Combine these to a single flag: maybe PCMS_ENABLE_TRANSFER

[Fuad-HH]

pcms/src/pcms/transfer/CMakeLists.txt

Line 23 in 7b5ff9f

if(PCMS_ENABLE_PETSC AND PCMS_ENABLE_MESHFIELDS)

Like this, there are many places in both cmake and c++ codebase where these two are used to determine if pcms::transfer is being enabled or not. Having a specific flag combining these two would be helpful.

[jacobmerson]

We may want to have a separate flag for enabling transfer overall, but we have already relaxed some of the constraints that required both of these libraries to perform transfer.

• Petsc is required for the transfer methods that require doing global solves (for now this is just projections).
• The mesh intersection variants only work with Omega_h meshes.
• The current version of the conservative transfer probably does require mesh fields for the integration, but eventually we can relax that for order 0/order one where we just use the barycentric coords from Omega_h. This is how we support evaluations without meshfields installed.

[jacobmerson]

@Fuad-HH and I had a productive offline discussion. the point he was trying to get across is that most of our PCMS_ENABLE flags are dependency / PCMS developer focused. However, for the end-user, they are going to be much more interested in capability focused ENABLE flags that help them to turn on the features they want.

For example, we could have a flag called PCMS_ENABLE_CONSERVATIVE_TRANSFER which when turned on would require that PCMS was configured with PETSC/MeshFields/Omega_h.

I think this is probably a fairly good idea. However, it will take a fair amount of effort to figure out what the appropriate capabilities should be called and then figure out how to get CMake to handle properly.

I am leaving this issue open for future discussion and potential coordination on how to accomplish this.