fix sycn training error (#31357)

* fix sycn training error

Change-Id: Ie2feebcf0b5b2984fd59cfcdde0c817840e203d2

paddle/fluid/distributed/table/common_dense_table.cc

@@ -120,6 +120,7 @@ int32_t CommonDenseTable::push_dense_param(const float* values, size_t num) {
 }
 
 int32_t CommonDenseTable::pour() {
+  pull_reservoir_.avg();
   _push_dense(pull_reservoir_.values.data(), pull_reservoir_.values.size());
   pull_reservoir_.reset();
   return 0;

paddle/fluid/distributed/table/common_table.h

@@ -55,12 +55,13 @@ struct ReservoirValue {
   }
 
   void avg() {
+    if (counter == 0) return;
     auto scale = 1 / static_cast<T>(counter);
     GetBlas<T>().SCAL(values.size(), scale, values.data());
   }
 
   void reset() {
-    values.resize(dim, 0);
+    std::fill(values.begin(), values.end(), 0);
     counter = 0;
   }
 };
@@ -134,15 +135,15 @@ class BarrierTable : public Table {
     return 0;
   }
   int32_t shrink(const std::string &param) override { return 0; }
-  virtual void clear(){};
-  virtual int32_t flush() { return 0; };
+  virtual void clear() {}
+  virtual int32_t flush() { return 0; }
   virtual int32_t load(const std::string &path, const std::string &param) {
     return 0;
   }
   virtual int32_t save(const std::string &path, const std::string &param) {
     return 0;
   }
-  virtual int32_t initialize_shard() { return 0; };
+  virtual int32_t initialize_shard() { return 0; }
 
   virtual int32_t initialize() override;
   // only for barrier