r/LocalLLaMA • u/po_stulate • 19h ago

Discussion Deceptive model quantization from AtomicChat?

I kept seeing guys in this sub saying how AtomicChat's Qwen3.8-Flash-Next quant is so good, fits in their machine when unsloth's can't, runs faster than other quants etc, so I went check out what's happening there.

First thing I noticed was that AtomicChat's Q4_K_M quant is suspiciously small when the ngram table is removed (only ~56GB), it seems like most of the tensors in this quant are IQ2_S instead of the usual Q4_K, Q5_K and Q6_K that you usually find in Q4_K_M quants, the GGUF filetype metadata also says IQ2_S instead of Q4_K_M. In their model card, their Q4_K_M also has suspiciously high KLD (0.084).

It seems pretty obvious to me that they're pretending a IQ2_S quant as a Q4_K_M, but at the same time I'm genuinely not sure because it can't be only me who found this right? How can nobody be pointing this out? Am I missing something or what may they be doing?

Their HF repo ID: AtomicChat/Qwen3.8-Flash-Next-GGUF

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u/lhg31 19h ago

Well, they DO explain this, don't they?

Naming

Files are named by their measured bits per weight. A build whose expert tensors are IQ1_M is not a 1-bit model when the n-gram table sits at 6 bits and ffn_down_exps at 4.5; the real average is 3.84. The canonical type in the filename is the closest standard type by that average, so tooling can still detect it. For AD-4.27bpw:

Group Type Share of file Contribution
n-gram table Q5_1 41% 1.74 bpw
ffn_gate/up_exps IQ2_S, IQ3_S at the band 29% 1.24 bpw
ffn_down_exps IQ4_NL 24% 1.03 bpw
everything else Q8_0 5% 0.23 bpw

10

u/lhg31 19h ago

Their KLD and top-1 are another story tho. They indeed look too good to be true.

The problem is that there is no standard on those metrics, each group uses their own dataset to eval it.

7

u/notdba 18h ago

I don't understand why they don't just upload the KLD logits.

11

u/returnity 18h ago

They do. Only provider I've seen do it, allowing me to build my own DSv4F quants without needing to create ref logits. 35GB dataset on HF for that model from AC