_type(communicator base, index_map_ptr imap) const = 0;
 
     /**
      * Creates a CollectiveCommunicator with the inverse communication pattern
@@ -97,16 +95,16 @@ class CollectiveCommunicator {
     create_inverse() const = 0;
 
     /**
-     * Get the total number of received elements this communication patterns
-     * expects.
+     * Get the number of elements received by this process within this
+     * communication pattern.
      *
      * @return  number of received elements.
      */
     [[nodiscard]] virtual comm_index_type get_recv_size() const = 0;
 
     /**
-     * Get the total number of sent elements this communication patterns
-     * expects.
+     * Get the number of elements sent by this process within this communication
+     * pattern.
      *
      * @return  number of sent elements.
      */

include/ginkgo/core/distributed/dense_communicator.hpp

@@ -64,7 +64,8 @@ class DenseCommunicator final : public CollectiveCommunicator {
         communicator base,
         const distributed::index_map<LocalIndexType, GlobalIndexType>& imap);
 
-    [[nodiscard]] creator_fn creator_with_same_type() const override;
+    [[nodiscard]] std::unique_ptr<CollectiveCommunicator> create_with_same_type(
+        communicator base, index_map_ptr imap) const override;
 
     /**
      * Creates the inverse DenseCommunicator by switching sources

include/ginkgo/core/distributed/neighborhood_communicator.hpp

@@ -68,7 +68,8 @@ class NeighborhoodCommunicator final : public CollectiveCommunicator {
         communicator base,
         const distributed::index_map<LocalIndexType, GlobalIndexType>& imap);
 
-    creator_fn creator_with_same_type() const override;
+    std::unique_ptr<CollectiveCommunicator> create_with_same_type(
+        communicator base, index_map_ptr imap) const override;
 
     /**
      * Creates the inverse NeighborhoodCommunicator by switching sources

include/ginkgo/core/distributed/row_gatherer.hpp

@@ -128,33 +128,31 @@ class RowGatherer final
      * @tparam GlobalIndexType  the global index type of the index map
      *
      * @param exec  the executor
-     * @param coll_comm_creator  the collective communicator creator_fn
+     * @param coll_comm  the collective communicator
      * @param imap  the index map defining which rows to gather
      *
+     * @note The coll_comm and imap have to be compatible. The coll_comm must
+     *       send and recv exactly as many rows as the imap defines.
+     *
      * @return  a shared_ptr to the created distributed::RowGatherer
      */
     template <typename GlobalIndexType = int64,
               typename = std::enable_if_t<sizeof(GlobalIndexType) >=
                                           sizeof(LocalIndexType)>>
     static std::unique_ptr<RowGatherer> create(
         std::shared_ptr<const Executor> exec,
-        mpi::CollectiveCommunicator::creator_fn coll_comm_creator,
-        mpi::communicator base_comm,
+        std::shared_ptr<const mpi::CollectiveCommunicator> coll_comm,
         const index_map<LocalIndexType, GlobalIndexType>& imap)
     {
-        return std::unique_ptr<RowGatherer>(new RowGatherer(
-            std::move(exec), coll_comm_creator(base_comm, &imap), imap));
+        return std::unique_ptr<RowGatherer>(
+            new RowGatherer(std::move(exec), std::move(coll_comm), imap));
     }
 
     /*
      * Create method for an empty RowGatherer.
      */
     static std::unique_ptr<RowGatherer> create(
-        std::shared_ptr<const Executor> exec, mpi::communicator comm)
-    {
-        return std::unique_ptr<RowGatherer>(
-            new RowGatherer(std::move(exec), std::move(comm)));
-    }
+        std::shared_ptr<const Executor> exec, mpi::communicator comm);
 
     RowGatherer(const RowGatherer& o);