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metadata
license: apache-2.0
base_model: Zyphra/Zamba2-7B-instruct
tags:
  - zamba2
  - mamba
  - hybrid
  - compressed
  - hxq
  - helix-substrate
  - vector-quantization
  - 2d-vq
  - 12bit-packing
library_name: transformers
pipeline_tag: text-generation
model-index:
  - name: zamba2-7b-instruct-hxq
    results:
      - task:
          type: text-generation
        dataset:
          name: WikiText-2
          type: wikitext
        metrics:
          - name: Perplexity
            type: perplexity
            value: 3.8454
      - task:
          type: text-generation
        dataset:
          name: HellaSwag
          type: hellaswag
        metrics:
          - name: acc_norm
            type: acc_norm
            value: 0.8106
      - task:
          type: text-generation
        dataset:
          name: ARC-Challenge
          type: ai2_arc
        metrics:
          - name: acc_norm
            type: acc_norm
            value: 0.5811
      - task:
          type: text-generation
        dataset:
          name: ARC-Easy
          type: ai2_arc
        metrics:
          - name: acc_norm
            type: acc_norm
            value: 0.819

Zamba2-7B-Instruct-HXQ

2D Vector Quantization (k=4096) with 12-bit packed indices. 81-layer hybrid Mamba2+Transformer. Faster than dense at 60% less VRAM.

Zamba2-7B-Instruct compressed with HXQ 2D VQ and 12-bit index packing (6 bits/weight). Beats bnb 4-bit NF4 on quality, speed, and requires no calibration data.

Benchmark: Native HelixLinear Inference on RTX 3090

All numbers from a single session, same GPU, same WikiText-2 test set (50 chunks x 512 tokens).

Method PPL Throughput VRAM (load) VRAM (peak) Bits/weight
Dense BF16 4.82 1,446 tok/s 14,032 MB 14,686 MB 16
bnb 8-bit 4.85 515 tok/s 7,831 MB 8,635 MB 8
bnb 4-bit NF4 5.07 1,579 tok/s 5,129 MB 5,904 MB 4
HXQ 12-bit packed 5.02 1,764 tok/s 5,657 MB 6,511 MB 6

Why HXQ wins

  • Faster than dense (1,764 vs 1,446 tok/s) -- fused Triton gather kernel eliminates memory bottleneck
  • 60% less VRAM than dense (5.7 GB vs 14.0 GB)
  • Better quality than bnb 4-bit (5.02 vs 5.07 PPL) at comparable VRAM
  • No calibration data required -- unlike GPTQ, AWQ, or bnb, HXQ compresses from weights alone

Downstream Task Evaluation (lm-eval-harness v0.4.11)

Same GPU (RTX 3090), same harness, same settings. All metrics are acc_norm.

Task Dense BF16 HXQ 2D VQ Delta
HellaSwag 80.79% 81.06% +0.27%
ARC-Challenge 59.39% 58.11% -1.28%
ARC-Easy 83.21% 81.90% -1.31%

Compression preserves task performance within noise. HellaSwag (commonsense reasoning) is slightly better under compression. ARC drops are within 1.3%.

Install and Run

pip install "helix-substrate>=0.3.3"
import helix_substrate  # registers the HXQ quantizer
from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained(
    "EchoLabs33/zamba2-7b-instruct-hxq",
    trust_remote_code=True,
)
tokenizer = AutoTokenizer.from_pretrained(
    "EchoLabs33/zamba2-7b-instruct-hxq",
    trust_remote_code=True,
)

inputs = tokenizer("The capital of France is", return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=32)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))

Note: Tested with transformers>=4.49. mamba-ssm and causal-conv1d recommended for fast Mamba2 inference.

Codec Details

Property Value
Quantization 2D Vector Quantization
Codebook size (k) 4,096
Vector dimension 2 (pairs of adjacent weights)
Bits per weight 6 effective (12-bit packed index / 2 weights)
Index packing 12-bit (3 bytes per 2 indices, lossless)
Compressed modules 213 HelixLinear layers
Exact tensors 573 (norms, embeddings, conv1d, A_log, D, dt_bias)
Sidecar corrections Yes (sparse outlier compensation)
Calibration data None required
HXQ storage 5.7 GB (12-bit packed)
Dense BF16 14.0 GB

Why 2D VQ

Standard scalar VQ assigns one codebook entry per weight. 2D VQ groups pairs of adjacent weights and clusters in R^2 -- the codebook captures the joint distribution. With k=4096 and 12-bit index packing, each pair of weights costs 12 bits = 6 bits per weight. This beats scalar k=256 (8 bits/weight) on both quality and compression.

On Zamba2-7B, 2D VQ k=4096 achieves PPL 3.8454 vs the scalar baseline's higher PPL on this architecture. SSM and hybrid architectures benefit from 2D VQ more than pure Transformers.

Architecture

Zamba2-7B-Instruct is a hybrid architecture:

  • 81 total layers (Mamba2 + shared Transformer)
  • hidden_size=3584, attention_hidden_size=7168, 32 attention heads
  • mamba_d_state=64, mamba_d_conv=4
  • vocab_size=32000

213 linear layers compressed (Mamba projections, attention/MLP, LoRA adapters). Normalization layers, embeddings, conv1d, and Mamba-specific parameters stored at full precision.

Verification

Companion Models

Model Architecture PPL Delta
qwen2.5-14b-instruct-helix Transformer pending
qwen2.5-7b-instruct-helix Transformer +6.34%
qwen2.5-3b-instruct-helix Transformer +0.69%
zamba2-2.7b-instruct-helix Hybrid +6.59%
zamba2-1.2b-helix Hybrid +2.90%
mamba2-1.3b-helix Pure SSM +8.0%
tinyllama-1.1b-helix Transformer +0.78%

Citation

@software{helix_substrate_2026,
  title={Helix Substrate: Universal Weight Compression via HXQ},
  author={EchoLabs},
  year={2026},
  url={https://pypi.org/project/helix-substrate/}
}

License

Apache 2.0 (inherited from Zyphra/Zamba2-7B-instruct).