nix.md

Installing/compiling on NixOS

Nix is a declarative package manager.

Elmer variants included

default

Barebones Elmer with OpenMP and MPI support.

gui

Elmer with GUI.

full

A derivation with more parallel computing features such as HYPRE.

All derivations have Elmer/Ice.

Specifying no variant implies the default derivation.

Nix overlay

The Nix flake exposes an overlay which contains the three Elmer variants under the following package names: elmer, elmer-gui, elmer-full.

Binary cache

Add the following to your Nix config to use the Elmer binary cache.

nix.settings = {
  substituters = [ "https://elmerfem.cachix.org" ];
  trusted-public-keys = [ "elmerfem.cachix.org-1:nWIb5JzEzC2/W6qiuaC0urJRG+S7KvTn9WatX43gkHk=" ];
};

Building of Elmer with Nix

Compiling from upstream

nix build github:ElmerCSC/elmerfem for the default variant, or nix build github:ElmerCSC/elmerfem#<variant>.

After building, the binaries are accessible under result/bin.

Compiling in a local repository

In the local Elmer repository run nix build or nix build .#<variant>.

Verbose output

By default nix build only shows one line of the build output at once. To enable more verbose output, add the -L flag to the end of the build command.

For developers

Running tests

All tests

nix flake check -L

Specific variant

nix eval --raw .#checks.x86_64-linux.<variant>

Updating nixpkgs

• Edit the nixpkgs URL in flake.nix

  • Find the line nixpkgs.url = "github:NixOS/nixpkgs/nixos-XX.YY";.

  • Change XX.YY to the new nixpkgs release.

• Run nix flake update in the root of the repository.

• Check that everything works by running nix flake check -L.

Adding new dependencies or build flags

• Find the variant you want to patch.

  • The derivation declarations are in the form <variant> = {doCheck ? false}: { ....

• Add compile time dependencies to nativeBuildInputs.

• Add runtime dependencies to buildInputs.

• Add CMake flags to cmakeFlags.