▣ fractal_zip

Lossless compression experiments that treat directory trees as first-class data — and, lately, a Hutter Prize submission.

What it is

fractal_zip is a PHP library and CLI for a lossless folder archive format (.fz): a fractal-style inner container (literal bundles, optional PAC lanes, merged-FLAC exploration, …) plus an adaptive outer wrapper that competes gzip‑9, 7‑Zip, zstd, brotli, Arc, and zpaq, keeping the smallest result. It treats directory trees as structured data rather than a concatenated byte stream.

A fair summary: a specialized, integration-first compressor — strongest where the pipeline is owned end to end, folders are structured, and a byte win has been measured. For ubiquitous interchange and predictable latency, zip / zstd / 7z remain sensible defaults. Documented byte wins, with reproduction commands, live in the benchmark ledger inside the repository.

Benchmarks

Best bytes and lifestyle results for every suite case, including enwik9: the benchmarks table.

Try it

• Compress a folder to .fz (web demo, small uploads please)
• Extract a .fz archive
• CLI: ./scripts/fz zip path/to/folder → folder.fz · ./scripts/fz extract archive.fz

fvmem — what the Hutter run gave back

The submission needed a 14 GiB model heap to fit inside a 10 GiB memory cap, which produced fvmem: a compressed in-RAM heap with block eviction, in-place arena reclamation, and physical page release (madvise(MADV_DONTNEED)). It is already in use in other fractal_zip projects — exactly the kind of spillover the competition is good at incentivizing. Source: tools/fractal_compute/fvmem.h.