Rename rank one up- and downdate functions for Cholesky to rank(up/down)date

[andreasnoack]

No description provided.

[jiahao]

I dislike having the rank prefix because it is a property of the quantity you do the up/down-date with and is not essential to the idea of a up/down-date. In principle there is nothing stopping you from computing a up/down-date with a low rank matrix.

[timholy]

updateAAt!?

[andreasnoack]

@jiahao I think it's pretty standard terminology for this operation, e.g. http://www.netlib.org/lapack/explore-html/d7/d15/group__double__blas__level2.html#ga35ca25bb135cd7bfdd5d6190b1aa4d07.

@timholy I don't like the name. I consider myself in a process of removing the As (and Bs) from Julia.

[jiahao]

@andreasnoack I don't see how the LAPACK page you linked to substantiates this operation being called a "rank update". If anything, the documentation clearly describes a "rank 1" operation (the 1 is missing from the function name) and the notion of update is not described in the main documentation (only in the description of the arguments).

Again, my point is that the phrase "rank update" is meaningless. "rank 1" is the adjectival phrase attached to "update"; "rank" itself cannot meaningfully describe any kind of update. That's why functions like "syrk" have the k - they are to describe operations dealing with "symmetric rank k" (the k cannot be omitted and still be a meaningful English phrase).

How about cholupdate! and choldowndate!? I don't like them as much as down/update!(::Cholesky), but I think we have to give the genericity issue a concession (at least, until Base.update! exists).

[jiahao]

I would even consider ranknupdate! less ugly than rankupdate!.

[andreasnoack]

The k versus 1 is in the signature here.

[jiahao]

But that's exactly my point regarding the name rankupdate, vs ranknupdate or rank1update.

[andreasnoack]

After offline discussions, we have settled (locally) for lowrank(up/down)date. It's a bit long, but I prefer a slightly long name to a cryptic name with abbreviations.