nordisk/znippy-zoomies

lbunzip2 — guide

Class: guide · Function: lbunzip2. Build, run, tune. Shape in lbunzip2-design.md; why in lbunzip2-reasoning.md.

Build

CARGO_TARGET_DIR=/mnt/work4t/cargo-target/zoomies cargo build --release -p lbzip2

Binary lands at target/release/lbunzip2.

Run

lbunzip2 planet.osm.bz2               # → planet.osm  (strips .bz2)
lbunzip2 in.bz2 out                   # explicit output path

Reads anything bzip2 / lbzip2 / pbzip2 wrote (stock format, single-stream or pbzip2-style concatenated). Watch htop: cores should sit near-flat; the block scan is the only serial-ish work and it is itself fanned across cores.

Tune

• LBZIP2_THREADS=N pins worker count. LBZIP2_THREADS=1 forces the single-worker _st bench row and still streams the whole file (segments are floored at 2, decoded one at a time — see the design's "segmentation floor"). Unset ⇒ physical core count.

Library twins

The CLI is streaming; for in-memory or Read-trait use reach for the library readers (lbzip2::parallel::decompress_parallel, StreamingBz2Read, ParallelBz2Read) — documented in lbzip2-readers-design.md / -guide.

Bench

HEAVY only (no smoke): nornir bench run znippy-zoomies then nornir docs book znippy-zoomies fills the README A/B/C mashup. The _st single-core row (LBZIP2_THREADS=1) races stock serial bzip2; the all-core row races lbzip2/pbzip2. See decompressors-guide.md.