|
| 1 | +# Multi Chain Demo Script |
| 2 | + |
| 3 | +# Load necessary libraries |
| 4 | +from multiprocessing import Pool, cpu_count |
| 5 | + |
| 6 | +import matplotlib.pyplot as plt |
| 7 | +import numpy as np |
| 8 | +import pandas as pd |
| 9 | +import seaborn as sns |
| 10 | +from sklearn.model_selection import train_test_split |
| 11 | + |
| 12 | +from stochtree import BARTModel |
| 13 | + |
| 14 | + |
| 15 | +def fit_bart( |
| 16 | + model_string, |
| 17 | + X_train, |
| 18 | + y_train, |
| 19 | + basis_train, |
| 20 | + X_test, |
| 21 | + basis_test, |
| 22 | + num_mcmc, |
| 23 | + gen_param_list, |
| 24 | + mean_list, |
| 25 | + i, |
| 26 | +): |
| 27 | + bart_model = BARTModel() |
| 28 | + bart_model.sample( |
| 29 | + X_train=X_train, |
| 30 | + y_train=y_train, |
| 31 | + leaf_basis_train=basis_train, |
| 32 | + X_test=X_test, |
| 33 | + leaf_basis_test=basis_test, |
| 34 | + num_gfr=0, |
| 35 | + num_mcmc=num_mcmc, |
| 36 | + previous_model_json=model_string, |
| 37 | + previous_model_warmstart_sample_num=i, |
| 38 | + general_params=gen_param_list, |
| 39 | + mean_forest_params=mean_list, |
| 40 | + ) |
| 41 | + return (bart_model.to_json(), bart_model.y_hat_test) |
| 42 | + |
| 43 | + |
| 44 | +def bart_warmstart_parallel(X_train, y_train, basis_train, X_test, basis_test): |
| 45 | + # Run the GFR algorithm for a small number of iterations |
| 46 | + general_model_params = {"random_seed": -1} |
| 47 | + mean_forest_model_params = {"num_trees": 100} |
| 48 | + num_warmstart = 10 |
| 49 | + num_mcmc = 100 |
| 50 | + bart_model = BARTModel() |
| 51 | + bart_model.sample( |
| 52 | + X_train=X_train, |
| 53 | + y_train=y_train, |
| 54 | + leaf_basis_train=basis_train, |
| 55 | + X_test=X_test, |
| 56 | + leaf_basis_test=basis_test, |
| 57 | + num_gfr=num_warmstart, |
| 58 | + num_mcmc=0, |
| 59 | + general_params=general_model_params, |
| 60 | + mean_forest_params=mean_forest_model_params, |
| 61 | + ) |
| 62 | + bart_model_json = bart_model.to_json() |
| 63 | + |
| 64 | + # Warm-start multiple BART fits from a different GFR forest |
| 65 | + process_tasks = [ |
| 66 | + ( |
| 67 | + bart_model_json, |
| 68 | + X_train, |
| 69 | + y_train, |
| 70 | + basis_train, |
| 71 | + X_test, |
| 72 | + basis_test, |
| 73 | + num_mcmc, |
| 74 | + general_model_params, |
| 75 | + mean_forest_model_params, |
| 76 | + i, |
| 77 | + ) |
| 78 | + for i in range(4) |
| 79 | + ] |
| 80 | + num_processes = cpu_count() |
| 81 | + with Pool(processes=num_processes) as pool: |
| 82 | + results = pool.starmap(fit_bart, process_tasks) |
| 83 | + |
| 84 | + # Extract separate outputs as separate lists |
| 85 | + bart_model_json_list, bart_model_pred_list = zip(*results) |
| 86 | + |
| 87 | + # Process results |
| 88 | + combined_bart_model = BARTModel() |
| 89 | + combined_bart_model.from_json_string_list(bart_model_json_list) |
| 90 | + combined_bart_preds = bart_model_pred_list[0] |
| 91 | + for i in range(1, len(bart_model_pred_list)): |
| 92 | + combined_bart_preds = np.concatenate( |
| 93 | + (combined_bart_preds, bart_model_pred_list[i]), axis=1 |
| 94 | + ) |
| 95 | + |
| 96 | + return (combined_bart_model, combined_bart_preds) |
| 97 | + |
| 98 | + |
| 99 | +if __name__ == "__main__": |
| 100 | + # RNG |
| 101 | + random_seed = 1234 |
| 102 | + rng = np.random.default_rng(random_seed) |
| 103 | + |
| 104 | + # Generate covariates and basis |
| 105 | + n = 1000 |
| 106 | + p_X = 10 |
| 107 | + p_W = 1 |
| 108 | + X = rng.uniform(0, 1, (n, p_X)) |
| 109 | + W = rng.uniform(0, 1, (n, p_W)) |
| 110 | + |
| 111 | + # Define the outcome mean function |
| 112 | + def outcome_mean(X, W): |
| 113 | + return np.where( |
| 114 | + (X[:, 0] >= 0.0) & (X[:, 0] < 0.25), |
| 115 | + -7.5 * W[:, 0], |
| 116 | + np.where( |
| 117 | + (X[:, 0] >= 0.25) & (X[:, 0] < 0.5), |
| 118 | + -2.5 * W[:, 0], |
| 119 | + np.where( |
| 120 | + (X[:, 0] >= 0.5) & (X[:, 0] < 0.75), 2.5 * W[:, 0], 7.5 * W[:, 0] |
| 121 | + ), |
| 122 | + ), |
| 123 | + ) |
| 124 | + |
| 125 | + # Generate outcome |
| 126 | + f_XW = outcome_mean(X, W) |
| 127 | + epsilon = rng.normal(0, 1, n) |
| 128 | + y = f_XW + epsilon |
| 129 | + |
| 130 | + # Test-train split |
| 131 | + sample_inds = np.arange(n) |
| 132 | + train_inds, test_inds = train_test_split( |
| 133 | + sample_inds, test_size=0.2, random_state=random_seed |
| 134 | + ) |
| 135 | + X_train = X[train_inds, :] |
| 136 | + X_test = X[test_inds, :] |
| 137 | + basis_train = W[train_inds, :] |
| 138 | + basis_test = W[test_inds, :] |
| 139 | + y_train = y[train_inds] |
| 140 | + y_test = y[test_inds] |
| 141 | + |
| 142 | + # Run the parallel BART |
| 143 | + combined_bart, combined_bart_preds = bart_warmstart_parallel( |
| 144 | + X_train, y_train, basis_train, X_test, basis_test |
| 145 | + ) |
| 146 | + |
| 147 | + # Inspect the model outputs |
| 148 | + y_hat_mcmc = combined_bart.predict(X_test, basis_test) |
| 149 | + y_avg_mcmc = np.squeeze(y_hat_mcmc).mean(axis=1, keepdims=True) |
| 150 | + y_df = pd.DataFrame( |
| 151 | + np.concatenate((y_avg_mcmc, np.expand_dims(y_test, axis=1)), axis=1), |
| 152 | + columns=["Average BART Predictions", "Outcome"], |
| 153 | + ) |
| 154 | + |
| 155 | + # Compare first warm-start chain to outcome |
| 156 | + sns.scatterplot(data=y_df, x="Average BART Predictions", y="Outcome") |
| 157 | + plt.axline((0, 0), slope=1, color="black", linestyle=(0, (3, 3))) |
| 158 | + plt.show() |
| 159 | + |
| 160 | + # Compare cached predictions to deserialized predictions for first chain |
| 161 | + chain_index = 0 |
| 162 | + num_mcmc = 100 |
| 163 | + offset_index = num_mcmc * chain_index |
| 164 | + chain_inds = slice(offset_index, (offset_index + num_mcmc)) |
| 165 | + chain_1_preds_original = np.squeeze(combined_bart_preds[chain_inds]).mean( |
| 166 | + axis=1, keepdims=True |
| 167 | + ) |
| 168 | + chain_1_preds_reloaded = np.squeeze(y_hat_mcmc[chain_inds]).mean( |
| 169 | + axis=1, keepdims=True |
| 170 | + ) |
| 171 | + chain_df = pd.DataFrame( |
| 172 | + np.concatenate((chain_1_preds_reloaded, chain_1_preds_original), axis=1), |
| 173 | + columns=["New Predictions", "Original Predictions"], |
| 174 | + ) |
| 175 | + sns.scatterplot(data=chain_df, x="New Predictions", y="Original Predictions") |
| 176 | + plt.axline((0, 0), slope=1, color="black", linestyle=(0, (3, 3))) |
| 177 | + plt.show() |
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