force set to zero to prediction buffer.

src/boosting/gbdt.cpp

@@ -774,6 +774,7 @@ std::string GBDT::ModelToIfElse(int num_iteration) const {
   std::stringstream pred_str_buf;
 
   pred_str_buf << "\t" << "int early_stop_round_counter = 0;" << std::endl;
+  pred_str_buf << "\t" << "std::memset(output, 0, sizeof(double) * num_tree_per_iteration_);" << std::endl;
   pred_str_buf << "\t" << "for (int i = 0; i < num_iteration_for_pred_; ++i) {" << std::endl;
   pred_str_buf << "\t\t" << "for (int k = 0; k < num_tree_per_iteration_; ++k) {" << std::endl;
   pred_str_buf << "\t\t\t" << "output[k] += (*PredictTreePtr[i * num_tree_per_iteration_ + k])(features);" << std::endl;

src/boosting/gbdt_prediction.cpp

@@ -8,12 +8,13 @@ namespace LightGBM {
 
 void GBDT::PredictRaw(const double* features, double* output, const PredictionEarlyStopInstance* early_stop) const {
   int early_stop_round_counter = 0;
+  // set zero
+  std::memset(output, 0, sizeof(double) * num_tree_per_iteration_);
   for (int i = 0; i < num_iteration_for_pred_; ++i) {
     // predict all the trees for one iteration
     for (int k = 0; k < num_tree_per_iteration_; ++k) {
       output[k] += models_[i * num_tree_per_iteration_ + k]->Predict(features);
     }
-
     // check early stopping
     ++early_stop_round_counter;
     if (early_stop->round_period == early_stop_round_counter) {
@@ -27,7 +28,6 @@ void GBDT::PredictRaw(const double* features, double* output, const PredictionEa
 
 void GBDT::Predict(const double* features, double* output, const PredictionEarlyStopInstance* early_stop) const {
   PredictRaw(features, output, early_stop);
-
   if (objective_function_ != nullptr) {
     objective_function_->ConvertOutput(output, output);
   }