bogdan/micrograd.zig
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Bogdan Buduroiu 2026-06-09 17:58:59 +03:00
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use flake .

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# This file is for zig-specific build artifacts.
# If you have OS-specific or editor-specific files to ignore,
# such as *.swp or .DS_Store, put those in your global
# ~/.gitignore and put this in your ~/.gitconfig:
#
# [core]
# excludesfile = ~/.gitignore
#
# Cheers!
# -andrewrk
.zig-cache/
zig-out/
/release/
/debug/
/build/
/build-*/
/docgen_tmp/
.direnv/

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README.md Normal file
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# micrograd.zig
Implementing Karpathy's [micrograd](https://github.com/karpathy/micrograd) with some help from [0xdeb7ef/microgradz](https://github.com/0xdeb7ef/microgradz).
Scalar only implementation
## Setup
Allow direnv
```
direnv allow
```
## Build
```
zig build
```

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const std = @import("std");
// Although this function looks imperative, it does not perform the build
// directly and instead it mutates the build graph (`b`) that will be then
// executed by an external runner. The functions in `std.Build` implement a DSL
// for defining build steps and express dependencies between them, allowing the
// build runner to parallelize the build automatically (and the cache system to
// know when a step doesn't need to be re-run).
pub fn build(b: *std.Build) void {
// Standard target options allow the person running `zig build` to choose
// what target to build for. Here we do not override the defaults, which
// means any target is allowed, and the default is native. Other options
// for restricting supported target set are available.
const target = b.standardTargetOptions(.{});
// Standard optimization options allow the person running `zig build` to select
// between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
// set a preferred release mode, allowing the user to decide how to optimize.
const optimize = b.standardOptimizeOption(.{});
// It's also possible to define more custom flags to toggle optional features
// of this build script using `b.option()`. All defined flags (including
// target and optimize options) will be listed when running `zig build --help`
// in this directory.
// This creates a module, which represents a collection of source files alongside
// some compilation options, such as optimization mode and linked system libraries.
// Zig modules are the preferred way of making Zig code available to consumers.
// addModule defines a module that we intend to make available for importing
// to our consumers. We must give it a name because a Zig package can expose
// multiple modules and consumers will need to be able to specify which
// module they want to access.
const mod = b.addModule("micrograd_zig", .{
// The root source file is the "entry point" of this module. Users of
// this module will only be able to access public declarations contained
// in this file, which means that if you have declarations that you
// intend to expose to consumers that were defined in other files part
// of this module, you will have to make sure to re-export them from
// the root file.
.root_source_file = b.path("src/root.zig"),
// Later on we'll use this module as the root module of a test executable
// which requires us to specify a target.
.target = target,
});
// Here we define an executable. An executable needs to have a root module
// which needs to expose a `main` function. While we could add a main function
// to the module defined above, it's sometimes preferable to split business
// logic and the CLI into two separate modules.
//
// If your goal is to create a Zig library for others to use, consider if
// it might benefit from also exposing a CLI tool. A parser library for a
// data serialization format could also bundle a CLI syntax checker, for example.
//
// If instead your goal is to create an executable, consider if users might
// be interested in also being able to embed the core functionality of your
// program in their own executable in order to avoid the overhead involved in
// subprocessing your CLI tool.
//
// If neither case applies to you, feel free to delete the declaration you
// don't need and to put everything under a single module.
const exe = b.addExecutable(.{
.name = "micrograd_zig",
.root_module = b.createModule(.{
// b.createModule defines a new module just like b.addModule but,
// unlike b.addModule, it does not expose the module to consumers of
// this package, which is why in this case we don't have to give it a name.
.root_source_file = b.path("src/main.zig"),
// Target and optimization levels must be explicitly wired in when
// defining an executable or library (in the root module), and you
// can also hardcode a specific target for an executable or library
// definition if desireable (e.g. firmware for embedded devices).
.target = target,
.optimize = optimize,
// List of modules available for import in source files part of the
// root module.
.imports = &.{
// Here "micrograd_zig" is the name you will use in your source code to
// import this module (e.g. `@import("micrograd_zig")`). The name is
// repeated because you are allowed to rename your imports, which
// can be extremely useful in case of collisions (which can happen
// importing modules from different packages).
.{ .name = "micrograd_zig", .module = mod },
},
}),
});
// This declares intent for the executable to be installed into the
// install prefix when running `zig build` (i.e. when executing the default
// step). By default the install prefix is `zig-out/` but can be overridden
// by passing `--prefix` or `-p`.
b.installArtifact(exe);
// This creates a top level step. Top level steps have a name and can be
// invoked by name when running `zig build` (e.g. `zig build run`).
// This will evaluate the `run` step rather than the default step.
// For a top level step to actually do something, it must depend on other
// steps (e.g. a Run step, as we will see in a moment).
const run_step = b.step("run", "Run the app");
// This creates a RunArtifact step in the build graph. A RunArtifact step
// invokes an executable compiled by Zig. Steps will only be executed by the
// runner if invoked directly by the user (in the case of top level steps)
// or if another step depends on it, so it's up to you to define when and
// how this Run step will be executed. In our case we want to run it when
// the user runs `zig build run`, so we create a dependency link.
const run_cmd = b.addRunArtifact(exe);
run_step.dependOn(&run_cmd.step);
// By making the run step depend on the default step, it will be run from the
// installation directory rather than directly from within the cache directory.
run_cmd.step.dependOn(b.getInstallStep());
// This allows the user to pass arguments to the application in the build
// command itself, like this: `zig build run -- arg1 arg2 etc`
if (b.args) |args| {
run_cmd.addArgs(args);
}
// Creates an executable that will run `test` blocks from the provided module.
// Here `mod` needs to define a target, which is why earlier we made sure to
// set the releative field.
const mod_tests = b.addTest(.{
.root_module = mod,
});
// A run step that will run the test executable.
const run_mod_tests = b.addRunArtifact(mod_tests);
// Creates an executable that will run `test` blocks from the executable's
// root module. Note that test executables only test one module at a time,
// hence why we have to create two separate ones.
const exe_tests = b.addTest(.{
.root_module = exe.root_module,
});
// A run step that will run the second test executable.
const run_exe_tests = b.addRunArtifact(exe_tests);
// A top level step for running all tests. dependOn can be called multiple
// times and since the two run steps do not depend on one another, this will
// make the two of them run in parallel.
const test_step = b.step("test", "Run tests");
test_step.dependOn(&run_mod_tests.step);
test_step.dependOn(&run_exe_tests.step);
// Just like flags, top level steps are also listed in the `--help` menu.
//
// The Zig build system is entirely implemented in userland, which means
// that it cannot hook into private compiler APIs. All compilation work
// orchestrated by the build system will result in other Zig compiler
// subcommands being invoked with the right flags defined. You can observe
// these invocations when one fails (or you pass a flag to increase
// verbosity) to validate assumptions and diagnose problems.
//
// Lastly, the Zig build system is relatively simple and self-contained,
// and reading its source code will allow you to master it.
}

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.{
// This is the default name used by packages depending on this one. For
// example, when a user runs `zig fetch --save <url>`, this field is used
// as the key in the `dependencies` table. Although the user can choose a
// different name, most users will stick with this provided value.
//
// It is redundant to include "zig" in this name because it is already
// within the Zig package namespace.
.name = .micrograd_zig,
// This is a [Semantic Version](https://semver.org/).
// In a future version of Zig it will be used for package deduplication.
.version = "0.0.0",
// Together with name, this represents a globally unique package
// identifier. This field is generated by the Zig toolchain when the
// package is first created, and then *never changes*. This allows
// unambiguous detection of one package being an updated version of
// another.
//
// When forking a Zig project, this id should be regenerated (delete the
// field and run `zig build`) if the upstream project is still maintained.
// Otherwise, the fork is *hostile*, attempting to take control over the
// original project's identity. Thus it is recommended to leave the comment
// on the following line intact, so that it shows up in code reviews that
// modify the field.
.fingerprint = 0xe822f267c17f4cd9, // Changing this has security and trust implications.
// Tracks the earliest Zig version that the package considers to be a
// supported use case.
.minimum_zig_version = "0.16.0",
// This field is optional.
// Each dependency must either provide a `url` and `hash`, or a `path`.
// `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
// Once all dependencies are fetched, `zig build` no longer requires
// internet connectivity.
.dependencies = .{
// See `zig fetch --save <url>` for a command-line interface for adding dependencies.
//.example = .{
// // When updating this field to a new URL, be sure to delete the corresponding
// // `hash`, otherwise you are communicating that you expect to find the old hash at
// // the new URL. If the contents of a URL change this will result in a hash mismatch
// // which will prevent zig from using it.
// .url = "https://example.com/foo.tar.gz",
//
// // This is computed from the file contents of the directory of files that is
// // obtained after fetching `url` and applying the inclusion rules given by
// // `paths`.
// //
// // This field is the source of truth; packages do not come from a `url`; they
// // come from a `hash`. `url` is just one of many possible mirrors for how to
// // obtain a package matching this `hash`.
// //
// // Uses the [multihash](https://multiformats.io/multihash/) format.
// .hash = "...",
//
// // When this is provided, the package is found in a directory relative to the
// // build root. In this case the package's hash is irrelevant and therefore not
// // computed. This field and `url` are mutually exclusive.
// .path = "foo",
//
// // When this is set to `true`, a package is declared to be lazily
// // fetched. This makes the dependency only get fetched if it is
// // actually used.
// .lazy = false,
//},
},
// Specifies the set of files and directories that are included in this package.
// Only files and directories listed here are included in the `hash` that
// is computed for this package. Only files listed here will remain on disk
// when using the zig package manager. As a rule of thumb, one should list
// files required for compilation plus any license(s).
// Paths are relative to the build root. Use the empty string (`""`) to refer to
// the build root itself.
// A directory listed here means that all files within, recursively, are included.
.paths = .{
"build.zig",
"build.zig.zon",
"src",
// For example...
//"LICENSE",
//"README.md",
},
}

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{ stdenv
, lib
, zig
, pkg-config
, system
}:
let
target = builtins.replaceStrings ["darwin"] ["macos"] system;
in
stdenv.mkDerivation (finalAttrs: {
pname = "micrograd.zig";
version = "0.0.1";
src = ./.;
nativeBuildInputs = [ zig pkg-config ];
installPhase = ''
runHook preInstall
zig build --global-cache-dir $(pwd)/.cache -Doptimize=ReleaseSafe -Dtarget=${target} --prefix $out install
runHook postInstall
'';
outputs = [ "out" ];
meta = {
description = "Karpathy's micrograd, ported to Ziglang";
homepage = "https://git.oolongtechnologies.io/bogdan/micrograd.zig";
license = lib.licenses.agpl3Only;
platforms = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
};
})

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{
"nodes": {
"flake-compat": {
"flake": false,
"locked": {
"lastModified": 1696426674,
"narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
"owner": "edolstra",
"repo": "flake-compat",
"rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
"type": "github"
},
"original": {
"owner": "edolstra",
"repo": "flake-compat",
"type": "github"
}
},
"flake-utils": {
"inputs": {
"systems": "systems"
},
"locked": {
"lastModified": 1731533236,
"narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
"owner": "numtide",
"repo": "flake-utils",
"rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
"type": "github"
},
"original": {
"owner": "numtide",
"repo": "flake-utils",
"type": "github"
}
},
"nixpkgs": {
"locked": {
"lastModified": 1781007620,
"narHash": "sha256-tvYefqXMF905KCJmVB7vQYYJzLwzOdiOsVn7N6t51wE=",
"owner": "nixos",
"repo": "nixpkgs",
"rev": "d79fdf259deedb11f2ff6208bc83fcca020a6e41",
"type": "github"
},
"original": {
"owner": "nixos",
"ref": "release-26.05",
"repo": "nixpkgs",
"type": "github"
}
},
"nixpkgs-unstable": {
"locked": {
"lastModified": 1780930886,
"narHash": "sha256-rppURzHviaQN131F+nLiLdGfcb0uCd9gGP0E5+iw9MI=",
"owner": "nixos",
"repo": "nixpkgs",
"rev": "8c3cede7ddc26bd659d2d383b5610efbd2c7a16e",
"type": "github"
},
"original": {
"owner": "nixos",
"ref": "nixpkgs-unstable",
"repo": "nixpkgs",
"type": "github"
}
},
"nixpkgs_2": {
"locked": {
"lastModified": 1771043024,
"narHash": "sha256-O1XDr7EWbRp+kHrNNgLWgIrB0/US5wvw9K6RERWAj6I=",
"owner": "NixOS",
"repo": "nixpkgs",
"rev": "3aadb7ca9eac2891d52a9dec199d9580a6e2bf44",
"type": "github"
},
"original": {
"owner": "NixOS",
"ref": "nixos-25.11",
"repo": "nixpkgs",
"type": "github"
}
},
"root": {
"inputs": {
"flake-utils": "flake-utils",
"nixpkgs": "nixpkgs",
"nixpkgs-unstable": "nixpkgs-unstable",
"zig": "zig"
}
},
"systems": {
"locked": {
"lastModified": 1681028828,
"narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
"owner": "nix-systems",
"repo": "default",
"rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
"type": "github"
},
"original": {
"owner": "nix-systems",
"repo": "default",
"type": "github"
}
},
"systems_2": {
"flake": false,
"locked": {
"lastModified": 1681028828,
"narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
"owner": "nix-systems",
"repo": "default",
"rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
"type": "github"
},
"original": {
"owner": "nix-systems",
"repo": "default",
"type": "github"
}
},
"zig": {
"inputs": {
"flake-compat": "flake-compat",
"nixpkgs": "nixpkgs_2",
"systems": "systems_2"
},
"locked": {
"lastModified": 1780967389,
"narHash": "sha256-R+e70r1FSAR3keV6Dexk3hJplDHuTBX51lSKpDBQMkU=",
"owner": "mitchellh",
"repo": "zig-overlay",
"rev": "e303caa9a6cc3a3e2b20a9e339961f418d905794",
"type": "github"
},
"original": {
"owner": "mitchellh",
"repo": "zig-overlay",
"type": "github"
}
}
},
"root": "root",
"version": 7
}

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{
inputs = {
nixpkgs.url = "github:nixos/nixpkgs/release-26.05";
nixpkgs-unstable.url = "github:nixos/nixpkgs/nixpkgs-unstable";
flake-utils.url = "github:numtide/flake-utils";
zig.url = "github:mitchellh/zig-overlay";
};
outputs = {
self,
nixpkgs,
flake-utils,
zig,
...
} @ inputs: let
overlays = [
(final: prev: {
zigpkgs = zig.packages.${prev.system};
zig = zig.packages.${prev.system}."0.16.0";
micrograd = prev.callPackage ./. { };
})
];
in
flake-utils.lib.eachDefaultSystem (
system: let
pkgs = import nixpkgs { inherit overlays system; };
in {
devShells.default = pkgs.mkShell {
nativeBuildInputs = [ pkgs.zig pkgs.zls ];
};
packages.default = pkgs.micrograd;
});
}

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const std = @import("std");
const ExprType = enum {
nop,
unary,
binary,
};
const UnaryType = enum {
tanh,
exp,
relu,
};
const BinaryType = enum {
add,
sub,
mul,
pow,
};
pub fn Value(comptime T: type) type {
if (@typeInfo(T) != .float) {
@compileError("Only floating-point types are supported.");
}
return struct {
const Self = @This();
const Expr = union(ExprType) {
nop: void,
unary: struct {
op: UnaryType,
args: [1]*Self,
},
binary: struct {
op: BinaryType,
args: [2]*Self,
},
};
data: T,
grad: T,
expr: Expr,
var arena: std.heap.ArenaAllocator = undefined;
pub fn init(alloc: std.mem.Allocator) void {
arena = std.heap.ArenaAllocator.init(alloc);
}
pub fn deinit() void {
arena.deinit();
}
pub fn new(value: T) *Self {
return create(value, Expr{ .nop = {} });
}
fn create(value: T, expr: Expr) *Self {
const v = arena.allocator().create(Self) catch unreachable;
v.* = Self{
.data = value,
.grad = 0,
.expr = expr,
};
return v;
}
fn backprop_value(self: *Self) *Self {
switch (self.expr) {
.nop => {},
.unary => |u| {
switch (u.op) {
.tanh => tanh_back(self),
.exp => exp_back(self),
.relu => relu_back(self),
}
},
.binary => |b| {
switch (b.op) {
.add => add_back(self),
.sub => sub_back(self),
.mul => mul_back(self),
.pow => pow_back(self),
}
},
}
}
fn unary(value: T, op: UnaryType, arg0: *Self) *Self {
create(value, Expr{ .unary = .{
.op = op,
.args = [1]*Self{arg0},
} });
}
fn binary(value: T, op: BinaryType, arg0: *Self, arg1: *Self) *Self {
create(value, Expr{
.op = op,
.args = [2]*Self{ arg0, arg1 },
});
}
pub fn add(self: *Self, other: anytype) *Self {
switch (@TypeOf(other)) {
*Self => binary(self.data + other.data, .add, self, other),
else => {
const o = new(other);
return binary(self.data + o.data, .add, self, o);
},
}
}
fn add_back(self: *Self) void {
self.expr.binary.args[0].data += self.grad;
self.expr.binary.args[1].data += self.grad;
}
pub fn sub(self: *Self, other: anytype) *Self {
switch (@TypeOf(other)) {
*Self => binary(self.data - other.data, .sub, self, other),
else => {
const o = new(other);
return binary(self.data - o.data, .sub, self, o);
},
}
}
fn sub_back(self: *Self) void {
self.expr.binary.args[0].data += self.grad;
self.expr.binary.args[1].data -= self.grad;
}
pub fn mul(self: *Self, other: anytype) !void {
switch (@TypeOf(other)) {
*Self => return binary(self.data * other.data, .mul, self, other),
else => {
const o = new(other);
return binary(self.data * o.data, .mul, self, o);
},
}
}
fn mul_back(self: *Self) *Self {
self.expr.binary.args[0].data = self.grad * self.expr.binary.args[1].data;
self.expr.binary.args[1].data = self.grad * self.expr.binary.args[0].data;
}
pub fn div(self: *Self, other: anytype) *Self {
switch (@TypeOf(other)) {
*Self => self.mul(other.pow(-1)),
else => self.mul(new(other).pow(-1)),
}
}
pub fn pow(self: *Self, other: anytype) *Self {
switch (@TypeOf(other)) {
*Self => {
switch (other.expr) {
.nop => binary(std.math.pow(T, self.data, other.data), .pow, self, other),
else => {
@panic("Only Values with nop type are supported as exponents.");
},
}
},
else => |s| {
switch (@typeInfo(s)) {
.int, .float, .comptime_int, .comptime_float => {
const o = new(other);
return binary(std.math.pow(T, self.data, o.data), .pow, self, o);
},
else => {
@compileError("Only integers and floating-point types are supported.");
},
}
},
}
}
fn pow_back(self: *Self) void {
const self_data = self.expr.binary.args[0];
const other_data = self.expr.binary.args[1];
self.expr.binary.args[0].grad += other_data * std.math.pow(T, self_data, other_data - 1) * self.grad;
}
pub fn tanh(self: *Self) *Self {
return unary((@exp(self.data * 2) - 1) / (@exp(self.data * 2) + 1), .tanh, self);
}
fn tanh_back(self: *Self) void {
self.expr.unary.args[0].grad = (1 - self.data * self.data) * self.grad;
}
pub fn exp(self: *Self) *Self {
return unary(@exp(self.data), .exp, self);
}
fn exp_back(self: *Self) void {
self.expr.unary.args[0].grad += @exp(self.expr.unary.args[0].data) * self.grad;
}
pub fn relu(self: *Self) *Self {
return unary(@max(0, self.data), .relu, self);
}
fn relu_back(self: *Self) void {
const grad = if (self.data > 0) self.grad else 0;
self.expr.unary.args[0].grad += grad;
}
};
}

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const std = @import("std");
const print = std.debug.print;
const ValueType = @import("engine.zig").Value;
pub fn main() !void {
var gpa = std.heap.DebugAllocator(.{}){};
const alloc = gpa.allocator();
defer _ = gpa.deinit();
const Value = ValueType(f64);
_ = Value.init(alloc);
defer Value.deinit();
const inputs = [4][3]*Value{
[_]*Value{ Value.new(2), Value.new(4), Value.new(-1) },
[_]*Value{ Value.new(2), Value.new(4), Value.new(-1) },
[_]*Value{ Value.new(2), Value.new(4), Value.new(-1) },
[_]*Value{ Value.new(2), Value.new(4), Value.new(-1) },
};
for (inputs) |row| {
for (row) |val| {
print("{any} ", .{val});
}
print("\n", .{});
}
}

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//! By convention, root.zig is the root source file when making a package.
const std = @import("std");
const Io = std.Io;
/// This is a documentation comment to explain the `printAnotherMessage` function below.
///
/// Accepting an `Io.Writer` instance is a handy way to write reusable code.
pub fn printAnotherMessage(writer: *Io.Writer) Io.Writer.Error!void {
try writer.print("Run `zig build test` to run the tests.\n", .{});
}
pub fn add(a: i32, b: i32) i32 {
return a + b;
}
test "basic add functionality" {
try std.testing.expect(add(3, 7) == 10);
}