[pgm] review updates:

- documentation
- refactor

Co-authored-by: Fritz Goebel <fritz.goebel@tum.de>
Co-authored-by: Yu-Hsiang M. Tsai <yhmtsai@gmail.com>u

core/distributed/matrix.cpp

@@ -236,15 +236,15 @@ Matrix<ValueType, LocalIndexType, GlobalIndexType>::create(
     array<comm_index_type> part_ids(exec->get_master(), comm.size());
     std::iota(part_ids.get_data(), part_ids.get_data() + part_ids.get_size(),
               0);
-    auto uniform_partition =
+    auto contiguous_partition =
         share(build_partition_from_local_size<LocalIndexType, GlobalIndexType>(
             exec, comm, local_linop->get_size()[0]));
     array<global_index_type> global_recv_gather_idxs(
         exec, recv_gather_idxs.get_size());
     for (int rank = 0; rank < comm.size(); ++rank) {
         if (recv_sizes[rank] > 0) {
             auto map = index_map<LocalIndexType, GlobalIndexType>(
-                exec, uniform_partition, rank, array<GlobalIndexType>{exec});
+                exec, contiguous_partition, rank, array<GlobalIndexType>{exec});
             auto local_view = make_array_view(
                 exec, recv_sizes[rank],
                 recv_gather_idxs.get_data() + recv_offsets[rank]);
@@ -258,7 +258,7 @@ Matrix<ValueType, LocalIndexType, GlobalIndexType>::create(
     return Matrix::create(
         exec, comm,
         index_map<LocalIndexType, GlobalIndexType>(
-            exec, uniform_partition, comm.rank(), global_recv_gather_idxs),
+            exec, contiguous_partition, comm.rank(), global_recv_gather_idxs),
         std::move(local_linop), std::move(non_local_linop));
 }
 

core/multigrid/pgm.cpp

@@ -281,7 +281,7 @@ array<GlobalIndexType> Pgm<ValueType, IndexType>::communicate_non_local_agg(
     // local indices to global
     experimental::distributed::index_map<IndexType, GlobalIndexType> imap(
         exec, coarse_partition, comm.rank(), array<GlobalIndexType>{exec});
-    auto seng_global_agg = imap.map_to_global(
+    auto send_global_agg = imap.map_to_global(
         send_agg, experimental::distributed::index_space::local);
 
     array<GlobalIndexType> non_local_agg(exec, total_recv_size);
@@ -293,13 +293,13 @@ array<GlobalIndexType> Pgm<ValueType, IndexType>::communicate_non_local_agg(
         host_recv_buffer.resize_and_reset(total_recv_size);
         host_send_buffer.resize_and_reset(total_send_size);
         exec->get_master()->copy_from(exec, total_send_size,
-                                      seng_global_agg.get_data(),
+                                      send_global_agg.get_data(),
                                       host_send_buffer.get_data());
     }
     auto type = experimental::mpi::type_impl<GlobalIndexType>::get_type();
 
     const auto send_ptr = use_host_buffer ? host_send_buffer.get_const_data()
-                                          : seng_global_agg.get_const_data();
+                                          : send_global_agg.get_const_data();
     auto recv_ptr = use_host_buffer ? host_recv_buffer.get_data()
                                     : non_local_agg.get_data();
     exec->synchronize();
@@ -396,7 +396,7 @@ void Pgm<ValueType, IndexType>::generate()
                 // the coarse partition will have only one range per part
                 // and only one part per rank.
                 // The global indices are ordered block-wise by rank, i.e. rank
-                // 1 owns [0, ..., N_1), rank 2 [N_1, ..., N_2), ...
+                // 0 owns [0, ..., N_1), rank 1 [N_1, ..., N_2), ...
                 auto coarse_local_size =
                     static_cast<int64>(std::get<1>(result)->get_size()[0]);
                 auto coarse_partition = gko::share(

include/ginkgo/core/multigrid/pgm.hpp

@@ -205,7 +205,7 @@ class Pgm : public EnableLinOp<Pgm<ValueType, IndexType>>,
      * @param local_agg  the local aggregate indices
      *
      * @return  the aggregates for non-local columns. The aggregated indices are
-     *          in the new global indexing
+     *          in the new global indexing for the coarse matrix
      */
     template <typename GlobalIndexType>
     array<GlobalIndexType> communicate_non_local_agg(

test/mpi/matrix.cpp

@@ -386,6 +386,7 @@ TYPED_TEST(MatrixCreation, BuildFromExistingData)
     GKO_ASSERT_MTX_NEAR(y->get_local_vector(), result[rank], 0);
 }
 
+
 #endif