Fix gpt-oss yarn with truncate argument

[hnyls2002]

To match with https://huggingface.co/openai/gpt-oss-20b/blob/main/config.json#L66

Also related: vllm-project/vllm#28244

[gemini-code-assist]

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[harrisonlimh]

Tested with gpt-oss-120b, and it seems the changed calculations are not creating meaningful differences. I will try with gpt-oss-20b as well.

Impacted variables and tensors with and without truncation:

• correction_range: low: 8, high: 18 vs. low: 8.092779115512402, high: 17.39802450158856
• ramp_func.mean(): 0.5781250596046448 vs. 0.585820198059082
• inv_freq.mean(): 0.0993923768401146 vs. 0.09938869625329971

GPQA eval scores

with truncate

• high:

  • {'chars': 128.6344696969697, 'chars:std': 336.4544423341523, 'score': 0.7973484848484849, 'score:std': 0.40197497255216075}

• medium:

  • {'chars': 267.67108585858585, 'chars:std': 424.53770135412367, 'score': 0.726010101010101, 'score:std': 0.44600385002979953}
  • {'chars': 233.18371212121212, 'chars:std': 402.93011677260085, 'score': 0.7253787878787878, 'score:std': 0.44632320349079807}

• low:

  • {'chars': 150.23800505050505, 'chars:std': 324.1160777618058, 'score': 0.6496212121212122, 'score:std': 0.4770885587429018}
  • {'chars': 145.9671717171717, 'chars:std': 311.72771065301606, 'score': 0.6357323232323232, 'score:std': 0.48122420598922094}

without truncate

• high:

  • {'chars': 138.97095959595958, 'chars:std': 367.965799993336, 'score': 0.7847222222222222, 'score:std': 0.4110149099154914}

• medium:

  • {'chars': 251.08838383838383, 'chars:std': 416.924230715839, 'score': 0.7417929292929293, 'score:std': 0.4376484654879353}
  • {'chars': 230.09911616161617, 'chars:std': 405.0049643033156, 'score': 0.7228535353535354, 'score:std': 0.4475894343932065

• low:

  • {'chars': 146.62815656565655, 'chars:std': 314.83139425447695, 'score': 0.6590909090909091, 'score:std': 0.4740148548775957}
  • {'chars': 136.94444444444446, 'chars:std': 302.62053603939734, 'score': 0.6470959595959596, 'score:std': 0.477873182623323}

[hnyls2002]

/tag-and-rerun-ci

[hlu1]

This fix is consistent with the reference implementation from gpt-oss: https://github.com/openai/gpt-oss/blob/main/gpt_oss/torch/model.py#L98-L107

[hnyls2002]

/tag-and-rerun-ci