lsolve, usolve for non-square matrices?

[mike239x]

It seems lsolve and usolve are only working for the square matrices.

Why is it so? I think it should work for non-square matrices as well.

Well, the important one is the usolve, because if you use LU decomposition
(in my case using lup), you get square L matrix and non-square U matrix.

[mike239x]

This is pretty easy to fix by simple adding some zeros to make the matrix square either adding/removing zeros here and there.

[josdejong]

I don't know why the current implementation only supports square matrices, but if it's easy to add support for non-square matrices that would be a great extension.

@mike239x would you be interested in giving it a try and extend lsolve and usolve?

[mike239x]

@josdejong Right now I created my self-made implementation with some additional restrictions, so that it would be enough for me, later I can do that. Right now kinda busy with my bachelor thesis, my bad.
You can assign this task to me if you want.

[josdejong]

👍

Let's just keep it open. If anyone can pick this up before Mike can please drop a message here.

[a8t]

I wouldn't mind attempting, but I encourage others to hop on as well. Been a few years since I graduated, haven't done much matrix math since... 😅

[cshaa]

This should be relatively easy to implement, the algorithms needed are already implemented in lsolveAll and usolveAll. They generalize well to the case of rectangular matrices, as described here, somebody just needs to implement it :)

If anyone's up for the task, I'll happily help them understand the current code and what needs to be done exactly.