Save model in ubj as the default.

jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostClassifierSuite.scala

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014-2022 by Contributors
+ Copyright (c) 2014-2024 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -432,28 +432,29 @@ class XGBoostClassifierSuite extends AnyFunSuite with PerTest with TmpFolderPerS
     val xgb = new XGBoostClassifier(paramMap)
     val model = xgb.fit(trainingDF)
 
+    // test json
     val modelPath = new File(tempDir.toFile, "xgbc").getPath
     model.write.option("format", "json").save(modelPath)
     val nativeJsonModelPath = new File(tempDir.toFile, "nativeModel.json").getPath
     model.nativeBooster.saveModel(nativeJsonModelPath)
     assert(compareTwoFiles(new File(modelPath, "data/XGBoostClassificationModel").getPath,
       nativeJsonModelPath))
 
-    // test default "deprecated"
+    // test ubj
     val modelUbjPath = new File(tempDir.toFile, "xgbcUbj").getPath
     model.write.save(modelUbjPath)
-    val nativeDeprecatedModelPath = new File(tempDir.toFile, "nativeModel").getPath
-    model.nativeBooster.saveModel(nativeDeprecatedModelPath)
+    val nativeUbjModelPath = new File(tempDir.toFile, "nativeModel.ubj").getPath
+    model.nativeBooster.saveModel(nativeUbjModelPath)
     assert(compareTwoFiles(new File(modelUbjPath, "data/XGBoostClassificationModel").getPath,
-      nativeDeprecatedModelPath))
+      nativeUbjModelPath))
 
     // json file should be indifferent with ubj file
     val modelJsonPath = new File(tempDir.toFile, "xgbcJson").getPath
     model.write.option("format", "json").save(modelJsonPath)
-    val nativeUbjModelPath = new File(tempDir.toFile, "nativeModel1.ubj").getPath
-    model.nativeBooster.saveModel(nativeUbjModelPath)
+    val nativeUbjModelPath1 = new File(tempDir.toFile, "nativeModel1.ubj").getPath
+    model.nativeBooster.saveModel(nativeUbjModelPath1)
     assert(!compareTwoFiles(new File(modelJsonPath, "data/XGBoostClassificationModel").getPath,
-      nativeUbjModelPath))
+      nativeUbjModelPath1))
   }
 
   test("native json model file should store feature_name and feature_type") {

jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostRegressorSuite.scala

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014-2022 by Contributors
+ Copyright (c) 2014-2024 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -333,21 +333,24 @@ class XGBoostRegressorSuite extends AnyFunSuite with PerTest with TmpFolderPerSu
     assert(compareTwoFiles(new File(modelPath, "data/XGBoostRegressionModel").getPath,
       nativeJsonModelPath))
 
-    // test default "deprecated"
+    // test default "ubj"
     val modelUbjPath = new File(tempDir.toFile, "xgbcUbj").getPath
     model.write.save(modelUbjPath)
-    val nativeDeprecatedModelPath = new File(tempDir.toFile, "nativeModel").getPath
-    model.nativeBooster.saveModel(nativeDeprecatedModelPath)
-    assert(compareTwoFiles(new File(modelUbjPath, "data/XGBoostRegressionModel").getPath,
-      nativeDeprecatedModelPath))
 
-    // json file should be indifferent with ubj file
-    val modelJsonPath = new File(tempDir.toFile, "xgbcJson").getPath
-    model.write.option("format", "json").save(modelJsonPath)
-    val nativeUbjModelPath = new File(tempDir.toFile, "nativeModel1.ubj").getPath
+    val nativeUbjModelPath = new File(tempDir.toFile, "nativeModel.ubj").getPath
     model.nativeBooster.saveModel(nativeUbjModelPath)
-    assert(!compareTwoFiles(new File(modelJsonPath, "data/XGBoostRegressionModel").getPath,
+
+    assert(compareTwoFiles(new File(modelUbjPath, "data/XGBoostRegressionModel").getPath,
       nativeUbjModelPath))
-  }
 
+    // test the deprecated format
+    val modelDeprecatedPath = new File(tempDir.toFile, "modelDeprecated").getPath
+    model.write.option("format", "deprecated").save(modelDeprecatedPath)
+
+    val nativeDeprecatedModelPath = new File(tempDir.toFile, "nativeModel.deprecated").getPath
+    model.nativeBooster.saveModel(nativeDeprecatedModelPath)
+
+    assert(compareTwoFiles(new File(modelDeprecatedPath, "data/XGBoostRegressionModel").getPath,
+      nativeDeprecatedModelPath))
+  }
 }

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java

@@ -34,7 +34,7 @@
  * Booster for xgboost, this is a model API that support interactive build of a XGBoost Model
  */
 public class Booster implements Serializable, KryoSerializable {
-  public static final String DEFAULT_FORMAT = "deprecated";
+  public static final String DEFAULT_FORMAT = "ubj";
   private static final Log logger = LogFactory.getLog(Booster.class);
   // handle to the booster.
   private long handle = 0;
@@ -788,8 +788,7 @@ private Map<String, Double> getFeatureImportanceFromModel(
   }
 
   /**
-   * Save model into raw byte array. Currently it's using the deprecated format as
-   * default, which will be changed into `ubj` in future releases.
+   * Save model into raw byte array in the UBJSON ("ubj") format.
    *
    * @return the saved byte array
    * @throws XGBoostError native error

jvm-packages/xgboost4j/src/main/scala/ml/dmlc/xgboost4j/scala/Booster.scala

@@ -337,8 +337,7 @@ class Booster private[xgboost4j](private[xgboost4j] var booster: JBooster)
   }
 
   /**
-    * Save model into a raw byte array. Currently it's using the deprecated format as
-   *  default, which will be changed into `ubj` in future releases.
+    * Save model into a raw byte array in the UBJSON ("ubj") format.
     */
   @throws(classOf[XGBoostError])
   def toByteArray: Array[Byte] = {

python-package/xgboost/core.py

@@ -2613,7 +2613,7 @@ def save_model(self, fname: Union[str, os.PathLike]) -> None:
         else:
             raise TypeError("fname must be a string or os PathLike")
 
-    def save_raw(self, raw_format: str = "deprecated") -> bytearray:
+    def save_raw(self, raw_format: str = "ubj") -> bytearray:
         """Save the model to a in memory buffer representation instead of file.
 
         Parameters

python-package/xgboost/testing/__init__.py

@@ -630,7 +630,7 @@ def random_csc(t_id: int) -> sparse.csc_matrix:
 
 def make_datasets_with_margin(
     unweighted_strategy: strategies.SearchStrategy,
-) -> Callable:
+) -> Callable[[], strategies.SearchStrategy[TestDataset]]:
     """Factory function for creating strategies that generates datasets with weight and
     base margin.
 
@@ -668,8 +668,7 @@ def weight_margin(draw: Callable) -> TestDataset:
 
 # A strategy for drawing from a set of example datasets. May add random weights to the
 # dataset
-@memory.cache
-def make_dataset_strategy() -> Callable:
+def make_dataset_strategy() -> strategies.SearchStrategy[TestDataset]:
     _unweighted_datasets_strategy = strategies.sampled_from(
         [
             TestDataset(

src/c_api/c_api.cc

@@ -1313,10 +1313,8 @@ XGB_DLL int XGBoosterLoadModel(BoosterHandle handle, const char* fname) {
 
 namespace {
 void WarnOldModel() {
-  if (XGBOOST_VER_MAJOR >= 2) {
-    LOG(WARNING) << "Saving into deprecated binary model format, please consider using `json` or "
-                    "`ubj`. Model format will default to JSON in XGBoost 2.2 if not specified.";
-  }
+  LOG(WARNING) << "Saving into deprecated binary model format, please consider using `json` or "
+                  "`ubj`. Model format is default to UBJSON in XGBoost 2.1 if not specified.";
 }
 }  // anonymous namespace
 
@@ -1339,14 +1337,14 @@ XGB_DLL int XGBoosterSaveModel(BoosterHandle handle, const char *fname) {
     save_json(std::ios::out);
   } else if (common::FileExtension(fname) == "ubj") {
     save_json(std::ios::binary);
-  } else if (XGBOOST_VER_MAJOR == 2 && XGBOOST_VER_MINOR >= 2) {
-    LOG(WARNING) << "Saving model to JSON as default.  You can use file extension `json`, `ubj` or "
-                    "`deprecated` to choose between formats.";
-    save_json(std::ios::out);
-  } else {
+  } else if (common::FileExtension(fname) == "deprecated") {
     WarnOldModel();
     auto *bst = static_cast<Learner *>(handle);
     bst->SaveModel(fo.get());
+  } else {
+    LOG(WARNING) << "Saving model in the UBJSON format as default.  You can use file extension:"
+                    " `json`, `ubj` or `deprecated` to choose between formats.";
+    save_json(std::ios::binary);
   }
   API_END();
 }

tests/ci_build/lint_python.py

@@ -27,6 +27,7 @@ class LintersPaths:
         "tests/python/test_quantile_dmatrix.py",
         "tests/python/test_tree_regularization.py",
         "tests/python/test_shap.py",
+        "tests/python/test_model_io.py",
         "tests/python/test_with_pandas.py",
         "tests/python-gpu/",
         "tests/python-sycl/",
@@ -83,6 +84,7 @@ class LintersPaths:
         "tests/python/test_multi_target.py",
         "tests/python-gpu/test_gpu_data_iterator.py",
         "tests/python-gpu/load_pickle.py",
+        "tests/python/test_model_io.py",
         "tests/test_distributed/test_with_spark/test_data.py",
         "tests/test_distributed/test_gpu_with_spark/test_data.py",
         "tests/test_distributed/test_gpu_with_dask/test_gpu_with_dask.py",