[CI] Nightly scikit-learn tree node dtype breaks RandomForest and IsolationForest conversions

[csadorf]

Summary

Nightly-dependency wheel tests report 19 tree reconstruction failures while converting cuML RandomForest and IsolationForest models to scikit-learn estimators. The same node dtype mismatch appears in 15 main tests and 4 cuml.accel integration or ONNX tests.

Failing test/component: RandomForest and IsolationForest scikit-learn conversion

Failure observed in:

• https://github.com/NVIDIA/cuml/actions/runs/33482121934
• https://github.com/NVIDIA/cuml/actions/runs/33482121934/job/99773897026

Environment

• OS: Ubuntu 26.04, amd64
• Python version: 3.14.7
• CUDA version: 13.3.0
• GPU: RTX PRO 6000
• Dependencies: nightly-deps; scikit-learn==1.10.dev0, treelite==4.7.1, cuml-cu13==26.10.0a88.post260831062823

Test Details

• Test files:
  • python/cuml/cuml/tests/test_sklearn_import_export.py (5 failures)
  • python/cuml/cuml/tests/test_isolation_forest.py (10 failures)
  • python/cuml/cuml_accel_tests/integration/test_rf_classifier.py (1 failure)
  • python/cuml/cuml_accel_tests/integration/test_rf_regressor.py (1 failure)
  • python/cuml/cuml_accel_tests/test_onnx.py (2 failures)
• Representative tests:
  • test_random_forest_classifier[False]
  • test_as_sklearn_scoring_parity[params0]
  • test_oob_score
  • test_onnx_classifier[RandomForestClassifier]
• Error message:

  ValueError: node array from the pickle has an incompatible dtype:
  - expected: {'names': ['left_child', 'right_child', 'feature', 'threshold', 'left_cat_bitset', 'impurity', 'n_node_samples', 'weighted_n_node_samples', 'missing_go_to_left', 'split_kind'], 'formats': ['<i8', '<i8', '<i8', '<f8', ('<u4', (8,)), '<f8', '<i8', '<f8', 'u1', 'i1'], 'offsets': [0, 8, 16, 24, 32, 64, 72, 80, 88, 89], 'itemsize': 96, 'aligned': True}
  - got     : {'names': ['left_child', 'right_child', 'feature', 'threshold', 'left_cat_bitset', 'impurity', 'n_node_samples', 'weighted_n_node_samples', 'missing_go_to_left'], 'formats': ['<i8', '<i8', '<i8', '<f8', ('<u4', (8,)), '<f8', '<i8', '<f8', 'u1'], 'offsets': [0, 8, 16, 24, 32, 64, 72, 80, 88], 'itemsize': 96, 'aligned': True}
  

Root Cause Analysis

[chyunsu3]

Fix is available in dmlc/treelite#698