Simple CMakeLists.txt

[vsoch]

Hi! I'm looking to build this with nix, and the way you have the custom install (running the bash script) is not ideal (it largely won't work). Can you share the most vanilla method to get this built with a standard cmake command? Apologies I'm not a heavy cmake user so I don't really know how it works. Thanks!

[cyrush]

Sure thing, our github actions for windows CI setup seems like a a good example:

conduit/.github/workflows/windows.yml

Line 21 in 36a58a4

cmake -S src -B build `

If you want to enable more features, you can pass them with cmake args like:

-DHDF5_DIR=path/to/hdf5/install

Here is a list of the options (which I should convert to a table to make them easier to read!)

https://llnl-conduit.readthedocs.io/en/latest/building.html#build-options

[vsoch]

Ah that's perfect - I'll keep this bookmarked! I wound up using a trick to cd into the src directory first, and then nix makes the build directory there and the ../ points to where it needs to be. And I think I got most of the basics with respect to flags https://github.com/rse-ops/nix/blob/0405825e4ff284e0e937c60baa78d2cbfa3c7e7a/pkgs/hpc/conduit/default.nix#L80-L92 and the bug I ran into was that when MPI was turned on, I think (blt?) couldn't find a bunch of symbols, telling me that one of those extra options was missing for it. I noticed that spack uses the tarball with blt so I am following suit, and I think my bug in building with MPI is that I need to possibly add more paths for it? E.g., there is quite a bit of logic here! https://github.com/spack/spack/blob/4bf964e6b36e8756b014c2e30343507c1cb71b03/var/spack/repos/builtin/packages/conduit/package.py#L468.

I got the basic build working (without MPI) and I'm hoping to go back to it and have MPI work too - I'm just kind of terrible with Cmake and new to Nix! 😆

[cyrush]

Glad that helped!

For MPI, the best path is to set cmake opts:

-DMPI_C_COMPILER=zzz
-DMPI_CXX_COMPILER=zzz
-DMPI_Fortran_COMPILER=zzz

to point to the MPI compiler wrappers (from mpich, etc)

The other case (usually on cray systems) is when you use compiler wrappers as the main compiler.
You pass the cray or mpi compiler wrapper to cmake as CMAKE_C_COMPILER (etc) instead of MPI_C_COMPILER (etc).

In this case you want ENABLE_FIND_MPI to be off. That tells cmake to "trust me, mpi exists but don't look for it!"

[vsoch]

Thank you! I've made a note in our repository and we are good to close here - I think this will mostly be me figuring out how nix achieves the same ability to get a prefix / etc for a package. I'll come back in the future if I have another question. Thanks for your help!