refine comment and code

Author: tensor-tang

paddle/gserver/layers/MKLDNNBatchNormLayer.cpp

@@ -109,19 +109,10 @@ void MKLDNNBatchNormLayer::convertWeightsFromPaddle() {
 void MKLDNNBatchNormLayer::calMovingMeanAndVar() {
   // calculating and saving moving mean and variance
   CHECK_EQ(useGlobalStats_, false);
-  MatrixPtr movingMean = movingMean_->getW();
-  MatrixPtr movingVar = movingVar_->getW();
-  if (FLAGS_trainer_count > 1) {
-    auto mvMean = std::dynamic_pointer_cast<SharedCpuMatrix>(movingMean);
-    auto mvVar = std::dynamic_pointer_cast<SharedCpuMatrix>(movingVar);
-    CHECK(mvMean && mvVar);
-    mvMean->add(*mean_, movingAvgFraction_, 1.0 - movingAvgFraction_);
-    mvVar->add(*var_, movingAvgFraction_, 1.0 - movingAvgFraction_);
-  } else {
-    movingMean->add(*mean_, movingAvgFraction_, 1.0 - movingAvgFraction_);
-    // here var is v^2
-    movingVar->add(*var_, movingAvgFraction_, 1.0 - movingAvgFraction_);
-  }
+  movingMean_->getW()->add(
+      *mean_, movingAvgFraction_, 1.0 - movingAvgFraction_);
+  // here var is v^2
+  movingVar_->getW()->add(*var_, movingAvgFraction_, 1.0 - movingAvgFraction_);
 }
 
 void MKLDNNBatchNormLayer::reshape(
@@ -142,8 +133,9 @@ void MKLDNNBatchNormLayer::resetFwd(std::vector<primitive>& pipeline,
                                     MKLDNNMatrixPtr& wgt,
                                     MKLDNNMatrixPtr& bias,
                                     MKLDNNMatrixPtr& out) {
-  // in training always calculate mean and var, so useGlobalStats must be false
-  // in test depends on useGlobalStats
+  // In training phase, it will always calculate mean and var,
+  // so useGlobalStats must be false.
+  // In scoring phase, it depends on useGlobalStats choice.
   if (passType_ != PASS_TEST && useGlobalStats_ == true) {
     LOG(WARNING) << "use_global_stats is invalid setting in training phase";
     useGlobalStats_ = false;
@@ -173,7 +165,7 @@ void MKLDNNBatchNormLayer::resetBwd(std::vector<primitive>& pipeline,
 void MKLDNNBatchNormLayer::forward(PassType passType) {
   MKLDNNLayer::forward(passType);
 
-  // calculating and saving moving mean and variance
+  // calculate and save moving mean and variance
   if (passType_ != PASS_TEST) {
     calMovingMeanAndVar();
   }

paddle/gserver/layers/MKLDNNBatchNormLayer.h

@@ -56,8 +56,10 @@ class MKLDNNBatchNormLayer : public MKLDNNLayer {
   bool hasInitedWgt_;
 
   // local mean and variance
-  MKLDNNMatrixPtr mean_;  // output of mkldnn: m
-  MKLDNNMatrixPtr var_;   // output of mkldnn: v^2
+  // when useGlobalStats_ they are loaded from moving mean and variance
+  // when do not useGlobalStats_ they are calculated from this mini-batch
+  MKLDNNMatrixPtr mean_;
+  MKLDNNMatrixPtr var_;
 
 public:
   explicit MKLDNNBatchNormLayer(const LayerConfig& config)