OpenCV/opencv_contrib/modules/face/samples/sample_config_file.xml

<?xml version="1.0"?>
<!-- cascade_depth stores the depth of cascade of regressors used for training.
     tree_depth    stores the depth of trees created as weak learners during gradient boosting.
     num_trees_per_cascade_level stores number of trees required per cascade level.
     learning_rate stores the learning rate for gradient boosting.This is required to prevent overfitting using shrinkage.
     oversampling_amount stores the oversampling amount for the samples.
     num_test_coordinates stores number of test coordinates to be generated as samples to decide for making the split.
     lambda stores the value used for calculating the probabilty which helps to select closer pixels for making the split.
     num_test_splits stores the number of test splits to be generated before making the best split.
 -->
<opencv_storage>
<cascade_depth>15</cascade_depth>
<tree_depth>4</tree_depth>
<num_trees_per_cascade_level>500</num_trees_per_cascade_level>
<learning_rate>1.0000000149011612e-01</learning_rate>
<oversampling_amount>20</oversampling_amount>
<num_test_coordinates>400</num_test_coordinates>
<lambda>1.0000000149011612e-01</lambda>
<num_test_splits>20</num_test_splits>
</opencv_storage>