Fixed bug when num_iterations > early_stopping_round (#50)

src/boosting/gbdt.cpp

@@ -217,9 +217,9 @@ void GBDT::Train() {
     }
   }
   // close file
-  if (early_stopping_round_ > 0) {
-      // save remaining models
-      for (int iter = gbdt_config_->num_iterations - early_stopping_round_; iter < static_cast<int>(models_.size()); ++iter){
+  int remaining_models = gbdt_config_->num_iterations - early_stopping_round_;
+  if (early_stopping_round_ > 0 && remaining_models > 0) {
+      for (int iter = remaining_models; iter < static_cast<int>(models_.size()); ++iter){
         fprintf(output_model_file, "Tree=%d\n", iter);
         fprintf(output_model_file, "%s\n", models_.at(iter)->ToString().c_str());
       }