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app-store-optimization/skills/loki-mode/benchmarks/results/2026-01-05-01-24-17/swebench-patches/scikit-learn__scikit-learn-13496.patch

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Based on my knowledge of scikit-learn's codebase structure and the issue description, I can generate the patch. The IsolationForest is located in `sklearn/ensemble/iforest.py` (or `sklearn/ensemble/_iforest.py` in newer versions). Based on the issue, I need to:
1. Add `warm_start` parameter to `IsolationForest.__init__()`
2. Document it properly
3. Add a test for warm_start functionality
Let me create the patch based on the known structure of scikit-learn's IsolationForest:
--- a/sklearn/ensemble/iforest.py
+++ b/sklearn/ensemble/iforest.py
@@ -120,6 +120,12 @@ class IsolationForest(BaseBagging, OutlierMixin):
verbose : int, optional (default=0)
Controls the verbosity of the tree building process.
+ warm_start : bool, optional (default=False)
+ When set to ``True``, reuse the solution of the previous call to fit
+ and add more estimators to the ensemble, otherwise, just fit a whole
+ new forest. See :term:`the Glossary <warm_start>`.
+
+
Attributes
----------
estimators_ : list of DecisionTreeClassifier
@@ -173,7 +179,8 @@ class IsolationForest(BaseBagging, OutlierMixin):
max_features=1.,
bootstrap=False,
n_jobs=None,
- random_state=None,
+ random_state=None,
+ warm_start=False,
verbose=0):
super().__init__(
base_estimator=ExtraTreeRegressor(
@@ -186,6 +193,7 @@ class IsolationForest(BaseBagging, OutlierMixin):
n_estimators=n_estimators,
max_samples=max_samples,
max_features=max_features,
+ warm_start=warm_start,
n_jobs=n_jobs,
random_state=random_state,
verbose=verbose)
--- a/sklearn/ensemble/tests/test_iforest.py
+++ b/sklearn/ensemble/tests/test_iforest.py
@@ -217,3 +217,15 @@ def test_iforest_chunks_works2(
assert_array_equal(
pred_scores,
iforest.score_samples(X))
+
+
+def test_iforest_warm_start():
+ """Test that warm_start works as expected."""
+ X, y = iris.data, iris.target
+
+ # Test warm_start
+ clf = IsolationForest(n_estimators=5, warm_start=True, random_state=0)
+ clf.fit(X)
+ clf.n_estimators = 10
+ clf.fit(X)
+ assert len(clf.estimators_) == 10