1 /* Copyright 2021 The TensorFlow Authors. All Rights Reserved. 2 3 Licensed under the Apache License, Version 2.0 (the "License"); 4 you may not use this file except in compliance with the License. 5 You may obtain a copy of the License at 6 7 http://www.apache.org/licenses/LICENSE-2.0 8 9 Unless required by applicable law or agreed to in writing, software 10 distributed under the License is distributed on an "AS IS" BASIS, 11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 See the License for the specific language governing permissions and 13 limitations under the License. 14 ==============================================================================*/ 15 16 #ifndef TENSORFLOW_COMPILER_XLA_SERVICE_GPU_ALL_REDUCE_BLUECONNECT_H_ 17 #define TENSORFLOW_COMPILER_XLA_SERVICE_GPU_ALL_REDUCE_BLUECONNECT_H_ 18 19 #include "tensorflow/compiler/xla/service/hlo_module.h" 20 #include "tensorflow/compiler/xla/service/hlo_pass_interface.h" 21 #include "tensorflow/compiler/xla/statusor.h" 22 23 namespace xla { 24 25 // Decomposes all-reduce operations using the BlueConnect algorithm. 26 // 27 // Paper: "BLUECONNECT: DECOMPOSING ALL-REDUCE FOR DEEP LEARNING ON 28 // HETEROGENEOUS NETWORK HIERARCHY" 29 // https://mlsys.org/Conferences/2019/doc/2019/130.pdf 30 // 31 // This algorithm attempts to minimize the number of levels of network hierarchy 32 // traversed for as much data transfer as possible. This implementation assumes 33 // that host IDs are ordered corresponding to network hierarchy. 34 class AllReduceBlueConnect : public HloModulePass { 35 public: AllReduceBlueConnect(size_t num_devices_per_host)36 explicit AllReduceBlueConnect(size_t num_devices_per_host) 37 : num_devices_per_host_(num_devices_per_host) {} 38 name()39 absl::string_view name() const override { return "all-reduce-blueconnect"; } 40 41 using HloPassInterface::Run; 42 StatusOr<bool> Run( 43 HloModule* module, 44 const absl::flat_hash_set<absl::string_view>& execution_threads) override; 45 46 private: 47 size_t num_devices_per_host_; 48 }; 49 50 } // namespace xla 51 52 #endif // TENSORFLOW_COMPILER_XLA_SERVICE_GPU_ALL_REDUCE_BLUECONNECT_H_ 53