Silence spurious compiler warnings (#3913)

We see compiler warnings basically saying some internal data member in `std::optional` may be used uninitialized. This lengthy warnings are very annoying and can hide important warnings/errors.

Seeing https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635, it seems like this warning is not valid and due to the fact that the compiler cannot perfectly track when an `std::optional` object is valid or not in every code path.

Anyways, this PR tweaks the code to silence the warnings. There is very little practical difference between the old and new code, but I don't see the annoying warnings anymore with this update.

See the below for the actual warnings.
```
[1/1] Building CUDA object CMakeFiles/cugraph.dir/src/structure/graph_view_mg.cu.o
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<GraphViewType, T>::edge_src_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, true, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:425:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((const std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<GraphViewType, T>::edge_src_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, true, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:425:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(long unsigned int*)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_size_.std::optional<long unsigned int>::<unnamed>.std::_Optional_base<long unsigned int, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>& cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>::operator=(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:375:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>& cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>::operator=(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:375:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>& cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>::operator=(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:375:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>,cugraph::edge_src_property_t<cugraph::graph_view_t<int, int, true, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = false; GraphViewType = cugraph::graph_view_t<int, int, true, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, true, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, true, true>, 1> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:522:20: note: '<anonymous>' declared here
  522 |       minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<GraphViewType, T>::edge_dst_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, false, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:527:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((const std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<GraphViewType, T>::edge_dst_property_t(const raft::handle_t&, const GraphViewType&) [with GraphViewType = cugraph::graph_view_t<int, int, false, true>; T = int]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:527:13,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(long unsigned int*)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_size_.std::optional<long unsigned int>::<unnamed>.std::_Optional_base<long unsigned int, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>& cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>::operator=(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:467:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::keys_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>& cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>::operator=(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:467:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '*(const int**)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::<unnamed>))' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'cugraph::detail::edge_minor_property_t<int, int>& cugraph::detail::edge_minor_property_t<int, int>::operator=(cugraph::detail::edge_minor_property_t<int, int>&&)',
    inlined from 'cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>& cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>::operator=(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true>, int>&&)' at /home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:467:7,
    inlined from 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]' at /home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:18:
/home/seunghwak/RAPIDS/development/cugraph/cpp/include/cugraph/edge_src_dst_property.hpp:285:7: warning: '((std::size_t*)((char*)&<unnamed> + offsetof(cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>,cugraph::edge_dst_property_t<cugraph::graph_view_t<int, int, false, true, void>, int>::property_.cugraph::detail::edge_minor_property_t<int, int>::key_chunk_start_offsets_.std::optional<raft::span<const int, true, 18446744073709551615> >::<unnamed>.std::_Optional_base<raft::span<const int, true, 18446744073709551615>, true, true>::_M_payload.std::_Optional_payload<raft::span<const int, true, 18446744073709551615>, true, true, true>::<unnamed>.std::_Optional_payload_base<raft::span<const int, true, 18446744073709551615> >::_M_payload)))[1]' may be used uninitialized [-Wmaybe-uninitialized]
  285 | class edge_minor_property_t {
      |       ^~~~~~~~~~~~~~~~~~~~~
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh: In function 'void cugraph::detail::per_v_transform_reduce_e(const raft::handle_t&, const GraphViewType&, EdgeSrcValueInputWrapper, EdgeDstValueInputWrapper, EdgeValueInputWrapper, EdgeOp, T, ReduceOp, VertexValueOutputIterator) [with bool incoming = true; GraphViewType = cugraph::graph_view_t<int, int, false, true>; EdgeSrcValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeDstValueInputWrapper = cugraph::detail::edge_endpoint_dummy_property_view_t; EdgeValueInputWrapper = cugraph::edge_dummy_property_view_t; EdgeOp = __nv_dl_wrapper_t<__nv_dl_tag<rmm::device_uvector<int> (*)(const raft::handle_t&, const cugraph::graph_view_t<int, int, false, true>&), cugraph::_GLOBAL__N__fbd7e12b_16_graph_view_mg_cu_854a5764_83484::compute_minor_degrees<int, int, false, true>, 2> >; ReduceOp = cugraph::reduce_op::plus<int>; T = int; VertexValueOutputIterator = int*]':
/home/seunghwak/RAPIDS/development/cugraph/cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh:524:20: note: '<anonymous>' declared here
  524 |       minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

Authors:
  - Seunghwa Kang (https://github.com/seunghwak)
  - Chuck Hastings (https://github.com/ChuckHastings)

Approvers:
  - Chuck Hastings (https://github.com/ChuckHastings)
  - Naim (https://github.com/naimnv)

URL: #3913

cpp/src/prims/per_v_transform_reduce_incoming_outgoing_e.cuh

@@ -513,24 +513,20 @@ void per_v_transform_reduce_e(raft::handle_t const& handle,
 
   static_assert(is_arithmetic_or_thrust_tuple_of_arithmetic<T>::value);
 
-  [[maybe_unused]] std::conditional_t<GraphViewType::is_storage_transposed,
-                                      edge_src_property_t<GraphViewType, T>,
-                                      edge_dst_property_t<GraphViewType, T>>
-    minor_tmp_buffer(handle);  // relevant only when (GraphViewType::is_multi_gpu && !update_major
+  using minor_tmp_buffer_type = std::conditional_t<GraphViewType::is_storage_transposed,
+                                                   edge_src_property_t<GraphViewType, T>,
+                                                   edge_dst_property_t<GraphViewType, T>>;
+  [[maybe_unused]] std::unique_ptr<minor_tmp_buffer_type> minor_tmp_buffer{};
   if constexpr (GraphViewType::is_multi_gpu && !update_major) {
-    if constexpr (GraphViewType::is_storage_transposed) {
-      minor_tmp_buffer = edge_src_property_t<GraphViewType, T>(handle, graph_view);
-    } else {
-      minor_tmp_buffer = edge_dst_property_t<GraphViewType, T>(handle, graph_view);
-    }
+    minor_tmp_buffer = std::make_unique<minor_tmp_buffer_type>(handle, graph_view);
   }
 
   using edge_partition_minor_output_device_view_t =
-    std::conditional_t<update_major,
-                       void /* dummy */,
+    std::conditional_t<GraphViewType::is_multi_gpu && !update_major,
                        detail::edge_partition_endpoint_property_device_view_t<
                          vertex_t,
-                         decltype(minor_tmp_buffer.mutable_view().value_first())>>;
+                         decltype(minor_tmp_buffer->mutable_view().value_first())>,
+                       void /* dummy */>;
 
   if constexpr (update_major) {
     size_t partition_idx = 0;
@@ -549,7 +545,7 @@ void per_v_transform_reduce_e(raft::handle_t const& handle,
   } else {
     if constexpr (GraphViewType::is_multi_gpu) {
       auto minor_init = init;
-      auto view       = minor_tmp_buffer.view();
+      auto view       = minor_tmp_buffer->view();
       if (view.keys()) {  // defer applying the initial value to the end as minor_tmp_buffer may not
                           // store values for the entire minor range
         minor_init = ReduceOp::identity_element;
@@ -558,7 +554,7 @@ void per_v_transform_reduce_e(raft::handle_t const& handle,
         auto const major_comm_rank = major_comm.get_rank();
         minor_init                 = (major_comm_rank == 0) ? init : ReduceOp::identity_element;
       }
-      fill_edge_minor_property(handle, graph_view, minor_init, minor_tmp_buffer.mutable_view());
+      fill_edge_minor_property(handle, graph_view, minor_init, minor_tmp_buffer->mutable_view());
     } else {
       thrust::fill(handle.get_thrust_policy(),
                    vertex_value_output_first,
@@ -699,7 +695,7 @@ void per_v_transform_reduce_e(raft::handle_t const& handle,
       if constexpr (update_major) {
         output_buffer = major_buffer_first;
       } else {
-        output_buffer = edge_partition_minor_output_device_view_t(minor_tmp_buffer.mutable_view());
+        output_buffer = edge_partition_minor_output_device_view_t(minor_tmp_buffer->mutable_view());
       }
     } else {
       output_buffer = vertex_value_output_first;
@@ -913,7 +909,7 @@ void per_v_transform_reduce_e(raft::handle_t const& handle,
     auto const minor_comm_rank = minor_comm.get_rank();
     auto const minor_comm_size = minor_comm.get_size();
 
-    auto view = minor_tmp_buffer.view();
+    auto view = minor_tmp_buffer->view();
     if (view.keys()) {  // applying the initial value is deferred to here
       vertex_t max_vertex_partition_size{0};
       for (int i = 0; i < major_comm_size; ++i) {