Skip to content

Bounded-memory LZMA encoders (xz/lzma2/.lzma): O(dict_size), not O(input) #101

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
MagicalTux merged 3 commits into from
Jun 15, 2026
Merged

Bounded-memory LZMA encoders (xz/lzma2/.lzma): O(dict_size), not O(input) #101

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
79748b4
lzma/xz/lzma2: bounded-memory sliding-window streaming encoders
MagicalTux Jun 15, 2026
73957f8
lzma/lzma2: early-commit long matches in the optimal parser
MagicalTux Jun 15, 2026
cc42fd9
docs: changelog for bounded-memory LZMA encoders; demote private doc …
MagicalTux Jun 15, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 9 additions & 4 deletions CHANGELOG.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -84,10 +84,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
linear-time SA-IS suffix-array construction.
- **mtf** encode ~2.3× faster (single-pass scan-and-shift); **rangecoder**
encode/decode ~+15% (tightened hot loops).

Note: the xz/lzma2 and zstd encoders now buffer the whole input to drive a
single continuous match-finder (same memory profile the `.lzma` path already
had); higher levels trade encode time for ratio, decode speed is unchanged.
- **Bounded-memory LZMA encoders.** The `xz`, raw `lzma2`, and `.lzma`
encoders now stream with a sliding window whose match finder, history, and
hash chains are all `O(dict_size)` (default 4 MiB) instead of buffering the
whole input — peak memory is now independent of input length (≈45 MB RSS
encoding a 600 MB file; previously O(input) and OOM-prone). The continuous
dictionary, and therefore the ratio, is unchanged (matches already could not
reach past `dict_size`): `xz`/`.lzma` on the 2.9 MB corpus stay within 0.03%.
Output continues to decode byte-for-byte with system `xz`. (`zstd` already
streamed within its bounded window.)

## [0.6.3](https://github.com/KarpelesLab/compcol/compare/v0.6.2...v0.6.3) - 2026-06-15

Expand Down
Loading
Loading