bigsmall 2.0.1

Lossless neural network weight compression - run any model, no compromises

BigSmall

Run any model. No compromises.

Mistral 7B is 14 GB. Your machine has 8 GB. Today your only option is quantization -- a degraded, worse version of the model. BigSmall changes that.

BigSmall compresses model weights losslessly. Mistral 7B goes from 14 GB to 9 GB. The streaming loader means you never need 9 GB free at once -- it decompresses one layer at a time, directly into VRAM, with a peak RAM footprint of under 2 GB. You run the exact same model. Bit-for-bit identical weights. No quality loss. No accuracy regression. No surprises.

pip install bigsmall

import bigsmall

# Load a compressed model -- same as the original, smaller footprint
state_dict = bigsmall.from_pretrained("wpferrell/mistral-7b-instruct-bigsmall")
model.load_state_dict(state_dict)

# Or stream it layer-by-layer -- runs models bigger than your RAM
with bigsmall.StreamingLoader("wpferrell/mistral-7b-instruct-bigsmall", device="cuda") as loader:
    for layer_idx, tensors in loader.iter_layers():
        # one layer in memory at a time, previous layer already freed
        pass

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The problem with quantization

When a model doesn't fit, the standard answer is quantization. Drop to 4-bit. Use Ollama. It fits now.

But it's not the same model anymore. 4-bit quantization degrades every weight. The outputs are different. Fine-tuning on a quantized model introduces drift. Reproducibility goes out the window. For research, production, or anything where the answer actually matters -- quantization is a compromise you shouldn't have to make.

BigSmall is not quantization. After decompression, every weight is bit-for-bit identical to the original, md5-verified on every tensor. You get the full model. Always.

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What it does

	Quantization (4-bit)	BigSmall
Lossless?	No -- weights degraded	Yes -- bit-identical
Mistral 7B size	~4 GB	9 GB
Peak RAM to load	~4 GB	< 2 GB (streaming)
Inference speed	Slower on some hardware	Native (decompress once)
Fine-tuning safe?	No -- drift from quantized base	Yes -- clean base
Reproducible?	No	Yes

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Benchmarks

All results are lossless -- md5-verified bit-identical reconstruction on every tensor.

Model	Format	Original	Compressed	Ratio
Mistral 7B Instruct v0.3	BF16	14.2 GB	9.3 GB	65.6%
Llama 3.1 8B	BF16	15.0 GB	9.9 GB	65.7%
Qwen 2.5 14B	BF16	28.6 GB	18.8 GB	65.8%
Stable Diffusion 1.5 UNet	FP16	1.72 GB	1.48 GB	85.9%
Stable Diffusion 1.5 VAE	FP32	335 MB	278 MB	83.2%
GPT-2 117M	FP32	548 MB	414 MB	75.5%
GPT-2 117M	BF16	274 MB	165 MB	60.1%

Fine-tune delta compression: 6.95% of source size -- ship fine-tunes as tiny diffs, not full model copies.

Streaming peak RAM: 29.6% lower than full load on GPT-2. On a 70B model the difference is tens of gigabytes.

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Install

pip install bigsmall

Requirements: Python 3.9, 3.10, 3.11, 3.12 | PyTorch 2.0+

Optional extras:

pip install "bigsmall[hf]"        # HuggingFace Hub integration
pip install "bigsmall[diffusion]" # Stable Diffusion support
pip install "bigsmall[vllm]"      # vLLM integration
pip install "bigsmall[all]"       # everything

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HuggingFace integration

import bigsmall

# Compress any HuggingFace model
bigsmall.compress_for_hub("mistralai/Mistral-7B-Instruct-v0.3", output_dir="./mistral_bs")

# Upload to the Hub
bigsmall.upload_to_hub("./mistral_bs", "you/mistral-7b-bigsmall")

# Anyone can load it with one line
state_dict = bigsmall.from_pretrained("you/mistral-7b-bigsmall")

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Pre-compressed models

Ready to use -- no compression step needed:

Model	HuggingFace	Original	Compressed
Mistral 7B Instruct v0.3	wpferrell/mistral-7b-instruct-bigsmall	14.2 GB	9.3 GB
GPT-2 117M	wpferrell/gpt2-bigsmall	548 MB	414 MB

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Streaming loader

The streaming loader lets you run models that don't fit in RAM or VRAM. It decompresses one transformer layer at a time, directly into the target device, and frees the previous layer before loading the next. Peak memory is embeddings + one layer -- typically under 2 GB even for 7B models.

with bigsmall.StreamingLoader("wpferrell/mistral-7b-instruct-bigsmall", device="cuda") as loader:
    print(f"{loader.layer_count()} layers")

    # Load embeddings and non-layer tensors upfront (small)
    base = loader.load_non_layer_tensors()

    # Stream layers one at a time
    for layer_idx, layer_tensors in loader.iter_layers():
        # Previous layer already freed from memory
        # layer_tensors is on device, ready to use
        pass

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vLLM integration

pip install bigsmall[vllm]

import bigsmall

# Serve directly from HuggingFace -- decompresses automatically
bigsmall.vllm_serve("wpferrell/mistral-7b-instruct-bigsmall", port=8000)

Or decompress first and use vLLM normally:

out_dir = bigsmall.vllm_decompress("wpferrell/mistral-7b-instruct-bigsmall")

from vllm import LLM
llm = LLM(model=str(out_dir))
outputs = llm.generate("Tell me about lossless compression.")

vllm_decompress and vllm_serve both accept a HuggingFace repo ID, a local directory of .bs shards, or a single .bs file.

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CLI

bigsmall compress model.safetensors                   # balanced (default)
bigsmall compress model.safetensors --storage         # maximum compression
bigsmall compress model.safetensors --inference       # fastest load
bigsmall decompress model.bs -o model.safetensors
bigsmall info model.bs
bigsmall verify model.bs

# Fine-tune delta
bigsmall compress finetune.safetensors --base base.safetensors -o delta.bs
bigsmall decompress delta.bs --base base.safetensors -o reconstructed.safetensors

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Format support

Format	Ratio	Notes
BF16	60-66%	LLMs (Mistral, Llama, Qwen)
FP32	75-83%	GPT-2, SD VAE, research models
FP16	77-86%	SD UNet, half-precision models
FP8	71-72%	Quantization-aware models
FP4	~30%	Extreme compression

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Comparison

Tool	BF16 Ratio	FP32 Ratio	Inference Overhead	Hardware	Venue
ZipNN	67%	83%	None (load-time only)	CPU	arXiv '24
DFloat11	~70%	BF16 only	~2x at batch=1	CUDA	NeurIPS '25
ZipServ	~70%	BF16 only	1.22x faster	GDDR GPU	ASPLOS '26
Unweight	~80%*	BF16 only	None	H100/H200	Tech Report
BigSmall	65.6%	75.5%	None	CPU + any GPU	—

Lower ratio = better compression. BigSmall BF16 ratio measured on Mistral 7B, FP32 on GPT-2, md5 verified lossless. *Unweight compresses MLP weights only (~20% total model size reduction).

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Paper

BigSmall: Lossless Neural Network Weight Compression at the Joint Entropy Floor

Full technical paper covering the joint entropy floor proof, per-tensor arithmetic codec, streaming loader architecture, and benchmarks across all five float formats. Preprint — arXiv submission in progress.

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License

Apache 2.0