forum.alglib.net

Hi,

First of all, I've been using Alglib for the last year and find it really powerful.

That being said, there is one capability I miss regarding the sparse matrix subpackage (maybe because of my own ignorance).
I would like to enumerate a particular row of a CRS matrix without having to enumerate the whole matrix. This should be straightforward to implement for the CRS format.
An alternative would be to directly have access to the data, column indices and pointers. Is that possible?

Hello!

You choose right time for proposal :) ALGLIB 3.9.0 will be released within few days, and it's a last moment for minor changes like one proposed by you.

There already exists sparsegetrow() function, but it returns entire row in dense format. I think that it is worth adding sparsegetcompressedrow() which will return just one row in compressed format (only nonzero entries).

Thank you for the fast answer!

Well, the idea is, for each row of the CRS matrix, to perform an operation (not necessarily in-place) only for the non-zero elements of the row.
So an iterator on the non-zero elements (and their position) of the row would be the best (since no copy is needed), or at least a copy of the row as a CRS matrix on which one could use sparseenumerate, as you suggested.

Thank you again!

I think that returning entire row in compressed format will be faster than performing iteration (less function call/check overhead).

Great! Looking forward to the new version!

ALGLIB for VBA is quite old (many years old), misses most functionality present in modern ALGLIB versions. As far as I remember, it misses constrained LM functionality. Only unconstrained fits are performed.