warning for init_score in save_binary (#2649)

* warning for init_score in save_binary

fix #2639

* Update metadata.cpp

* added info into docs
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

R-package/R/lgb.Dataset.R

@@ -1109,6 +1109,9 @@ lgb.Dataset.set.reference <- function(dataset, reference) {
 
 #' Save \code{lgb.Dataset} to a binary file
 #'
+#' Please note that \code{init_score} is not saved in binary file.
+#' If you need it, please set it again after loading Dataset.
+#'
 #' @param dataset object of class \code{lgb.Dataset}
 #' @param fname object filename of output file
 #'

R-package/man/lgb.Dataset.save.Rd

@@ -15,7 +15,8 @@ lgb.Dataset.save(dataset, fname)
 passed dataset
 }
 \description{
-Save \code{lgb.Dataset} to a binary file
+Please note that \code{init_score} is not saved in binary file.
+If you need it, please set it again after loading Dataset.
 }
 \examples{
 library(lightgbm)

docs/Parameters.rst

@@ -593,6 +593,8 @@ IO Parameters
 
    -  if ``true``, LightGBM will save the dataset (including validation data) to a binary file. This speed ups the data loading for the next time
 
+   -  **Note**: ``init_score`` is not saved in binary file
+
    -  **Note**: can be used only in CLI version; for language-specific packages you can use the correspondent function
 
 -  ``header`` :raw-html:`<a id="header" title="Permalink to this parameter" href="#header">&#x1F517;&#xFE0E;</a>`, default = ``false``, type = bool, aliases: ``has_header``

include/LightGBM/config.h

@@ -563,6 +563,7 @@ struct Config {
 
   // alias = is_save_binary, is_save_binary_file
   // desc = if ``true``, LightGBM will save the dataset (including validation data) to a binary file. This speed ups the data loading for the next time
+  // desc = **Note**: ``init_score`` is not saved in binary file
   // desc = **Note**: can be used only in CLI version; for language-specific packages you can use the correspondent function
   bool save_binary = false;
 

python-package/lightgbm/basic.py

@@ -1149,6 +1149,11 @@ class Dataset(object):
     def save_binary(self, filename):
         """Save Dataset to a binary file.
 
+        .. note::
+
+            Please note that `init_score` is not saved in binary file.
+            If you need it, please set it again after loading Dataset.
+
         Parameters
         ----------
         filename : string

src/io/metadata.cpp

@@ -514,6 +514,10 @@ void Metadata::SaveBinaryToFile(const VirtualFileWriter* writer) const {
   if (!query_boundaries_.empty()) {
     writer->Write(query_boundaries_.data(), sizeof(data_size_t) * (num_queries_ + 1));
   }
+  if (num_init_score_ > 0) {
+    Log::Warning("Please note that `init_score` is not saved in binary file.\n"
+      "If you need it, please set it again after loading Dataset.");
+  }
 }
 
 size_t Metadata::SizesInByte() const {