Nix Flake for Running EMerge

[mayl]

First of all, thanks for this package. I haven't actually done any of my own simulations with it, but as a professional EE I think it's very exciting to be able to do EM simulation without a giant budget!

I use NixOS on my home computers, and have gotten EMerge to run in a flake. The repo is here. Nix users can run nix develop github:mayl/EMerge_Nix_Flake and it will build everything needed to drop them in a shell with a python capable of running all the Example Pack examples (except demo12 and demo17 which I think use deprecated EMerge features? haven't looked into it yet). The only "extra" the flake supports for now is UMFPACK, but that works (I changed the solver in a couple examples).

It was the first thing I tried using Claude-Code for, so there's that... I've packaged a fair amount of stuff with nix before, so I was able to keep a pretty close eye on it, but if that's not your thing be aware that's how I made it I guess.

Just wanted to share it in case it's useful to other Nix users out there who are also interested in EMerge!

[FennisRobert]

Hey! Great work. Good to hear you could also get UMFPACK to work. Was it tricky? I don't have any Linux like systems myself so any guidance on steps required to install UMFPACK are welcome.

Regarding demo12 and 17, I found a bug in the latest version of EMerge. I'm patching now to 2.3.2 which should resolve the issue. Let me know if it persists!

[mayl]

It was a little tricky - the upstream version of suitesparse packaged by nixpkgs is very out of date, so old that it still only has the old MAKE build system. That old build system doesn't generate package config files so scikit-umfpack's meson build can't find it. I build suitesparse in the flake that's newer and has the CMAKE build system which puts out the pkg-config files. From there it's pretty standard to inject the library into the right places to get it to work. Of course, now that is all done you can just nix develop and get the full setup.

Nix is pretty idiosyncratic, so I don't think this build really applies much to other Linuxes.

I'll give the new version a try and report if the examples work.

[FennisRobert]

Iffff you want, you could write a Markdown instruction manual on how to get this all to work on Linux with your name on it of course. I'll put it on my website and in the Github somewhere. If you don't feel like writing the whole document, you can also give me the step summary, then I'll write some text around it. I don't have Linux computers myself and I am surprisingly bad with computers so this would be tremendously helpful!

[mayl]

Sure I can write something, probably this weekend. Again, this is very particular to Nix (https://nixos.org/) and probably less applicable to other linux distributions.

The brief sketch:

1. Install the nix tool, either from your distribution's package manager (apt, pacman or whatever) or using the determinate nix installer.
2. run nix dev github:mayl/emerge_nix_flake*. You are now in an shell with python pre-configured to run EMerge and UMFPACK.

It can take a while for the environment to build the first time (compiles suitesparse), but just pulls the compiled suitesparse from the nix store cache after that. Also, this is a standard Nix thing but EMerge and suitesparse are only installed in the shell and if you exit the rest of your system is left untouched. There's more ways to use the flake, but they're all pretty standard Nix flakes things and documented in my README.

I don't know if you saw, but my flake is now building EMerge and SuiteSparse in Github Actions CI. If you modified the examples to take a --headless flag to let them run without stopping to open the results windows it wouldn't be much of a stretch to check that all the examples work in CI...

*you might need to use the --extra-experimental-features "nix-command flakes" if you didn't use determinate nix and don't have flakes enabled.

[mayl]

The latest Emerge Commit fixes demo17 for me.

I seem to have the same error with demo12:

Traceback (most recent call last):
  File "/home/larry/projects/claude/EMergeFlake/EMerge_2_0_Example_Pack/examples/demo12_mode_alignment.py", line 71, in <module>
    m.display.add_portmode(p1, 30, k0=data.field[0].k0, mode_number=i)
  File "/nix/store/1097w8kfr0q9dl6g3r86l5li60s8m64c-emerge-env/lib/python3.11/site-packages/emerge/_emerge/plot/pyvista/display.py", line 306, in add_portmode
    F = port.port_mode_3d_global(xf,yf,zf,k0, which=field, mode_nr=mode_number)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/1097w8kfr0q9dl6g3r86l5li60s8m64c-emerge-env/lib/python3.11/site-packages/emerge/_emerge/physics/microwave/microwave_bc.py", line 870, in port_mode_3d_global
    Ex, Ey, Ez = self.global_field_function(k0, which, mode_nr)(x_global,y_global,z_global)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/1097w8kfr0q9dl6g3r86l5li60s8m64c-emerge-env/lib/python3.11/site-packages/emerge/_emerge/physics/microwave/microwave_bc.py", line 760, in modef
    amplitudes = self.port_modes[mode_nr]
                 ~~~~~~~~~~~~~~~^^^^^^^^^
KeyError: 0

[FennisRobert]

I notice these are examples from the 2.0 example pack. Could you check the current demo12 on my Github page? I think this is due to an outdated file.

[mayl]

Success! The upstream example runs!

[mayl]

Obviously I haven't gotten to doing the manual page you asked for... Sorry about that, things have been busy.

I saw you announce 2.4, exciting stuff! As a suggestion, it would help if you tagged release commits in GitHub so when I build from source I can track a specific release.

[FennisRobert]

Don't worry! If its finished anywhere this year it would be fine haha.

I'll try but I have issues with github not showing me the tags to release.

Additionally, can you explain to me how you would use that? With python code there isnt really anything to build. Fyi, I am a complete noob when it comes to this stuff haha