message: Add tile mapping
  Reviewers: jakeh, davidn, stephenm, romand
diff: @@ -184,7 +184,7 @@ void MultiUpdateInternal(poplar::Graph& graph, poplar::Tensor operand,
  } else {
  poplar::Tensor scale = graph.addConstant(operand.elementType(), {}, 1,
  debug_prefix + "/const_1_scale");
  -
  + graph.setTileMapping(scale, 0);
  popops::multiUpdateAdd(
  graph, operand, adjusted_canonical_updates,
  canonical_scatter_iIndices.reinterpret(poplar::UNSIGNED_INT), scale,
  