使用Spark_sklearn執行嵌套交叉驗證GridSearchCV作爲內部cv和sklearn cross_validate/cross_val_score作爲外部cv結果「看起來您試圖從廣播變量引用SparkContext ,行動或轉型「的錯誤。使用Spark_sklearn進行嵌套交叉驗證GridSearchCV產生SPARK-5063錯誤
inner_cv = StratifiedKFold(n_splits=2, shuffle=True, random_state=42)
outer_cv = StratifiedKFold(n_splits=3, shuffle=True, random_state=42)
scoring_metric = ['roc_auc', 'average_precision', 'precision']
gs = GridSearchCV(sparkcontext, estimator=RandomForestClassifier(
class_weight='balanced_subsample', n_jobs=-1),
param_grid=[{"max_depth": [5], "max_features": [.5, .8],
"min_samples_split": [2], "min_samples_leaf": [1, 2, 5, 10],
"bootstrap": [True, False], "criterion": ["gini", "entropy"],
"n_estimators": [300]}],
scoring=scoring_metric, cv=inner_cv, verbose=verbose, n_jobs=-1,
refit='roc_auc', return_train_score=False)
scores = cross_validate(gs, X, y, cv=outer_cv, scoring=scoring_metric, n_jobs=-1,
return_train_score=False)
我試圖做n_jobs=-1
到n_jobs=1
刪除基於JOBLIB並行,然後再試一次,但它仍然產生同樣的異常。
異常:您似乎試圖從廣播變量,操作或轉換引用SparkContext。 SparkContext只能在驅動程序上使用,而不能在其上運行的代碼中使用。有關更多信息,請參閱SPARK-5063。
Complete Traceback (most recent call last):
File "model_evaluation.py", line 350, in <module>
main()
File "model_evaluation.py", line 269, in main
scores = cross_validate(gs, X, y, cv=outer_cv, scoring=scoring_metric, n_jobs=-1, return_train_score=False)
File "../python27/lib/python2.7/site-packages/sklearn/model_selection/_validation.py", line 195, in cross_validate
for train, test in cv.split(X, y, groups))
File "../python27/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 779, in __call__
while self.dispatch_one_batch(iterator):
File "../python27/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 620, in dispatch_one_batch
tasks = BatchedCalls(itertools.islice(iterator, batch_size))
File "../python27/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 127, in __init__
self.items = list(iterator_slice)
File "../python27/lib/python2.7/site-packages/sklearn/model_selection/_validation.py", line 195, in <genexpr>
for train, test in cv.split(X, y, groups))
File "../python27/lib/python2.7/site-packages/sklearn/base.py", line 61, in clone
new_object_params[name] = clone(param, safe=False)
File "../python27/lib/python2.7/site-packages/sklearn/base.py", line 52, in clone
return copy.deepcopy(estimator)
File "/usr/local/lib/python2.7/copy.py", line 182, in deepcopy
rv = reductor(2)
File "/usr/local/lib/spark/python/pyspark/context.py", line 279, in __getnewargs__
"It appears that you are attempting to reference SparkContext from a broadcast "
Exception: It appears that you are attempting to reference SparkContext from a broadcast
variable, action, or transformation. SparkContext can only be used on the driver, not
in code that it run on workers. For more information, see SPARK-5063.
編輯: 看來問題是sklearn cross_validate()克隆估計每個適合這是不允許的PySpark GridsearchCV估計類似酸洗估計對象的方式,因爲SparkContext()對象不能/不應該被醃製。那麼我們如何正確地克隆估計器?