fix `output_freq` alias.

include/LightGBM/config.h

@@ -444,6 +444,7 @@ struct ParameterAlias {
       { "workers", "machines" },
       { "nodes", "machines" },
       { "subsample_for_bin", "bin_construct_sample_cnt" },
+      { "metric_freq", "output_freq" }
     });
     const std::unordered_set<std::string> parameter_set({
       "config", "config_file", "task", "device",

src/io/config.cpp

@@ -422,7 +422,7 @@ void BoostingConfig::Set(const std::unordered_map<std::string, std::string>& par
   CHECK(learning_rate > 0.0f);
   GetInt(params, "early_stopping_round", &early_stopping_round);
   CHECK(early_stopping_round >= 0);
-  GetInt(params, "metric_freq", &output_freq);
+  GetInt(params, "output_freq", &output_freq);
   CHECK(output_freq >= 0);
   GetBool(params, "is_training_metric", &is_provide_training_metric);
   GetInt(params, "num_class", &num_class);