Remove scale loss before reduce in dygraph (#30807)

paddle/fluid/imperative/CMakeLists.txt

@@ -12,7 +12,7 @@ if(NOT WIN32)
     if(WITH_NCCL)
         cc_library(imperative_all_reduce SRCS all_reduce.cc DEPS collective_helper device_context selected_rows tensor)
         cc_library(nccl_context SRCS nccl_context.cc DEPS collective_helper device_context imperative_all_reduce var_type_traits)
-        cc_library(reducer SRCS reducer.cc DEPS layer imperative_all_reduce)
+        nv_library(reducer SRCS reducer.cc reducer.cu DEPS layer imperative_all_reduce)
     endif()
     if(WITH_XPU_BKCL)
         cc_library(bkcl_context SRCS bkcl_context.cc DEPS collective_helper device_context tensor var_type_traits)

paddle/fluid/imperative/parallel_context.h

@@ -66,6 +66,8 @@ class ParallelContext {
 
   inline int GetNRings() const { return strategy_.nrings_; }
 
+  inline int64_t GetNRanks() const { return strategy_.nranks_; }
+
  protected:
   ParallelStrategy strategy_;
   platform::Place place_;

paddle/fluid/imperative/reducer.cc

@@ -28,6 +28,29 @@ namespace paddle {
 namespace imperative {
 
 #if (defined PADDLE_WITH_NCCL) || (defined PADDLE_WITH_XPU_BKCL)
+// div the nranks
+void Group::DivNRanks(const platform::DeviceContext &context, int64_t nranks) {
+  framework::Tensor *tensor =
+      is_sparse_
+          ? sparse_contents_->GetMutable<framework::SelectedRows>()
+                ->mutable_value()
+          : dense_contents_.GetMutable<framework::LoDTensor>();
+
+  if (platform::is_gpu_place(tensor->place())) {
+#if defined(PADDLE_WITH_NCCL)
+    DivNRanks(tensor, nranks, context);
+#endif
+  } else if (platform::is_cpu_place(tensor->place())) {
+    framework::VisitDataTypeSmall(
+        dtype_, DivNRanksForAllReduce<platform::CPUDeviceContext>(
+                    tensor, nranks, context));
+  } else if (platform::is_xpu_place(tensor->place())) {
+#ifdef PADDLE_WITH_XPU_BKCL
+// TODO(liuyuhui) support xpu about div nranks in the future
+#endif
+  }
+}
+
 template <typename DeviceContext, typename T>
 static void ConcatTensorsForAllReduce(
     const DeviceContext &context,
@@ -276,6 +299,7 @@ Reducer::Reducer(const std::vector<std::shared_ptr<imperative::VarBase>> &vars,
       find_unused_vars_(find_unused_vars) {
   VLOG(3) << "Start construct the Reducer ...";
   nrings_ = parallel_ctx->GetNRings();
+  nranks_ = parallel_ctx->GetNRanks();
   // initialize groups
   InitializeGroups(group_indices);
   for (size_t global_var_index = 0; global_var_index < vars_.size();
@@ -444,7 +468,7 @@ void Reducer::PrepareForBackward(
   PADDLE_ENFORCE_EQ(
       all_group_ready_, false,
       platform::errors::PreconditionNotMet(
-          "Please note that all ``forward`` outputs derived from the module "
+          "Please note that all forward outputs derived from the module "
           "parameters must participate in the calculation of losses and "
           "subsequent gradient calculations. If not, the wrapper will hang, "
           "waiting for autograd to generate gradients for these parameters. "
@@ -631,6 +655,7 @@ void Reducer::MarkGroupReady(size_t group_index) {
       if (group.sparse_contents_ != nullptr) {
         VLOG(3) << "sparse group [" << next_group_
                 << "] start allreduce in ring[" << run_order << "]";
+        group.DivNRanks(*parallel_ctx_->GetDeviceContext(run_order), nranks_);
         parallel_ctx_->AllReduceByStream(
             *group.sparse_contents_, group.sparse_contents_, run_order, false);
       } else {
@@ -654,6 +679,7 @@ void Reducer::MarkGroupReady(size_t group_index) {
         parallel_ctx_->WaitComm(run_order);
       }
 #endif
+      group.DivNRanks(*parallel_ctx_->GetDeviceContext(run_order), nranks_);
 
       // Start allreduce
       parallel_ctx_->AllReduceByStream(

paddle/fluid/imperative/reducer.cu

+// Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "paddle/fluid/imperative/reducer.h"
+
+namespace paddle {
+namespace imperative {
+
+#if defined(PADDLE_WITH_NCCL)
+void Group::DivNRanks(framework::Tensor *tensor, int64_t nranks,
+                      const platform::DeviceContext &context) {
+  framework::VisitDataTypeSmall(
+      dtype_, DivNRanksForAllReduce<platform::CUDADeviceContext>(tensor, nranks,
+                                                                 context));
+}
+#endif
+
+}  // namespace imperative
+}  // namespace paddle

paddle/fluid/imperative/reducer.h

@@ -29,10 +29,12 @@
 #include "paddle/fluid/framework/tensor.h"
 #include "paddle/fluid/framework/variable.h"
 #include "paddle/fluid/operators/math/math_function.h"
+#include "paddle/fluid/platform/for_range.h"
 
 namespace paddle {
 namespace platform {
 class DeviceContext;
+
 }  // namespace platform
 
 namespace imperative {
@@ -46,6 +48,37 @@ namespace paddle {
 namespace imperative {
 
 #if (defined PADDLE_WITH_NCCL) || (defined PADDLE_WITH_XPU_BKCL)
+
+template <typename T>
+struct DivNRanksFunctor {
+  DivNRanksFunctor(int64_t nranks, T* output)
+      : nranks_(nranks), output_(output) {}
+  HOSTDEVICE void operator()(size_t idx) const {
+    output_[idx] /= static_cast<T>(nranks_);
+  }
+  int64_t nranks_;
+  T* output_;
+};
+
+template <typename Dex>
+struct DivNRanksForAllReduce {
+  framework::Tensor* in_;
+  int64_t nranks_;
+  const platform::DeviceContext& ctx_;
+  DivNRanksForAllReduce(framework::Tensor* in, int64_t nranks,
+                        const platform::DeviceContext& ctx)
+      : in_(in), nranks_(nranks), ctx_(ctx) {}
+
+  template <typename T>
+  void apply() const {
+    T* data = in_->mutable_data<T>(ctx_.GetPlace());
+    platform::ForRange<Dex> for_range(static_cast<const Dex&>(ctx_),
+                                      static_cast<size_t>(in_->numel()));
+    DivNRanksFunctor<T> functor(nranks_, data);
+    for_range(functor);
+  }
+};
+
 class Group {
  public:
   // Here, we use dense_contents_ & sparse_contents_ to
@@ -77,6 +110,12 @@ class Group {
   // context is used to select the stream for split
   void SplitTensors(const platform::DeviceContext& context);
 
+  // use it in CUDA
+  void DivNRanks(framework::Tensor* tensor, int64_t nranks,
+                 const platform::DeviceContext& context);
+
+  void DivNRanks(const platform::DeviceContext& context, int64_t nranks);
+
   friend std::ostream& operator<<(std::ostream&, const Group&);
 };
 
@@ -122,7 +161,6 @@ class Reducer {
  private:
   std::vector<std::shared_ptr<imperative::VarBase>> vars_;
   std::vector<std::vector<size_t>> group_indices_;
-  static std::shared_ptr<Reducer> s_instance_;
   std::vector<Group> groups_;
   size_t next_group_ = 0;
   platform::Place place_;
@@ -132,6 +170,7 @@ class Reducer {
   std::vector<VariableLocator> variable_locators_;
 
   int nrings_ = 1;
+  int64_t nranks_ = -1;
 
   // Following variables are to help rebuild group
   // TODO(shenliang03): Support rebuild in the future.

paddle/fluid/imperative/tests/test_group.cc

@@ -99,6 +99,8 @@ void GroupConcatSplit(Place place, size_t size) {
         .mutable_data(place, group.dtype_);
     group.ConcatTensors(*dev_ctx);
 
+    group.DivNRanks(*dev_ctx, 1);
+
     framework::Tensor tmp;
     framework::TensorCopySync(*tensor, cpu_place, &tmp);
     auto* data = tmp.data<T>();

python/paddle/fluid/dygraph/parallel.py

@@ -308,6 +308,7 @@ def _split_tensors(coalesced_grads_and_grad_vars):
 
 
 def scale_loss(loss):
+    # TODO(liuyuhui) Currently only for xpu. Will be removed in the future.
     if not ParallelEnv().world_size > 1:
         return loss
 

python/paddle/fluid/dygraph/varbase_patch_methods.py

@@ -170,7 +170,8 @@ def monkey_patch_varbase():
 
         """
         if framework.in_dygraph_mode():
-            if paddle.distributed.get_world_size() > 1:
+            if paddle.is_compiled_with_xpu():
+                # TODO(liuyuhui): Currently only for xpu. Will be removed in the future.
                 scaled_loss = scale_loss(self)
                 scaled_loss._run_backward(framework._dygraph_tracer(),
                                           retain_graph)

python/paddle/fluid/tests/unittests/test_dist_base.py

@@ -519,7 +519,8 @@ class TestParallelDyGraphRunnerBase(object):
                 loss.backward()
 
                 opt.minimize(loss)
-                model.clear_gradients()
+                if not args.accumulate_gradient:
+                    model.clear_gradients()
         print_to_out(out_losses)
 
     def run_trainer_with_spawn(self, args):
@@ -594,7 +595,8 @@ class TestParallelDyGraphRunnerBase(object):
             loss.backward()
 
             opt.step()
-            opt.clear_grad()
+            if not args.accumulate_gradient:
+                opt.clear_grad()
         print_to_out(out_losses)
 
 
@@ -625,6 +627,7 @@ def runtime_main(test_class):
     parser.add_argument('--use_cuda', action='store_true')
     parser.add_argument('--use_xpu', action='store_true')
     parser.add_argument('--use_dgc', action='store_true')
+    parser.add_argument('--accumulate_gradient', action='store_true')
     parser.add_argument('--use_reduce', action='store_true')
     parser.add_argument('--dc_asgd', action='store_true')
     parser.add_argument('--hogwild', action='store_true')
@@ -722,6 +725,7 @@ class TestDistBase(unittest.TestCase):
         self._use_hallreduce = False
         self._save_model = False
         self._fuse_all_reduce = None
+        self._accumulate_gradient = False
         self._setup_config()
 
         global DIST_UT_PORT
@@ -845,6 +849,9 @@ class TestDistBase(unittest.TestCase):
         if len(devices) > 1 and self._use_dgc:
             cmd += " --use_dgc"
 
+        if self._accumulate_gradient:
+            cmd += " --accumulate_gradient"
+
         env_local.update(envs)
         print("local_cmd: {}, env: {}".format(cmd, env_local))
 
@@ -1011,6 +1018,9 @@ class TestDistBase(unittest.TestCase):
         if self._use_dgc:
             tr_cmd += " --use_dgc"
 
+        if self._accumulate_gradient:
+            tr_cmd += " --accumulate_gradient"
+
         if self._pipeline_mode:
             tr_cmd += " --use_pipeline"
         if self._mp_mode:

python/paddle/fluid/tests/unittests/test_fleet_base_single.py

@@ -60,7 +60,6 @@ class TestFleetDygraphSingle(unittest.TestCase):
             outputs = dp_layer(inputs)
             labels = paddle.randn([10, 1], 'float32')
             loss = loss_fn(outputs, labels)
-            loss = dp_layer.scale_loss(loss)
             loss.backward()
             adam.step()
             adam.clear_grad()

python/paddle/fluid/tests/unittests/test_parallel_dygraph_mnist.py

@@ -66,12 +66,13 @@ class TestParallelDygraphMnistSpawn(TestDistSpawnRunner):
             self.check_dist_result_with_spawn(test_class=TestMnist, delta=1e-5)
 
 
-class TestFleetDygraphMnist(TestDistBase):
+class TestParallelDygraphMnistAccGrad(TestDistBase):
     def _setup_config(self):
         self._sync_mode = False
         self._nccl2_mode = True
         self._dygraph = True
         self._use_fleet_api = True
+        self._accumulate_gradient = True
 
     def test_mnist(self):
         if fluid.core.is_compiled_with_cuda():

python/paddle/fluid/tests/unittests/test_parallel_dygraph_transformer.py

@@ -48,5 +48,21 @@ class TestParallelDygraphTransformerSpawn(TestDistSpawnRunner):
                 test_class=TestTransformer, delta=1e-5)
 
 
+class TestParallelDygraphTransformerAccGrad(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._nccl2_mode = True
+        self._dygraph = True
+        self._accumulate_gradient = True
+
+    def test_transformer(self):
+        if fluid.core.is_compiled_with_cuda():
+            self.check_with_place(
+                "parallel_dygraph_transformer.py",
+                delta=1e-5,
+                check_error_log=True,
+                log_name=flag_name)
+
+
 if __name__ == "__main__":
     unittest.main()