message: Request tile pairs.
  Summary:
  Fixes T43234
  Depends on D48974
  Reviewers: #tensorflow, simonl, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep
  Maniphest Tasks: T43234
diff: @@ -680,7 +680,8 @@ absl::optional<Tilesets> PartitionTiles(const poplar::Graph& main_graph,
  const auto num_compute_tiles = num_tiles_per_ipu - num_io_tiles;
  const auto compute_tiles =
  - gcl::perIPUTiles(main_graph, num_io_tiles, num_compute_tiles);
  + gcl::perIPUTiles(main_graph, num_io_tiles, num_compute_tiles,
  + /*sorted=*/true, /*tilePairs=*/true);
  CHECK_EQ(compute_tiles.size(), num_compute_tiles);
  const auto io_tiles = DisjointTiles(compute_tiles, num_tiles_per_ipu);
  