Nix flake (#40)

* Nix flake

* Nix: only add Accelerate framework on macOS

* Nix: development shel, direnv and compatibility

* Nix: use python packages supplied by withPackages

* Nix: remove channel compatibility

* Nix: fix ARM neon dotproduct on macOS

---------

Co-authored-by: Pavol Rusnak <pavol@rusnak.io>

flake.nix

@@ -0,0 +1,48 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+        llama-python = pkgs.python310.withPackages (ps: with ps; [
+          torch
+          numpy
+          sentencepiece
+        ]);
+      in
+      {
+        packages.default = pkgs.stdenv.mkDerivation {
+          name = "llama.cpp";
+          src = ./.;
+          nativeBuildInputs = with pkgs; [ cmake ];
+          buildInputs = with pkgs; lib.optionals stdenv.isDarwin [
+            darwin.apple_sdk.frameworks.Accelerate
+          ];
+          cmakeFlags = with pkgs; lib.optionals (system == "aarch64-darwin") [
+            "-DCMAKE_C_FLAGS=-D__ARM_FEATURE_DOTPROD=1"
+          ];
+          installPhase = ''
+            mkdir -p $out/bin
+            mv llama $out/bin/llama
+            mv quantize $out/bin/quantize
+            echo "#!${llama-python}/bin/python" > $out/bin/convert-pth-to-ggml
+            cat ${./convert-pth-to-ggml.py} >> $out/bin/convert-pth-to-ggml
+            chmod +x $out/bin/convert-pth-to-ggml
+          '';
+        };
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            cmake
+            llama-python
+          ] ++ lib.optionals stdenv.isDarwin [
+            darwin.apple_sdk.frameworks.Accelerate
+          ];
+        };
+      }
+    );
+}