Supporting PETSc older versions??

[abhyshr]

What versions of PETSc does GridPACK support and is there any reason to support PETSc version < 3.16? The develop branch is updated to use PETSc version 3.16. There is a flag

GridPACK/src/CMakeLists.txt

Line 303 in 46762bc

if (NOT USE_OLD_PETSC)

that checks for older versions of PETSc.

IMHO, I don't see a reason to support older PETSc versions. Which projects are using older PETSc versions? What will it take to migrate to using develop branch?

[wperkins]

IMO, we should drop the use of Jed Brown's FindPETSc and rely only on pkgconfig. However, I think PETSc $\ge$ 3.12 should be supported since that's the version in Ubuntu 20 LTS (supported thru 2024).

[abhyshr]

I agree. it was Jed who suggested me to use pkgconfig instead of FindPETSc :-) Can PETSc 3.16 not be built on Ubuntu 20 LTS? Which projects are using Ubuntu 20 LTS?

[wperkins]

Sure, you can build PETSc 3.16 on Ubuntu 20. However, I'm thinking about ease of installation, not specific projects. On Ubuntu, it's much easier to just install the PETSc package than to build. In fact, on Ubuntu 20, there is no need to build any prerequisites. Just use the system packages and have GridPACK build GA. The current GridPACK can be built with PETSc 3.12 -- 3.16 in my experience. I've not tried 3.18.

Is there something specific in the newer PETSc that we need/want to be using?

[abhyshr]

On Ubuntu, it's much easier to just install the PETSc package than to build.

What do you mean by this?

[wperkins]

This is all it takes: sudo apt install petsc-dev

[abhyshr]

Aah...I see. which version of PETSc does it install? PETSc development branch?

[abhyshr]

Can petsc-3.16 be installed? sudo apt install petsc-3.16 or something similar?

[abhyshr]

I am thinking a little ahead here (maybe) for what PETSc version GridPACK should support for the next release. As I mentioned in the call yesterday, we should have a release early next year.

[wperkins]

Can petsc-3.16 be installed? sudo apt install petsc-3.16 or something similar?

No. Only 3.12 is available AFAIK. There may be PPA source, but I haven't looked.

[wperkins]

I am thinking a little ahead here (maybe) for what PETSc version GridPACK should support for the next release. As I mentioned in the call yesterday, we should have a release early next year.

We can support 3.16 and maybe even 3.18, but I would like to retain compatibility with 3.12 for a while. I don't think this is hard to do.

[abhyshr]

Ok. It would be good to avoid using NOT USE_OLD_PETSC flags and other such stuff that make a distinction between which versions of PETSc are used. I think (and hope) that pkgconfig can handle PETSc >= 3.12 without having to resort to NOT USE_OLD_PETSC but I am not sure.

[wperkins]

Agreed. AFAIK, USE_OLD_PETSC only works for those versions of PETSc that produced a PetscConfig.cmake (or whatever) when built. I think that stopped in 3.10 or so.

[wperkins]

If #164 is merged, 3.14.x would be the minimum PETSc version allowed.