2012/1/9 Peter Prettenhofer <[email protected]>: > 2012/1/8 Mathieu Blondel <[email protected]>: >> If I'm not mistaken (I just read the source code on github), the copy >> that Peter is experiencing is due to ravel() in this method: >> https://github.com/scipy/scipy/blob/master/scipy/sparse/compressed.py#L264 >> >> This method in turn invokes csr_matvecs which is implemented here: >> https://github.com/scipy/scipy/blob/master/scipy/sparse/sparsetools/csr.h#L1010 >> >> This method takes a sparse matrix and a flat array (C-style ordered) >> as inputs. The advantage of using ravel() here is that another >> implementation is not needed to handle Fortran-style arrays. However, >> it does result in a copy. >> >> In predict, SGDClassifier does a safe_sparse_dot(X, self.coef_.T). >> Therefore, if coef_ is Fortran-style, coef_.T becomes C-style, which >> is the format expected by ravel() to avoid a copy. > > I just checked: The issue does only apply to multi class classification! > For binary classification ``coef_`` is a one dimensional array which > is both c and fortran style. > > ``ravel`` is only used in the binary case so it is not responsible for > the copy. >
BTW: I just looked at csr_matrix.__mul__ and sparse.compressed._mul_multivector - there are ravels all over the place that trigger a copy of the view. -- Peter Prettenhofer ------------------------------------------------------------------------------ Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox _______________________________________________ Scikit-learn-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/scikit-learn-general
