reduce verbosity of some log messages (#6073)

R-package/tests/testthat/test_basic.R

@@ -3265,6 +3265,8 @@ test_that("lightgbm() accepts 'weight' and 'weights'", {
     , metric =  "auc"
     , early_stopping_round = nrounds
     , num_threads = .LGB_MAX_THREADS
+    # include a nonsense parameter just to trigger a WARN-level log
+    , nonsense_param = 1.0
   )
   if (!is.null(verbose_param)) {
     params[["verbose"]] <- verbose_param

src/c_api.cpp

@@ -150,7 +150,7 @@ class Booster {
     objective_fun_.reset(ObjectiveFunction::CreateObjectiveFunction(config_.objective,
                                                                     config_));
     if (objective_fun_ == nullptr) {
-      Log::Warning("Using self-defined objective function");
+      Log::Info("Using self-defined objective function");
     }
     // initialize the objective function
     if (objective_fun_ != nullptr) {
@@ -320,7 +320,7 @@ class Booster {
       objective_fun_.reset(ObjectiveFunction::CreateObjectiveFunction(config_.objective,
                                                                       config_));
       if (objective_fun_ == nullptr) {
-        Log::Warning("Using self-defined objective function");
+        Log::Info("Using self-defined objective function");
       }
       // initialize the objective function
       if (objective_fun_ != nullptr) {

src/io/dataset.cpp

@@ -699,7 +699,7 @@ TrainingShareStates* Dataset::GetShareStates(
 
     if (col_wise_time < row_wise_time) {
       auto overhead_cost = row_wise_init_time + row_wise_time + col_wise_time;
-      Log::Warning(
+      Log::Info(
           "Auto-choosing col-wise multi-threading, the overhead of testing was "
           "%f seconds.\n"
           "You can set `force_col_wise=true` to remove the overhead.",
@@ -707,7 +707,7 @@ TrainingShareStates* Dataset::GetShareStates(
       return col_wise_state.release();
     } else {
       auto overhead_cost = col_wise_init_time + row_wise_time + col_wise_time;
-      Log::Warning(
+      Log::Info(
           "Auto-choosing row-wise multi-threading, the overhead of testing was "
           "%f seconds.\n"
           "You can set `force_row_wise=true` to remove the overhead.\n"