Table 2 Hyperparameter search space for each algorithm.

From: Stacked machine learning models for accurate estimation of shear and Stoneley wave transit times in DSI log

Algorithm

Hyperparameters

Search space

RF

n_estimators

max_depth

min_samples_split

min_samples_leaf

max_features

[100, 200, 500]

[10, 20, 30]

[2, 5, 7]

[1,2,4]

[‘auto’, ‘log2’]

GB

learning_rate

min_samples_split

min_samples_leaf

n_estimators

[0.1, 0.01, 0.001]

[10, 20, 30]

[2, 5, 7]

[50, 100]

MPR

Degree

2

SVR

Kernel

C

[‘rbf’]

[5,7,10]

MLR

n_jobs

5

CatBoost

learning_rate

n_estimators

depth

l2_leaf_reg

[0.01, 0.1, 0.2]

[100, 200, 300]

[4, 6, 8]

[1, 3, 5]

LightGBM

boosting_type

num_leaves

max_depth

learning_rate

n_estimators

subsample_for_bin

objective

min_child_weight

min_child_samples subsample

[gbdt]

[31,63]

[6,8,10]

[0.01, 0.05, 0.001]

[50, 100]

[1000, 1500, 2000]

[regression]

[1,5,10]

[20]

ANN

activation

optimizer

loss

epochs

batch_size

[relu]

[adam]

[mean_squared_error]

[50,100,150,200]

[16,32,64]