change unit size to MB.

include/LightGBM/config.h

@@ -140,7 +140,7 @@ public:
   int num_leaves = 127;
   int feature_fraction_seed = 2;
   double feature_fraction = 1.0;
-  // max cache size(unit:GB) for historical histogram. < 0 means not limit
+  // max cache size(unit:MB) for historical histogram. < 0 means not limit
   double histogram_pool_size = -1;
   void Set(const std::unordered_map<std::string, std::string>& params) override;
 };

src/io/config.cpp

@@ -130,7 +130,7 @@ void OverallConfig::CheckParamConflict() {
     is_parallel_find_bin = true;
     if (gbdt_config->tree_config.histogram_pool_size >= 0) {
       Log::Error("Histogram LRU queue was enabled (histogram_pool_size=%f). Will disable this for reducing communication cost."
-                 , tree_config.histogram_pool_size);
+                 , gbdt_config->tree_config.histogram_pool_size);
       // Change pool size to -1(not limit) when using data parallel for reducing communication cost
       gbdt_config->tree_config.histogram_pool_size = -1;
     }

src/treelearner/serial_tree_learner.cpp

@@ -55,8 +55,7 @@ void SerialTreeLearner::Init(const Dataset* train_data) {
     for (int i = 0; i < train_data_->num_features(); ++i) {
       total_histogram_size += sizeof(HistogramBinEntry) * train_data_->FeatureAt(i)->num_bin();
     }
-    max_cache_size = static_cast<int>(histogram_pool_size_ * 1024 * 1024 * 1024 / total_histogram_size);
-    
+    max_cache_size = static_cast<int>(histogram_pool_size_ * 1024 * 1024 / total_histogram_size);
   }
   // at least need 2 leaves
   max_cache_size = Common::Max(2, max_cache_size);