nix-par

default.nix

let
  pkgs = import <nixpkgs> {};
  lib = pkgs.lib;
  mkSystem = n: import <nixpkgs/nixos> {
    configuration = {
      networking.hostName = "dummy_${toString n}";
      fileSystems."/" = {
        device = "/dev/sda1";
        fsType = "ext4";
      };
      boot.loader.grub.device = "/dev/sda";
    };
  };
  systems = map mkSystem (lib.range 0 10);
  toplevels = map (x: x.config.system.build.toplevel) systems;
in {
  inherit systems toplevels;
  one = builtins.elemAt toplevels 0;
}

gistfile1.txt

[clever@amd-nixos:~/iohk/nix-par]$ time nix-instantiate default.nix -A toplevels
warning: you did not specify ‘--add-root’; the result might be removed by the garbage collector
/nix/store/c9nzzsgk0pwpkj5s19h186q38n29iq7a-nixos-system-dummy_0-18.03pre125026.f607771d0f5.drv
/nix/store/p5c6sj16iqpqawmw0kzvc3l4xibgji8g-nixos-system-dummy_1-18.03pre125026.f607771d0f5.drv
/nix/store/xlb5fhdfvvixymfk07k34zxcqshihwsp-nixos-system-dummy_2-18.03pre125026.f607771d0f5.drv
/nix/store/24yhqvp401mvkx8h7bz10w1q6lqp407w-nixos-system-dummy_3-18.03pre125026.f607771d0f5.drv
/nix/store/yq2gqzsindyns811pj56xvmdv1wc2wc1-nixos-system-dummy_4-18.03pre125026.f607771d0f5.drv
/nix/store/9fzpax0svyq1p87n4zyfqp4inb8sbwgs-nixos-system-dummy_5-18.03pre125026.f607771d0f5.drv
/nix/store/r3ckk1kcif980y0w0s0z8lh273cfnh0r-nixos-system-dummy_6-18.03pre125026.f607771d0f5.drv
/nix/store/h2pmkybpp91z968w0ns96nds32i7v0d7-nixos-system-dummy_7-18.03pre125026.f607771d0f5.drv
/nix/store/q3dk2g7qii7kfyll77937jda9r7b3y3w-nixos-system-dummy_8-18.03pre125026.f607771d0f5.drv
/nix/store/wy872cwv8b5wwrlp28blxya8hwqiq2r7-nixos-system-dummy_9-18.03pre125026.f607771d0f5.drv
/nix/store/489iwvw9vr7wl6wcaia3gvc31yzymzwq-nixos-system-dummy_10-18.03pre125026.f607771d0f5.drv

real    0m24.480s
user    0m36.686s
sys     0m1.263s

[clever@amd-nixos:~/iohk/nix-par]$ time nix-instantiate default.nix -A one
warning: you did not specify ‘--add-root’; the result might be removed by the garbage collector
/nix/store/c9nzzsgk0pwpkj5s19h186q38n29iq7a-nixos-system-dummy_0-18.03pre125026.f607771d0f5.drv

real    0m3.182s
user    0m1.873s
sys     0m0.361s