Dimension mismatch error with scikit pipeline FeatureUnion - machine-learning

Question

This is my first post. I've been trying to combine features with FeatureUnion and Pipeline, but when I add a tf-idf + svd piepline the test fails with a 'dimension mismatch' error. My simple task is to create a regression model to predict search relevance. Code and errors are reported below. Is there something wrong in my code?
df = read_tsv_data(input_file)
df = tokenize(df)
df_train, df_test = train_test_split(df, test_size = 0.2, random_state=2016)
x_train = df_train['sq'].values
y_train = df_train['relevance'].values
x_test = df_test['sq'].values
y_test = df_test['relevance'].values
# char ngrams
char_ngrams = CountVectorizer(ngram_range=(2,5), analyzer='char_wb', encoding='utf-8')
# TFIDF word ngrams
tfidf_word_ngrams = TfidfVectorizer(ngram_range=(1, 4), analyzer='word', encoding='utf-8')
# SVD
svd = TruncatedSVD(n_components=100, random_state = 2016)
# SVR
svr_lin = SVR(kernel='linear', C=0.01)
pipeline = Pipeline([
('feature_union',
FeatureUnion(
transformer_list = [
('char_ngrams', char_ngrams),
('char_ngrams_svd_pipeline', make_pipeline(char_ngrams, svd)),
('tfidf_word_ngrams', tfidf_word_ngrams),
('tfidf_word_ngrams_svd', make_pipeline(tfidf_word_ngrams, svd))
]
)
),
('svr_lin', svr_lin)
])
model = pipeline.fit(x_train, y_train)
y_pred = model.predict(x_test)
When adding the pipeline below to the FeatureUnion list:
('tfidf_word_ngrams_svd', make_pipeline(tfidf_word_ngrams, svd))
The exception below is generated:
2016-07-31 10:34:08,712 : Testing ... Test Shape: (400,) - Training Shape: (1600,)
Traceback (most recent call last):
File "src/model/end_to_end_pipeline.py", line 236, in <module>
main()
File "src/model/end_to_end_pipeline.py", line 233, in main
process_data(input_file, output_file)
File "src/model/end_to_end_pipeline.py", line 175, in process_data
y_pred = model.predict(x_test)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/utils/metaestimators.py", line 37, in <lambda>
out = lambda *args, **kwargs: self.fn(obj, *args, **kwargs)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/pipeline.py", line 203, in predict
Xt = transform.transform(Xt)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/pipeline.py", line 523, in transform
for name, trans in self.transformer_list)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 800, in __call__
while self.dispatch_one_batch(iterator):
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 658, in dispatch_one_batch
self._dispatch(tasks)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 566, in _dispatch
job = ImmediateComputeBatch(batch)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 180, in __init__
self.results = batch()
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/externals/joblib/parallel.py", line 72, in __call__
return [func(*args, **kwargs) for func, args, kwargs in self.items]
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/pipeline.py", line 399, in _transform_one
return transformer.transform(X)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/utils/metaestimators.py", line 37, in <lambda>
out = lambda *args, **kwargs: self.fn(obj, *args, **kwargs)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/pipeline.py", line 291, in transform
Xt = transform.transform(Xt)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/decomposition/truncated_svd.py", line 201, in transform
return safe_sparse_dot(X, self.components_.T)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sklearn/utils/extmath.py", line 179, in safe_sparse_dot
ret = a * b
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/scipy/sparse/base.py", line 389, in __mul__
raise ValueError('dimension mismatch')
ValueError: dimension mismatch

Answer 1

What if you change second svd usage to new svd?
transformer_list = [
('char_ngrams', char_ngrams),
('char_ngrams_svd_pipeline', make_pipeline(char_ngrams, svd)),
('tfidf_word_ngrams', tfidf_word_ngrams),
('tfidf_word_ngrams_svd', make_pipeline(tfidf_word_ngrams, clone(svd)))
]
Seems your problem occurs because you're using same object 2 times. I is fitted first time on CountVectorizer, and second time on TfidfVectorizer (Or vice versa), and after you call predict of whole pipeline this svd object cannot understand output of CountVectorizer, because it was fitted on or TfidfVectorizer's output (Or again, vice versa).