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

Reviewed By: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep

Maniphest Tasks: T43234

Differential Revision: https://phabricator.sourcevertex.net/D48975

Author: jakeh-gc

tensorflow/compiler/plugin/poplar/driver/poplar_compiler.cc

@@ -678,7 +678,8 @@ 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);