Out of memory when multiplying matrix and vector

[Ricardo Fodra]

Why am I running out of memory when I multiply a sparse matrix and a vector:

sage: A
71604 x 143208 sparse matrix over Real Field with 53 bits of precision (use the '.str()' method to see the entries)
sage: A.density()
95465/3418088544
sage: x0
143208 x 1 dense matrix over Real Field with 53 bits of precision (use the '.str()' method to see the entries)
sage: x1 = A * x0

(after a while... out of memory)

[David Roe]

Try making x0 sparse before multiplying; when you multiply sparse by dense by default Sage turns the spare object into a dense one rather than the dense into sparse.

David

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