module SparseMatrix should be renamed

[lindahua]

Currently, Julia base has a submodule named SparseMatrix. This name is problematic in several ways:

• It violates the convention that a module name should use plural form when the name can be a name of certain type of entities.
• We are working on introducing SparseVector into Base (see [WIP] SparseVector #11424). It is really inconsistent and confusing to have a module named SparseMatrix while a type within that module named SparseVector.
• We have StridedMatrix, DenseMatrix, and Matrix, which are all types, while SparseMatrix is a module ...

I propose to rename this sub-module to Sparse or SparseArrays. (Personally, I prefer the former, which is both concise and informative).

[tkelman]

This will break package/user code and should not be done prior to 0.4. There's an unfortunately-named CHOLMOD.Sparse type that conflicts with this as well. The plural thing is really a guideline more than a hard rule, I don't think that matters much here. I'd prefer SparseArrays or similar, since Sparse is too short, too general, and it's an adjective.

[lindahua]

I am ok with SparseArrays, and also fine with doing the renaming post-v0.4.

[ViralBShah]

I am ok with renaming, but post 0.4.

[andreasnoack]

CHOLMOD.Sparse is not exported so there is not a conflict. The type names in the CHOLMOD module are chosen such that they correspond to the names of the structs in CHOLMOD. I think SparseArrays is fine.

[ScottPJones]

👍 to SparseArrays, post v0.4 (very good to see @lindahua having time for Julia again!)

[StefanKarpinski]

I somewhat prefer Sparse over SparseArrays. I'm trying to think of something else that Sparse might plausibly refer to and having a hard time coming up with anything.

[tkelman]

I've seen people use the term sparse to refer to missing-data situations, which bugs me a little because the implementations are usually quite different. Or sparse coding in the compressed sensing literature, LASSO methods etc where you end up with results that are sparse in values, but not (usually) in representation.

And it's likely confusing to have both a sparse function and a Sparse module, like we saw recently with pipe/Pipe. CHOLMOD.Sparse isn't exactly a conflict since it's not exported, but while working inside the cholmod-related files there's some potential ambiguity.

[johnmyleswhite]

I agree with @tkelman: the word sparse is used for a lot of things that aren't related to array storage.

[ViralBShah]

Bump. We should do this soon and early in the cycle.

[tkelman]

Closed by #13440