> **DRAFT — DO NOT UPLOAD.** Strip this block before publishing. Publishes at V4-REL on Will's
> word (V4_DOCS_SPEC.md Deliverable 8/9). Every number is traced in V4_DOCS_REPORT.md appendix A
> (claims ledger). Supersedes _v315/PUBLIC_DRAFTS/hf_card_README.md (the "Coming in 3.15" block
> there is obsolete — 3.15 shipped 2026-06-11, and this card is the 4.0 story).

# BigSmall — Lossless AI Model Compression

**Lossless AI model compression — ~34% smaller with bit-identical weights; the autopilot profiles your machine, picks the highest fidelity that runs, and streams models bigger than your RAM.**

```bash
pip install bigsmall          # CLI + compression/decompression
pip install bigsmall[torch]   # add this for model loading (from_pretrained)
```

Every model on this page is a real measurement: a 14 GB Mistral-7B is 8.9 GB as a `.bs`, a
29.5 GB Qwen2.5-14B-Instruct is 19.5 GB — and after decompression **every weight is bit-for-bit
identical to the original** (md5 verified per tensor on decompress).

- **Not quantization.** Nothing is rounded; the model's behaviour cannot change.
- **Not pruning, not approximation.** The same idea as ZIP for text, tuned for the statistics
  of trained BF16 weights.
- **Fine-tunes ship as deltas.** A >=7B official instruct tune stored against its public base
  measures 34–50% of the full model. Delta size is pair-dependent (measured range: under 1% for
  the best >=7B SFT pairs, up to ~61% for small-model full tunes) — the docs carry the full
  measured table.

## Using a pre-compressed model

```python
from transformers import AutoModelForCausalLM

model = AutoModelForCausalLM.from_pretrained(
    "wpferrell/phi-3.5-mini-instruct-bigsmall"
)
```

BigSmall decompresses transparently on load. Prefer the CLI? Download the repo and run
`bigsmall decompress model-00001-of-00002.bs -o model.safetensors`.

## New in 4.0 — the autopilot release

Three commands replace every settings decision:

```bash
bigsmall profile     # once: ~10s hardware probe (GPU read via NVML only, never touched)
bigsmall plan f.bs   # one sentence: what would run, where, how faithfully, how fast
bigsmall run f.bs    # do it
```

The rule is *highest fidelity at usable speed*, and the honesty rules are enforced by the test
suite: anything below bit-exact is announced before it happens, never silently.

- **The Ferrell Duo (`.bsd`)** — one file. Two models: the fast one and the real one. A
  lossy-INT4 fast member (load by reading ~21% of raw bytes) *and* the lossless residual that
  reconstructs the original bits; the bit-exact gate runs before the file may exist. Measured
  cost: ~2.9 pp of raw over lossless-only. To our knowledge (as of 2026-06-12) the only shipped
  LLM-weights format whose top tier is the bit-exact original — adjacent art (MatQuant,
  Any-Precision LLM, audio hybrid formats) credited in the repo's comparison page.
- **Streaming executor** — run models bigger than your RAM with a bounded, promised, measured
  resident set. Receipt at 7B: Qwen2.5-7B (14.2 GB raw, 65.95% compressed) streamed forward
  **bit-exact** vs the fully-loaded model (identical logits sha256) in ~2.5 GB of hot state.
- **FP8-native lossless** — a real fp8 release (Qwen3-0.6B-FP8) compressed to **0.829 of its
  fp8 weight bytes**, 507/507 tensors bit-exact.
- **`bigsmall xray`** — checkpoint forensics with a "looks untrained" trap that catches
  silently-randomized loads; works on bf16 and fp8.

## Honest numbers

The lossless floor for trained BF16 weights is real and measured: across 4,143 weight matrices
in 8 architectures the per-tensor entropy floor is flat (CV ~ 0), and trained mantissa/sign bits
are coder-equivalent to matched random controls — training only writes the exponent. BigSmall
codes at that wall. Head-to-head under the same accounting, BigSmall codes below DFloat11's
bound on **every layer type of every model measured** (+0.45–0.55 pp model-level, +12–18 pp on
norm scales) — see `docs/dfloat11.md` in the source repo; the full landscape (DFloat11, ZipNN,
ZipServ, Unweight, quantization, and the rest) is one honest page at `docs/comparison.md`.

## Links

- **PyPI** — https://pypi.org/project/bigsmall/
- **Source** — https://github.com/wpferrell/Bigsmall
- **Paper / DOI** — https://doi.org/10.5281/zenodo.20279247
- **Ferrell Duo paper** — https://doi.org/10.5281/zenodo.20673133 (the dual-fidelity format: method, premium history, receipts)
- **License** — Elastic License 2.0 (free for personal, research, and internal commercial use);
  model weights in `.bs` format keep the license of the original model.
- **Contact** — wpferrell@gmail.com