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You’ve reached the website of Cosmo, a computer person with an interest in artificial intelligence & low-level programming, particularly deep learning and chess engines.

I care very much about the correctness and performance of software, and hope that you do too. I have a continuing fondness for the Rust programming language, and use it extensively in my projects. I work on web services and command-line tools, accidentally standardise data formats, and reïmplement the occasional ML paper.

You may also enjoy the works of my most wonderful friends, at sialia.dev, ettolrach.com, and typ·dev.

• Talks
• Library
• External content

• A few optimisers, and Schedule-Free NNUE
  Note on a few different optimisers
• MCTS & neural policies
  Thoughts on neural policies in chess engines
• Dead and forgotten
  A timeline of Type Help
• The three kinds of uncertainty
  Uncertainty, and magical crises of identity
• AlphaZero, RL, and SPSA
  On the training objective of AlphaZero, and the use of SPSA to directly optimise win-rate in lc0.
• Better activation functions for NNUE
  Results from Swish and SwiGLU in NNUE.
• Chess networks use a Gated Nonlinear Unit
  In which I analogise pairwise multiplication to the Gated Linear Unit.
• Training dynamics of target weighting
  Does it matter whether you predict the true future, or a stronger version of yourself?
• Deep NNUE
  Important architectural improvements in Viridithas 14.
• More experimentation in NNUE
  King buckets, output buckets, and Elo scaling with network size.
• Experimenting with NNUE configurations
  Results from activation functions, learning rates, and batch sizes.
• The advanced NNUE program
  A statement of general intent.
• NNUE performance improvements
  How to make NNs run fast in chess engines.
• Contra “Grandmaster-Level Chess Without Search”
  A critique of DeepMind's searchless chess paper, with comparison to Lc0.
• An overview of computer chess techniques
  Alpha-beta, PVS, iterative deepening, move ordering, search reductions, etc.
• and more at the Sitemap.