Show HN: Sameshi – a ~1200 Elo chess engine that fits within 2KB

80•datavorous_•2h ago

I made a chess engine today, and made it fit within 2KB. I used a variant of MinMax called Negamax, with alpha beta pruning. For the board representation I have used a 120-cell "mailbox". I managed to squeeze in checkmate/stalemate in there, after trimming out some edge cases.

I am a great fan of demoscene (computer art subculture) since middle school, and hence it was a ritual i had to perform.

For estimating the Elo, I measured 240 automated games against Stockfish Elo levels (1320 to 1600) under fixed depth-5 and some constrained rules, using equal color distribution.

Then converted pooled win/draw/loss scores to Elo through some standard logistic formula with binomial 95% confidence interval.

Comments

chvid•2h ago

Cool that you could keep it under 2k but it would nice to have a readable version of the source code.

Do you work with it like this or do you have some sort of script you apply to get it down to a single line, single letter variable names?

noutella•2h ago

What you’re describing is the typical output / function of a minifier

alansaber•2h ago

The real fun would be reverse-engineering the minified code (there are loads of tools to do this for chrome extensions)

TZubiri•1h ago

not lossless

GeertB•2h ago

How did you handle games where Stockfish would castle or promote?

datavorous_•2h ago

i forced stockfish to play only non castling, non en passant, non promotion moves by filtering legal moves and passing only those as root_moves

also removed castling/EP rights from FEN

lekevicius•2h ago

Do you think it would be possible to achieve 1:1 ELO:bytes? Even smaller, but can be less smart.

datavorous_•1h ago

maybe for very low ratings it's plausible? 1 elo per byte might happen in a tiny range but at a useful strength it would break fast, that's what i think

iterance•45m ago

What's the snallest possible program that accepts a chess board state and prints any legal move? True randomness may only have a couple hundred ELO, but then, that's pretty big for golf

esafak•44m ago

That's an awesome code golf challenge

TZubiri•1h ago

Codex or Claude Code?

datavorous_•1h ago

none.

scribbling long enough on a piece of paper is more enjoyable than prompting.

semi-extrinsic•53m ago

a thousand times this.

haute_cuisine•1h ago

This is amazing! Thanks for sharing. What would be the elo gain for 4KB engine?

P.S. I assume 1200 elo in chess com scale (not lichess / fide elo) and bullet chess variant?

grumpopotamus•1h ago

There is a TCEC category for 4k engines. The top ones are ~3000 Elo.

sigmoid10•1h ago

It's wild to think that 4096 bytes are sufficient to play chess on a level beyond anything humans ever achieved. Makes you think what other difficult tasks are out there that take even highly gifted humans years or decades to master, but a superior algorithm would more or less fit into one of those big QR code formats.

These things always make me think back to Westworld season 2, where the finale revealed that human minds are much simpler than they themselves believe and fit completely into an algorithm that could be printed in an average book.

kevmo314•1h ago

The core search algorithm is very simple though. 4KB engines may not run that fast if they do exhaustive search, but they’ll be quite accurate.

According to TCEC the time control is 30 mins + 3 sec, that’s a lot of compute!

sigmoid10•59m ago

If you look at the current winner [1], it does a lot more than just brute force tree search. The space state for chess is simply too big to cover without good heuristics. Deep Blue may have been a pure brute force approach to beat Kasparov after Deep Thought failed using the same core algorithm, but modern chess engines search far deeper on the tree with far fewer nodes than Deep Blue ever could thanks to better heuristics.

[1] https://github.com/MinusKelvin/ice4

kevmo314•44m ago

I'm not suggesting that it's only brute force tree search, just that it's not very complicated to develop a theoretically perfect chess engine in direct response to the parent

> It's wild to think that 4096 bytes are sufficient to play chess on a level beyond anything humans ever achieved.

vunderba•1h ago

Well, one of the most fundamental algorithms for building a chess AI is minimax [1] (or variants like negamax), and that’s been around for close to a century. The key difference is that as compute power and available RAM have grown, it’s become possible to search much deeper and evaluate far more plies.

So while 4k is still very impressive for the code base, it comes with a significantly larger runtime footprint.

[1] - https://en.wikipedia.org/wiki/Minimax

falsaberN1•1h ago

Oh my god the source is so tiny! It's really hard to parse because of it being minified but I love it to bits.

burstw0w•1h ago

Good job! I love how you obfuscated your code, really in a spirit of FOSS!

y-curious•1h ago

Coworker: “hey if you have a second, I have a one-liner PR open”

The PR:

datavorous_•1h ago

Oh well, the file initially looked like https://github.com/datavorous/sameshi/blob/7ab4e47144f96becd...

It is hideous now!

tromp•46m ago

https://www.chessprogramming.org/Toledo is a family a moderately strong tiny chess programs.

jll29•31m ago

Cool project. You could also use the front-end of GNU chess to save some lines, and implement only a back-end.

Bug report:

    a b c d e f g h
  8 r n b q k b n r 8
  7 . . p p p p p p 7
  6 . p . . . . . . 6
  5 p . . . . . . . 5
  4 P . . P P . . . 4
  3 . . . . . . . . 3
  2 . P P . . P P P 2
  1 R N B Q K B N R 1
    a b c d e f g h
  move: b2b3
  ai: b6b4

The pawn is not permitted to move two fields after it has already beeen moved once before: b6b4 isn't a valid move after b7b6. (First moving two fields, and then one would have been okay, in contrast.)

datavorous_•25m ago

Thanks for pointing it out! I will try to patch it.

Appreciate you taking the time to test it.

dfc•25m ago

How many games did you have to throw away because stockfish wanted to castle? Or did you force stockfish to not castle? Castling seems like such a frequent move it is hard to draw any conclusions about the strength of an engine that does not support it.

datavorous_•12m ago

zero games were thrown away for castling, because i forced stockfish not to castle (and not to play en passant/promotion) by filtering legal moves and only giving those filtered moves via root_moves

so every game stayed in the same no castling variant

and you're right, this rating is for that constrained variant, not full chess.

oh_my_goodness•22m ago

If you ever spent much time at a chess club, you've seen why 2kB is a really disturbing number.

jqr-•12m ago

I have not. Can you please tell me why?

sireat•15m ago

This is very cool and having stalemate is nice, however how much space would it take to implement the full ruleset?

As you write: not implemented: castling, en passant, promotion, repetition, 50-move rule - those are all required to call the game being played modern chess.

I could see an argument for skipping repetition and 50-move rule for tiny engines, but you do need castling, en pessant and promotion for pretty much any serious play.

https://en.wikipedia.org/wiki/Video_Chess fit in 4k and supported fuller ruleset in 1980 did it not?

So I would ask what is the smallest fully UCI (https://www.chessprogramming.org/UCI) compliant engine available currently?

This would be a fun goal to beat - make something tiny that supports full ruleset.

PS my first chess computer in early 1980s was this: https://www.ismenio.com/chess_fidelity_cc3.html - it also supported castling, en pessant, not sure about 50 move rule.

l674•9m ago

If anyone is curious, the most common tool I've seen for ELO estimation among engine developers is cutechess [1], which uses SPRT [2]. Or ordo [3], haven't used this myself though

[1] https://cutechess.com/

[2] https://www.chessprogramming.org/Sequential_Probability_Rati...

[3] https://github.com/michiguel/Ordo

Ooh.directory: a place to find good blogs that interest you

My smart sleep mask broadcasts users' brainwaves to an open MQTT broker

Show HN: Sameshi – a ~1200 Elo chess engine that fits within 2KB

Zig – io_uring and Grand Central Dispatch std.Io implementations landed

Platforms bend over backward to help DHS censor ICE critics, advocates say

Shades of Halftone

Vim 9.2 Released

Show HN: I spent 3 years reverse-engineering a 40 yo stock market sim from 1986

A Review of M Disc Archival Capability. With long term testing results

Show HN: SQL-tap – Real-time SQL traffic viewer for PostgreSQL and MySQL

How many registers does an x86-64 CPU have? (2020)

Ars Technica makes up quotes from Matplotlib maintainer; pulls story

Code Storage by the Pierre Computer Company

Babylon 5 is now free to watch on YouTube

Homeland Security has sent out subpoenas to identify ICE critics

What color are your bits? (2004)

The Sling: Humanity's Forgotten Power

The mathematics of compression in database systems

Understanding the Go Compiler: The Linker

The World of Harmonics – With a Coffee, Guitar and Synth

Sound and Practical Points-To Analysis for Incomplete C Programs [pdf]

Show HN: Data Engineering Book – An open source, community-driven guide

How the Little Guy Moved

Building a TUI is easy now

Cogram (YC W22) – Hiring former technical founders

Common Lisp Screenshots: today's CL applications in action

Font Rendering from First Principles

GPT-5.2 derives a new result in theoretical physics

NPMX – a fast, modern browser for the NPM registry

YouTube as Storage

Ooh.directory: a place to find good blogs that interest you

My smart sleep mask broadcasts users' brainwaves to an open MQTT broker

Show HN: Sameshi – a ~1200 Elo chess engine that fits within 2KB

Zig – io_uring and Grand Central Dispatch std.Io implementations landed

Platforms bend over backward to help DHS censor ICE critics, advocates say

Shades of Halftone

Vim 9.2 Released

Show HN: I spent 3 years reverse-engineering a 40 yo stock market sim from 1986

A Review of M Disc Archival Capability. With long term testing results

Show HN: SQL-tap – Real-time SQL traffic viewer for PostgreSQL and MySQL

How many registers does an x86-64 CPU have? (2020)

Ars Technica makes up quotes from Matplotlib maintainer; pulls story

Code Storage by the Pierre Computer Company

Babylon 5 is now free to watch on YouTube

Homeland Security has sent out subpoenas to identify ICE critics

What color are your bits? (2004)

The Sling: Humanity's Forgotten Power

The mathematics of compression in database systems

Understanding the Go Compiler: The Linker

The World of Harmonics – With a Coffee, Guitar and Synth

Sound and Practical Points-To Analysis for Incomplete C Programs [pdf]

Show HN: Data Engineering Book – An open source, community-driven guide

How the Little Guy Moved

Building a TUI is easy now

Cogram (YC W22) – Hiring former technical founders

Common Lisp Screenshots: today's CL applications in action

Font Rendering from First Principles

GPT-5.2 derives a new result in theoretical physics

NPMX – a fast, modern browser for the NPM registry

YouTube as Storage

Show HN: Sameshi – a ~1200 Elo chess engine that fits within 2KB

Comments