Qwen3.5-4B — GGUF Q2_K_XL refined with GSQ
GGUF Q2_K_XL checkpoint of Qwen/Qwen3.5-4B
in which the discrete grid assignments have been refined with GSQ
(Gumbel-Softmax Quantization), starting from the public Unsloth GGUF
initialization and projected back into the same K-Quant format.
The optimized file runs unchanged on llama.cpp / Ollama and is a
drop-in replacement for the corresponding standard GGUF checkpoint.
Quantization details
- Base model:
Qwen/Qwen3.5-4B
- Starting point: Unsloth GGUF
UD-Q2_K_XL
- Released quantization:
Q2_K_XL
- Format: GGUF K-Quant
- Pipeline: Unsloth GGUF init → GSQ Gumbel-Softmax refinement → re-pack into the same format
- Runtime:
llama.cpp, ollama, LM Studio, anything that consumes GGUF
Storage layout
This file is bit-for-bit standard GGUF Q2_K. GSQ only changes the
values of the quantized weights by relearning the discrete grid assignments
inside each K-Quant block.
As a result:
- The file size matches the corresponding upstream Q2_K_XL file for the same model.
- Any
llama.cpp / ollama build that loads a regular Qwen3.5-4B Q2_K_XL GGUF
should load this file with zero changes.
- The Hugging Face UI reports the GGUF block type, e.g.
Q2_K_XL, rather than
per-tensor dtypes. This refers to the on-disk K-Quant encoding, not the
precision of any optimizer state used during GSQ refinement.
Evaluation
We compare the GSQ-refined checkpoint against the Unsloth UD-Q2_K_XL
checkpoint used as initialization.
Evaluation notes
All evaluations are zeroshot. The Unsloth UD-Q2_K_XL model was evaluated with thinking disabled on all
tasks, because its thinking mode was found to be broken and produced worse
results.
For the GSQ-refined model:
- AIME 25 and GPQA Diamond were evaluated with thinking enabled.
- IFEval, GSM8K, and MMLU-Pro were evaluated with thinking disabled.
Token Efficiency
For MMLU-Pro, both models were evaluated with a maximum output budget of 32K
tokens.
- The Unsloth model consumed 55.32M output tokens in total.
- The GSQ-refined model consumed 41.82M output tokens in total.
Usage with llama.cpp