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Can gzip be a language model?

by Nathan Barrynathan.rspublished

Hraness wrote this summary from a saved copy of the source. Quotations are taken word for word from the source.

gist

Nathan Barry shows that gzip can act as a crude language model when a corpus is loaded into DEFLATE’s sliding window and candidate continuations are ranked by compressed length. Because compression rewards byte sequences resembling recent context, beam search can produce Shakespeare-like fragments without neural weights or training. The output remains incoherent and quantized, but the experiment makes compression–prediction equivalence tangible and offers a tiny, inspectable generative model.

ideas

  • Compression hides prediction. The bits a compressor spends encode an implicit probability model: expected continuations cost less.
  • DEFLATE supplies the memory. Its 32 KiB sliding window makes corpus-like byte sequences cheap through back-references.
  • Beam search makes generation viable. Looking ahead across spans avoids the ties and quantization noise of one-byte greedy scoring.
  • Context must stay bounded. Keeping only a recent tail limits verbatim loops that would otherwise dominate the search.

quotes

“every prediction model is inherently a compressor, and all compression algorithms are prediction models.”

Nathan Barry, stating the compression–prediction equivalence.

“A continuation that gzip “expected”, because it echoes text already in its window, compresses to almost nothing.”

Nathan Barry, explaining how DEFLATE scores candidates.