# AMD Threadripper PRO 5975WX (Zen 3), Ubuntu 24.04, 8 CPUs (taskset -c 32-39), Python 3.12.3, scikit-learn 1.9.1, numpy 2.5.4, pandas 3.0.6, joblib 1.6.0, 12 October 2026
# official wheel: lightgbm 4.7.0 from PyPI

$ python pi_cost.py count work
predict calls: 251 (1 + 50 features x 5 repeats), 10000 rows each, 300 trees: 753 million tree walks
one predict_proba over 10000 rows, 1 thread(s): 234.4 ms (median of 7)
one predict_proba over 10000 rows, 8 thread(s): 31.5 ms (median of 7)

$ python pi_cost.py all work 3
N = 8 CPUs, 3 rounds per setting, median wall time of the permutation_importance call
pandas, n_jobs=1, 1 thread                          59.57 s   5f242b6b5bd26ee0 same result
numpy, n_jobs=1, 1 thread                           59.23 s   5f242b6b5bd26ee0 same result
numpy, n_jobs=1, N threads                           8.58 s   5f242b6b5bd26ee0 same result
numpy, n_jobs=N, 1 thread                           10.44 s   5f242b6b5bd26ee0 same result
pandas, n_jobs=N, 1 thread                          10.33 s   5f242b6b5bd26ee0 same result
numpy, n_jobs=N, LightGBM default threads           11.64 s   5f242b6b5bd26ee0 same result
numpy, n_jobs=N, 1 thread, max_samples=0.5           6.05 s   b756cc6b72a439bd DIFFERENT result
numpy, n_jobs=N, 1 thread, n_repeats=2               5.25 s   df04964ce9cc6f9e DIFFERENT result
numpy float32, n_jobs=N, 1 thread                   10.32 s   5f242b6b5bd26ee0 same result

$ python pi_cost.py all work 3 "pandas, n_jobs=1, LightGBM default threads" "numpy, n_jobs=2, N/2 threads"
N = 8 CPUs, 3 rounds per setting, median wall time of the permutation_importance call
pandas, n_jobs=1, LightGBM default threads           9.10 s   5f242b6b5bd26ee0 same result
numpy, n_jobs=2, N/2 threads                        10.40 s   5f242b6b5bd26ee0 same result

$ python pi_cost.py prep work30 30; python pi_cost.py all work30 5 ...   (a 30-tree model)
N = 8 CPUs, 5 rounds per setting, median wall time of the permutation_importance call
pandas, n_jobs=1, 1 thread                           4.99 s   c9ac260ed8fc0f53 same result
numpy, n_jobs=1, 1 thread                            4.66 s   c9ac260ed8fc0f53 same result
pandas, n_jobs=1, LightGBM default threads           1.75 s   c9ac260ed8fc0f53 same result
numpy, n_jobs=1, N threads                           1.40 s   c9ac260ed8fc0f53 same result