待翻譯：Adaptive Experimentation with Meta’s Ax: A Practical Coding Guide

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In this tutorial, we explore adaptive experimentation using Meta’s Ax with the modern Client API. We work through a complete workflow where we tune a RandomForest model on a synthetic classification dataset while balancing predictive accuracy against model footprint. We begin by defining a mixed search space with integer, float, log-scaled, and categorical parameters, then use Ax’s ask-tell optimization loop to run constrained Bayesian optimization, multi-objective optimization, and parameter-constrained experimentation. Along the way, we visualize convergence, inspect the Pareto frontier, use Ax’s built-in analysis tools, and persist the experiment for future reuse. Copy CodeCopiedUse a different Browser import importlib, subprocess, sys def _ensure(module, pip_name=None): try: importlib.import_module(module) except ImportError: print(f"Installing {pip_name or module} ...") subprocess.check_call([sys.executable, "-m", "pip", "install", "-q", pip_name or module]) _ensure("ax", "ax-platform") _ensure("sklearn", "scikit-learn") import logging, warnings, time import numpy as np import matplotlib.pyplot as plt warnings.filterwarnings("ignore") logging.getLogger("ax").setLevel(logging.WARNING) from ax.api.client import Client from ax.api.configs import RangeParameterConfig, ChoiceParameterConfig from sklearn.datasets import make_classification from sklearn.ensemble import RandomForestClassifier from sklearn.model_selection import StratifiedKFold, cross_val_score np.random.seed(0) We begin by preparing the Colab environment and installing the required packages for Ax and scikit-learn. We import the core libraries for optimization, machine learning, plotting, logging, and reproducibility. We also configure warnings and Ax logging to keep the notebook output clean and focused on the experimental results. Copy CodeCopiedUse a different Browser X, y = make_classification( n_samples=1400, n_features=20, n_informative=8, n_redundant=4, n_classes=3, random_state=0, ) CV = StratifiedKFold(n_splits=3, shuffle=True, random_state=0) def evaluate(p): n_est, depth = int(p["n_estimators"]), int(p["max_depth"]) clf = RandomForestClassifier( n_estimators=n_est, max_depth=depth, max_features=float(p["max_features"]), min_samples_leaf=int(p["min_samples_leaf"]), criterion=p["criterion"], ccp_alpha=float(p["ccp_alpha"]), n_jobs=-1, random_state=0, ) accuracy = cross_val_score(clf, X, y, cv=CV, scoring="accuracy").mean() model_size = n_est * depth return {"accuracy": float(accuracy), "model_size": float(model_size)} SEARCH_SPACE = [ RangeParameterConfig(name="n_estimators", bounds=(50, 300), parameter_type="int"), RangeParameterConfig(name="max_depth", bounds=(3, 24), parameter_type="int"), RangeParameterConfig(name="max_features", bounds=(0.2, 1.0), parameter_type="float"), RangeParameterConfig(name="min_samples_leaf",bounds=(1, 12), parameter_type="int"), RangeParameterConfig(name="ccp_alpha", bounds=(1e-5, 1e-1), parameter_type="float", scaling="log"), ChoiceParameterConfig(name="criterion", values=["gini", "entropy", "log_loss"], parameter_type="str", is_ordered=False), ] def run_study(client, total_trials, metric_keys, batch=4): records = [] while len(records) 16}: {v}") print(" predicted:", prediction) feasible = [(r["trial"], r["accuracy"]) for r in rec1 if r["model_size"] best_acc: best_acc = acc[i]; pareto_idx.append(i) plt.figure(figsize=(7, 5)) plt.scatter(size, acc, c="lightgray", label="all trials") plt.scatter(size[pareto_idx], acc[pareto_idx], c="crimson", zorder=3, label="Pareto front") plt.plot(size[pareto_idx], acc[pareto_idx], "--", c="crimson", alpha=0.6) plt.xlabel("model_size (lower = cheaper)"); plt.ylabel("accuracy (higher = better)") plt.title("Study 2 — accuracy vs. model size trade-off") plt.legend(); plt.grid(alpha=0.3); plt.tight_layout(); plt.show() We move from single-objective optimization to multi-objective optimization by jointly maximizing accuracy and minimizing model size. We use Ax to search for configurations that represent strong trade-offs between predictive performance and computational footprint. We then calculate and visualize the empirical Pareto frontier to understand how accuracy varies with model size. Copy CodeCopiedUse a different Browser print("\n=== Study 3: parameter constraints on a synthetic surface ===") c3 = Client() c3.configure_experiment( parameters=[ RangeParameterConfig(name="x1", bounds=(0.0, 1.0), parameter_type="float"), RangeParameterConfig(name="x2", bounds=(0.0, 1.0), parameter_type="float"), ], parameter_constraints=["x1 + x2 <= 1.5"], name="constrained_surface", ) c3.configure_optimization(objective="-dist") for _ in range(14): for idx, p in c3.get_next_trials(max_trials=1).items(): dist = (p["x1"] - 0.9) 2 + (p["x2"] - 0.9) 2 c3.complete_trial(trial_index=idx, raw_data={"dist": float(dist)}) bp, _, _, _ = c3.get_best_parameterization() print(f"Best point: x1={bp['x1']:.3f}, x2={bp['x2']:.3f}, " f"sum={bp['x1'] + bp['x2']:.3f} (constraint: <= 1.5)") print("Unconstrained optimum would be (0.9, 0.9); Ax respects the boundary.") We demonstrate parameter constraints using a simple two-dimensional synthetic optimization problem. We ask Ax to minimize the distance to a target point while enforcing the input constraint that the sum of the two variables remains below a boundary. We observe that the optimizer respects the constraint and finds the best feasible point near the constrained optimum. Copy CodeCopiedUse a different Browser print("\n=== Ax built-in analyses for Study 1 ===") try: import plotly.io as pio if "google.colab" in sys.modules: pio.renderers.default = "colab" cards = c1.compute_analyses(display=True) print(f"Computed {len(cards)} analysis cards.") except Exception as e: print("Interactive analyses didn't render in this environment:", e) print("(The matplotlib plots above already capture the key results.)") print("\n=== Saving / loading the experiment ===") try: c1.save_to_json_file("ax_study1.json") reloaded = Client.load_from_json_file("ax_study1.json") print("Saved to ax_study1.json and reloaded successfully.") rp, _, _, _ = reloaded.get_best_parameterization() print("Best params from reloaded client match:", rp == best_params) except Exception as e: print("JSON persistence API differs in this version:", e) print("See: https://ax.dev/docs/recipes/experiment-to-json") print("\nDone. You optimized a mixed-type search space with constraints, " "traced a Pareto frontier, and persisted in the experiment.") We use Ax’s built-in analysis tools to generate diagnostic cards, such as sensitivity, cross-validation, and other experiment insights, when the environment supports them. We then save the completed experiment to a JSON file and reload it to verify that the optimization state is preserved. We finish by confirming that the tutorial covers constrained optimization, multi-objective trade-offs, analysis, and experiment persistence. In conclusion, we developed a practical understanding of how Ax helps us run efficient and structured hyperparameter optimization experiments. We optimized a mixed-type search space, enforced both outcome and parameter constraints, compared accuracy against model size through multi-objective optimization, and identified trade-offs using an empirical Pareto frontier. We also used Ax’s analysis and persistence features to make the experimentation workflow more interpretable and reproducible. Check out the Full Codes here. Also, feel free to follow us on Twitter and don’t forget to join our 150k+ML SubReddit and Subscribe to our Newsletter. Wait! are you on telegram? now you can join us on telegram as well. Need to partner with us for promoting your GitHub Repo OR Hugging Face Page OR Product Release OR Webinar etc.? Connect with us The post Adaptive Experimentation with Meta’s Ax: A Practical Coding Guide appeared first on MarkTechPost.