Solve inconsistent order in each card in dynamic graph (#30931)

paddle/fluid/imperative/reducer.cc

@@ -181,11 +181,6 @@ void SplitTensorsWithType<platform::XPUDeviceContext>(
 #endif
 
 void Group::ConcatTensors(const platform::DeviceContext &context) {
-  VLOG(3) << "Before concat, set output tensor size is " << all_length_;
-  auto tensor = dense_contents_.GetMutable<framework::LoDTensor>();
-  tensor->Resize(framework::make_ddim({all_length_}))
-      .mutable_data(context.GetPlace(), dtype_);
-
   auto place = context.GetPlace();
   if (platform::is_gpu_place(place)) {
 #ifdef PADDLE_WITH_NCCL
@@ -320,6 +315,9 @@ void Reducer::InitializeDenseGroups(
 
     p_group->length_.push_back(size);
 
+    // for concat operator
+    p_group->dense_tensors_.push_back(framework::Tensor());
+
     // check the dtype and place, it must be same.
     auto dtype = var->DataType();
     auto place = var->Place();
@@ -341,6 +339,7 @@ void Reducer::InitializeDenseGroups(
       place_ = place;
     }
   }
+  p_group->all_length_ = all_length;
 }
 
 // Each parameter will be initialized according to the group information.
@@ -375,6 +374,9 @@ void Reducer::InitializeGroups(
     } else {
       // process the dense gradient.
       InitializeDenseGroups(variable_indices_, &group);
+      auto tensor = group.dense_contents_.GetMutable<framework::LoDTensor>();
+      tensor->Resize(framework::make_ddim({group.all_length_}))
+          .mutable_data(place_, group.dtype_);
     }
 
     // map variables to this group by VariableLocator
@@ -436,9 +438,6 @@ void Reducer::PrepareForBackward(
   next_group_ = 0;
   std::for_each(groups_.begin(), groups_.end(), [](Group &group) {
     group.pending_ = group.variable_indices_.size();
-    group.all_length_ = 0;
-    group.dense_tensors_.clear();
-    group.dense_tensors_.reserve(group.pending_);
     group.sparse_contents_ = nullptr;
   });
 
@@ -564,22 +563,42 @@ void Reducer::MarkVarReady(const size_t var_index, const bool is_used_var) {
   auto group_index = var_locator.group_index;
   auto &group = groups_[group_index];
 
-  if (is_used_var) {
-    auto var_warpper = vars_[var_index]->GradVarBase()->SharedVar();
   if (!group.is_sparse_) {
-      auto grad = var_warpper->MutableVar();
+    // process dense group
     auto inside_group_index = var_locator.inside_group_index;
     auto length = group.length_[inside_group_index];
-
-      auto tensor = grad->GetMutable<framework::LoDTensor>();
-      framework::Tensor tmp;
-      tmp.ShareDataWith(*tensor).Resize({static_cast<int64_t>(length)});
-      group.dense_tensors_.push_back(std::move(tmp));
-      group.all_length_ += length;
+    auto &group_tensor = group.dense_tensors_[inside_group_index];
+    if (is_used_var) {
+      auto var_warpper = vars_[var_index]->GradVarBase()->SharedVar();
+      auto tensor =
+          var_warpper->MutableVar()->GetMutable<framework::LoDTensor>();
+      group_tensor.ShareDataWith(*tensor).Resize(
+          {static_cast<int64_t>(length)});
     } else {
+      if (!group_tensor.IsInitialized()) {
+        group_tensor.Resize({static_cast<int64_t>(length)});
+        group_tensor.mutable_data(place_, group.dtype_);
+#ifdef PADDLE_WITH_XPU_BKCL
+        if (platform::is_xpu_place(group_tensor.place())) {
+          // TODO(liuyuhui) support XPU set constant
+          VLOG(3) << "XPU doesn't support set_constant";
+        }
+#else
+        auto *dev_ctx = platform::DeviceContextPool::Instance().Get(place_);
+        operators::math::set_constant(*dev_ctx, &group_tensor, 0.0);
+#endif
+      }
+    }
+  } else {
+    // process sparse group
+    if (is_used_var) {
+      auto var_warpper = vars_[var_index]->GradVarBase()->SharedVar();
       group.sparse_contents_ = var_warpper->MutableVar();
+    } else {
+      group.sparse_contents_ = nullptr;
     }
   }
+
   if (--group.pending_ == 0) {
     // can start allreduce
     MarkGroupReady(group_index);
@@ -619,17 +638,15 @@ void Reducer::MarkGroupReady(size_t group_index) {
                 << "] has no var to allreduce";
       }
     } else {
-      if (!group.dense_tensors_.empty()) {
-        VLOG(3) << "dense group [" << next_group_
-                << "] start allreduce in ring[" << run_order << "]";
+      VLOG(3) << "dense group [" << next_group_ << "] start allreduce in ring["
+              << run_order << "]";
       // Select common commstream to concat tensors
       // group.dense_tensors ---> group.dense_contents_
       group.ConcatTensors(*parallel_ctx_->GetDeviceContext(run_order));
 
 // NOTE(liuyuhui): ConcatTensors use communication stream, but BKCL only support
-// default stream for communicating,
-// so there exist some problems in synchronization. And need to add a WaitComm
-// there.
+// default stream for communicating, so there exist some problems in
+// synchronization. And need to add a WaitComm there.
 // TODO(liuyuhui): If BKCL support events, it should be fixed as non-blocking
 // communication.
 #ifdef PADDLE_WITH_XPU_BKCL
@@ -645,10 +662,6 @@ void Reducer::MarkGroupReady(size_t group_index) {
       // Select common commstream to split tensors
       // group.dense_contents_ ---> group.dense_tensors
       group.SplitTensors(*parallel_ctx_->GetDeviceContext(run_order));
-      } else {
-        VLOG(3) << "The dense group[" << next_group_
-                << "] has no var to allreduce";
-      }
     }
   }
 }

paddle/fluid/imperative/reducer.h

@@ -28,6 +28,7 @@
 #include "paddle/fluid/framework/data_type.h"
 #include "paddle/fluid/framework/tensor.h"
 #include "paddle/fluid/framework/variable.h"
+#include "paddle/fluid/operators/math/math_function.h"
 
 namespace paddle {
 namespace platform {
@@ -133,7 +134,8 @@ class Reducer {
   int nrings_ = 1;
 
   // Following variables are to help rebuild group
-  bool has_rebuilt_group_{false};
+  // TODO(shenliang03): Support rebuild in the future.
+  bool has_rebuilt_group_{true};
   std::vector<std::shared_ptr<imperative::VarBase>> rebuild_vars_;
   std::vector<int64_t> rebuild_var_indices_;
   const std::vector<size_t> group_size_limits_;

paddle/fluid/imperative/tests/test_group.cc

@@ -94,9 +94,11 @@ void GroupConcatSplit(Place place, size_t size) {
   auto* dev_ctx = pool.Get(place);
 
   {  // concat
+    auto* tensor = group.dense_contents_.GetMutable<framework::LoDTensor>();
+    tensor->Resize(framework::make_ddim({group.all_length_}))
+        .mutable_data(place, group.dtype_);
     group.ConcatTensors(*dev_ctx);
 
-    auto* tensor = group.dense_contents_.GetMutable<framework::LoDTensor>();
     framework::Tensor tmp;
     framework::TensorCopySync(*tensor, cpu_place, &tmp);
     auto* data = tmp.data<T>();