Sparse matrix vector product returns null.
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cTroels
el 25 de Mzo. de 2024
Comentada: John D'Errico
el 25 de Mzo. de 2024
Hi.
I am computing a sparse matrix vector product.
The product is between a NXN matrix, M, and Nx1 vector, V. When computing the product for a sparse matrix M, matlab returns a empty Nx0 vector. When computing the same product, but using full(M), it returns a non-zero Nx1 vector.
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John D'Errico
el 25 de Mzo. de 2024
Editada: John D'Errico
el 25 de Mzo. de 2024
As is so often the case, probable user error. Almost certainly you have made a mistake. One of your matrices or vectors is not what you think it is.
So IF you really want a useful answer, then post the matrix and the vector, in a .mat file. Without that, we cannot verify that what you say happens, and then we are left with only the obvious conclusion: PROBABLE USER ERROR.
Along the way, if I were you, I would verify that the sparse and full versions of the matrix really are the same things, and that they have the shape and sizes you think they have. Then I would verify the same for the vector. Are you POSITIVE the vector is not a Nx0 vector, thus an empty vector? For example, it is quite easy to create an nx0 vector.
V = zeros(10,0)
whos V
It really is far too common here that someone sees something they do not expect, then jumps to the conclusion the problem MUST be in the software, since the user could not possibly have made a mistake.
Respuesta aceptada
Bruno Luong
el 25 de Mzo. de 2024
Editada: Bruno Luong
el 25 de Mzo. de 2024
"What can cause this issue?"
Nothing. What you claim likely would not happen.
Unless if you show an example.
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