I've just sent a PR which implements Oliviers solution - The overhead (converting to f-style) only applies to multi-class classification so I think its ok to do it this way. SGDClassifier currently does not support `partial_fit` only via the `init_coef` and `init_intercept` arguments, they are automatically converted to c-style before they are used in model fitting so everything is fine.
As soon as I work on implementing partial_fit I'll refactor the whole thing to avoid mem copies whenever possible. https://github.com/scikit-learn/scikit-learn/pull/545 best, Peter 2012/1/9 Peter Prettenhofer <[email protected]>: > 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 -- 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
