shad uses operator== instead of Equal

[NanmiaoWu]

• The issue is: shad should use HandleTrait::Equal, but it uses operator==.

• The detailed error info is shown as follow:

  (base) nanmiao@jiujiu:~/Documents/my_project/src/SHAD/build_hpx_Debug$ make -j 10
  [  2%] Built target cpp_simple_runtime
  [  5%] Built target runtime
  Scanning dependencies of target util
  Scanning dependencies of target ei-sssp
  Scanning dependencies of target shadtest_main
  Scanning dependencies of target page-rank
  Scanning dependencies of target pi
  Scanning dependencies of target triangle-count
  Scanning dependencies of target ei-triangle-count
  Scanning dependencies of target ei-page-rank
  Scanning dependencies of target ei-vertex_nomination
  Scanning dependencies of target blackscholes
  [  7%] Building CXX object src/util/CMakeFiles/util.dir/shad.cc.o
  [  8%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-sssp.dir/ei-sssp.cc.o
  [ 10%] Building CXX object examples/array/CMakeFiles/page-rank.dir/page-rank.cc.o
  [ 11%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-page-rank.dir/ei-page-rank.cc.o
  [ 13%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-triangle-count.dir/ei-triangle-count.cc.o
  [ 14%] Building CXX object examples/blackscholes/CMakeFiles/blackscholes.dir/blackscholes.cc.o
  [ 16%] Building CXX object test/unit_tests/CMakeFiles/shadtest_main.dir/gtest_main.cc.o
  [ 17%] Building CXX object examples/pi/CMakeFiles/pi.dir/pi.cc.o
  [ 19%] Building CXX object examples/array/CMakeFiles/triangle-count.dir/triangle-count.cc.o
  [ 20%] Building CXX object examples/edge_index_graph/CMakeFiles/ei-vertex_nomination.dir/ei-vertex_nomination.cc.o
  In file included from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/runtime/runtime.h:42,
               from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/data_structures/object_identifier.h:30,
               from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/data_structures/abstract_data_structure.h:35,
               from /home/nanmiao/Documents/my_project/src/SHAD/include/shad/core/array.h:30,
               from /home/nanmiao/Documents/my_project/src/SHAD/examples/pi/pi.cc:29:
  /home/nanmiao/Documents/my_project/src/SHAD/include/shad/runtime/handle.h: In member function ‘bool shad::rt::Handle::IsNull() const’:
  /home/nanmiao/Documents/my_project/src/SHAD/include/shad/runtime/handle.h:90:16: error: no match for ‘operator==’ (operand types are ‘const HandleTy’ {aka ‘const hpx::lcos::shared_future<void>’} and ‘shad::rt::impl::HandleTrait<shad::rt::impl::hpx_tag>::HandleTy’ {aka ‘hpx::lcos::shared_future<void>’})
  90 |     return id_ == impl::HandleTrait<TargetSystemTag>::NullValue();
    |            ~~~ ^~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    |            |                                                   |
    |            shared_future<[...]>                                shared_future<[...]>

• The issue happens when I update HandleTrait in hpx_traits_mapping as follow

  template <>
  struct HandleTrait<hpx_tag> {
  using HandleTy = hpx::shared_future<void>;
  using ParameterTy = hpx::shared_future<void> &;
  using ConstParameterTy = const hpx::shared_future<void> &;
  
  static void Init(ParameterTy H, ConstParameterTy V) {
  H = V.then([](HandleTy&&){});
  }
  
  static HandleTy NullValue() { return hpx::shared_future<void>(); }
  
  static bool Equal(ConstParameterTy lhs, ConstParameterTy rhs) {
  return toUnsignedInt(lhs) == toUnsignedInt(rhs);
  }
  
  static std::string toString(ConstParameterTy H) {
  return std::to_string(toUnsignedInt(H));
  }
  
  static uint64_t toUnsignedInt(ConstParameterTy H) {
  return reinterpret_cast<uint64_t>(hpx::traits::detail::get_shared_state(H).get());
  }
  
  static HandleTy CreateNewHandle() { return hpx::shared_future<void>(); }
  
  static void WaitFor(ParameterTy H) { if (H.valid()) H.get(); }
  };

[NanmiaoWu]

A workaround to this issue is: change IsNull() as follows:

  bool IsNull() const {
      return impl::HandleTrait<TargetSystemTag>::Equal(id_, impl::HandleTrait<TargetSystemTag>::NullValue());
  }