How to use Obsidian Chess Engine

Obsidian is a modern, high-performance UCI chess engine that rose very quickly into the top tier of computer chess. It’s written in C/C++, released under GPL-3.0, and uses a neural-network-based evaluation trained from Leela (Lc0) data, which helps explain its fast climb in strength.

What makes Obsidian special (features & strengths)

• Neural-network evaluation: Obsidian evaluates positions using a neural network trained on Lc0-style data. The author emphasizes careful NN training and iterative architecture changes, which have contributed large Elo gains between releases.
• Top-tier playing strength: On public rating lists Obsidian sits among the very strongest engines (in the 3600+ BayesElo range on CCRL listings and similar leaderboards). It competes with other modern top engines in automated championships and rating lists.
• Active development & frequent releases: The project has many releases (with substantial improvements in NN architecture, search tweaks, and multi-threading) and a visible changelog on GitHub. Releases often report measured Elo gains and notes about tradeoffs (speed vs. evaluation complexity).
• Performance tuning and CPU features: The repository supports multiple build targets (native, sse2, ssse3, avx2, avx2-pext, avx512). Some releases have dropped very old CPU variants, so for older processors you may need to build with a lower-level ARCH option.

Quick summary of limitations / notes

• Some prebuilt binaries (or default builds) target modern instruction sets (AVX2/AVX-512/PEXT). If your CPU is older, compile with a compatible ARCH (e.g., sse2 or ssse3) or look for a community build.
• Because evaluation relies on a trained neural net, memory and (depending on network size) RAM usage can be higher than classic handcrafted engines. The author has mentioned tradeoffs between network depth and search speed in release notes/interviews.

How to download and install (step-by-step)

You have two simple options: download prebuilt binaries (if available for your OS) or build from source.

Check the official GitHub releases page (recommended start): go to the Obsidian repo’s Releases and look for a platform build matching your OS (Windows .zip/.exe, Linux .tar.gz or precompiled binary). If a binary is present you can usually just unzip and use it as a UCI engine in a GUI.

Build from source (cross-platform, more control): the repository includes a Makefile and build targets. Typical steps on Linux/macOS (or WSL on Windows.

git clone https://github.com/gab8192/Obsidian cd Obsidian # Example: build with native optimizations (recommended) make -j nopgo build=ARCH

Replace ARCH with one of native, sse2, ssse3, avx2, avx2-pext, avx512 depending on your CPU. The README recommends native for most users.

Windows users who prefer not to build: look for Windows assets on the GitHub Releases page (some releases include zipped executables). If those are not available or your CPU lacks required instruction set, you can either compile with MinGW/MSYS or request a different build from the community.

How to use Obsidian (basic tips)

• Add to a GUI: Obsidian implements the UCI protocol. In any UCI GUI (Arena, SCID vs PC, Cute Chess GUI, ChessBase tools that accept UCI engines), go to Engines → Install New Engine and point to the Obsidian binary. Then set options (threads, hash size).
• Basic UCI commands (for advanced users): after starting the engine you can use setoption name Threads value N, setoption name Hash value 128, ucinewgame, and go depth 20 or go movetime 1000 to force analysis for a fixed depth/time.
• Use as analysis vs playing engine: because Obsidian is very strong and uses an NN eval, it’s excellent for deep analysis. For engine vs engine matches use a harness like Cutechess-cli or the GUI’s match manager. Release notes and the author’s posts often include recommended hashes / thread counts for benchmarking.

Where to read more / follow development

• Official GitHub repo (source, README, releases) — primary source for downloads/build instructions and release details.
• CCRL and other rating lists to see up-to-date Elo comparisons and how Obsidian stacks against other engines.
• Interviews / articles (e.g., Chessdom) for author background and design philosophy.

FAQ: Obsidian Chess Engine

1. What is Obsidian?

Obsidian is a modern, open-source UCI chess engine that uses a neural-network evaluation combined with a fast alpha-beta search. It’s written in C/C++ and available on GitHub under the GPL-3.0 license.

2. How strong is Obsidian compared to other engines?

Obsidian ranks among the strongest engines in the world, reaching top-tier performance on rating lists such as CCRL. Its strength is comparable to other elite engines that use neural-network evaluation.

3. Does Obsidian use a neural network like Leela Chess Zero?

Yes. Obsidian’s evaluation is based on a neural network trained on Lc0-style data. This approach lets the engine “understand” complex positional patterns while keeping search speed very high.

4. What operating systems does Obsidian support?

Obsidian can run on:

• Windows (if a prebuilt binary is available or you compile it yourself)
• Linux
• macOS (usually via source compilation)
  Because it is open-source, it can be built for virtually any platform that supports a C++ compiler.

5. Do I need a GPU to run Obsidian?

No. Obsidian runs entirely on CPU. Its neural network is optimized for CPU inference, unlike Lc0 which often relies on GPU.

6. What CPU features are recommended for best performance?

The engine supports multiple instruction sets: SSE2, SSSE3, AVX2, PEXT, and AVX-512.
For best speed, choose native, avx2, or avx2-pext builds, depending on your processor.

7. How do I download Obsidian?

You can download it from the Releases section of its official GitHub repository. If a precompiled binary is not available for your system, you can compile the engine manually using a simple make command.

8. How do I use Obsidian in a chess GUI?

All you need is a UCI-compatible GUI such as Arena, SCID vs. PC, Cute Chess, or ChessBase.
Go to Install Engine → Choose File → Select the Obsidian binary, then configure Threads and Hash.

9. Can Obsidian play games, or is it only for analysis?

It can do both. You can use it for:

• Deep analysis of positions
• Engine vs. engine matches
• Playing against humans in a GUI
• Tournament tests through Cutechess-cli

10. Is Obsidian free to use?

Yes. It is fully open-source and free under the GPL-3.0 license. You may compile, modify, and redistribute it under the same license.

11. Why won’t the binary run on my computer?

Your CPU may lack the instruction set of the binary you downloaded (for example, AVX2). In that case:

• Download a lower-level version (SSE2/SSSE3), or
• Build the engine from source with a compatible architecture flag.

12. Does Obsidian support Syzygy tablebases?

Most modern engines do, but support varies by build. If Obsidian’s release includes Syzygy integration, you can enable it through your GUI by selecting the tablebase folder. (If not, future builds may add it.)

13. How often is Obsidian updated?

The engine is under active development. The author frequently publishes updates with neural-network improvements, architectural changes, and speed optimizations.

14. Can beginners use Obsidian for study?

Absolutely. Obsidian is excellent for analysis, blunder checking, opening exploration, and endgame study thanks to its strong positional understanding and speed.