DOC Add hyper-parameter search example

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This adds a cuml.accel example that illustrates the point that using cuml.accel makes it easier to do things because you aren't interrupted by things taking forever and forever.

It uses a simple pipeline that can be fully GPU accelerated and then searches a few hyper-parameter combinations for that pipeline.

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• docs/source/cuml-accel/examples/index.rst

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• docs/source/cuml-accel/examples/index.rst

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📝 Walkthrough

Summary by CodeRabbit

• Documentation
  • Added a new example notebook demonstrating accelerated randomized hyperparameter tuning for an end-to-end preprocessing + classification workflow, including inspecting top configurations and evaluating the best model on a held-out test set.
  • Included the notebook in the examples documentation navigation so it appears alongside other tutorials.

Walkthrough

Adds a new Jupyter notebook demonstrating accelerated hyperparameter search with cuml.accel: loads the Forest Cover Type dataset (300k subsample), builds a StandardScaler→PCA→KNeighbors pipeline, runs RandomizedSearchCV (20 iter, 5-fold) and evaluates the refit model; registers the notebook in the examples index.

Changes

Hyperparameter Search Example

Layer / File(s)	Summary
Introduction and dataset preparation docs/source/cuml-accel/examples/hyperparameter_search.ipynb	Introduces the accelerated hyperparameter search use case, three-stage pipeline, and dataset. Loads Forest Cover Type via fetch_covtype, subsamples to 300k rows, and creates stratified 80/20 train/test splits.
Model pipeline and hyperparameter search docs/source/cuml-accel/examples/hyperparameter_search.ipynb	Constructs a scikit-learn Pipeline with StandardScaler, PCA, and KNeighborsClassifier. Declares param_distributions for PCA components and KNN hyperparameters. Runs RandomizedSearchCV with n_iter=20, cv=5, scoring="accuracy", random_state=42, n_jobs=1, and refit=True after enabling %load_ext cuml.accel.
Results inspection, evaluation, and registration docs/source/cuml-accel/examples/hyperparameter_search.ipynb, docs/source/cuml-accel/examples/index.rst	Prints search.best_params_ and search.best_score_, converts search.cv_results_ to a DataFrame and shows top-ranked configurations, evaluates the refit best model on the test set with search.score, includes notebook metadata, and adds the notebook to the examples .. toctree::.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Suggested reviewers

• jcrist

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a documentation example for hyperparameter search with cuml.accel.
Description check	✅ Passed	The description is related to the changeset, explaining the purpose of the new example and how it demonstrates cuml.accel benefits.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@docs/source/cuml-accel/examples/hyperparameter_search.ipynb`:
- Around line 32-34: Update the two benchmark sentences that read "Without
`cuml.accel`, this search takes ~4.5 minutes" and "With `cuml.accel` enabled the
same search completes in ~30 seconds" to clearly state these are example results
from a specific test machine/configuration (e.g., "On our test machine (specify
CPU/GPU, n_jobs, and other relevant config), this search took ~4.5 minutes; with
`cuml.accel` enabled it completed in ~30 seconds"), and apply the same qualified
wording to the later occurrence of the timing text (the similar lines around the
second mention) so readers understand timings are hardware/setup dependent.

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• docs/source/cuml-accel/examples/hyperparameter_search.ipynb
• docs/source/cuml-accel/examples/index.rst

[jcrist]

[jcrist]

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