message: [XLA:GPU] Add more logging to nccl_all_reduce_thunk.
diff: @@ -577,12 +577,20 @@ Status NcclAllReduceThunk::ExecuteOnStream(const ExecuteParams& params) {
  RendezvousKey rendezvous_key = RendezvousKey::FromInstruction(
  params.run_id, global_devices, local_devices.size(), hlo_instruction());
  + if (VLOG_IS_ON(2)) {
  + std::vector<std::string> local_participants;
  + for (const auto& entry : local_devices) {
  + local_participants.push_back(absl::StrFormat(
  + "global=%d/local=%d", entry.first.value(), entry.second));
  + }
  VLOG(2) << "Rendezvous key: " << rendezvous_key.ToString()
  << ", global participating replicas: "
  << absl::StrJoin(global_participating_replicas, ", ")
  << ", global participating devices: "
  - << GlobalDeviceIdsToString(global_devices);
  -
  + << GlobalDeviceIdsToString(global_devices)
  + << ", local participants: "
  + << absl::StrJoin(local_participants, ",");
  + }
  AllReduceParticipantData participant(rendezvous_key);
  participant.device_ordinal = local_device_ordinal;
  for (size_t i = 0; i < buffers_.size(); ++i) {
  