Estoy tratando de aplicar PCA en una gran matriz dispersa, en el siguiente enlace dice que randomizedPCA de sklearn puede manejar una matriz dispersa de formato disperso scipy.Aplique PCA en una matriz dispersa muy grande

Sin embargo, siempre recibo un error. ¿Alguien puede señalar lo que estoy haciendo mal?

La matriz de entrada 'X_train' contiene números en float64:

>>>type(X_train)
<class 'scipy.sparse.csr.csr_matrix'>
>>>X_train.shape
(2365436, 1617899)
>>>X_train.ndim 
2
>>>X_train[0]     
<1x1617899 sparse matrix of type '<type 'numpy.float64'>'
    with 81 stored elements in Compressed Sparse Row format>

Estoy tratando de hacer:

>>>from sklearn.decomposition import RandomizedPCA
>>>pca = RandomizedPCA()
>>>pca.fit(X_train)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/RT11/.pyenv/versions/2.7.9/lib/python2.7/site-packages/sklearn/decomposition/pca.py", line 567, in fit
    self._fit(check_array(X))
  File "/home/RT11/.pyenv/versions/2.7.9/lib/python2.7/site-packages/sklearn/utils/validation.py", line 334, in check_array
    copy, force_all_finite)
  File "/home/RT11/.pyenv/versions/2.7.9/lib/python2.7/site-packages/sklearn/utils/validation.py", line 239, in _ensure_sparse_format
    raise TypeError('A sparse matrix was passed, but dense '
TypeError: A sparse matrix was passed, but dense data is required. Use X.toarray() to convert to a dense numpy array.

Si trato de convertir a matriz densa, creo que no tengo memoria.

>>> pca.fit(X_train.toarray())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/RT11/.pyenv/versions/2.7.9/lib/python2.7/site-packages/scipy/sparse/compressed.py", line 949, in toarray
    return self.tocoo(copy=False).toarray(order=order, out=out)
  File "/home/RT11/.pyenv/versions/2.7.9/lib/python2.7/site-packages/scipy/sparse/coo.py", line 274, in toarray
    B = self._process_toarray_args(order, out)
  File "/home/RT11/.pyenv/versions/2.7.9/lib/python2.7/site-packages/scipy/sparse/base.py", line 800, in _process_toarray_args
    return np.zeros(self.shape, dtype=self.dtype, order=order)
MemoryError