{
  "skill": "interview-cheatsheet",
  "source": "docs/tutorials/reasoning_models_tutorial.md",
  "output": "docs/tutorials/reasoning_models_tutorial.html",
  "topic": "Reasoning Models (o1 / R1 / Test-Time Compute / PRM / GRPO)",
  "effort": "max",
  "byline": "Ruofeng Yang (杨若峰), Shanghai Jiao Tong University",
  "reviewer": "codex gpt-5.5 xhigh, fresh thread per round",
  "math_code_review": {
    "verdict": "PASS (with length WARN)",
    "rounds": [
      {
        "run": "1-3 (subagent)",
        "verdict": "FAIL→FAIL→PASS",
        "notes": "Multiple rounds of cross-model codex review run by writing agent before continuation hung."
      },
      {
        "run": 4,
        "verdict": "FAIL → fixed",
        "thread_id": "019e3f44-8186-7c32-8e73-b1244b9994b2",
        "reviewer": "main-session DIY backfill",
        "issues_caught": [
          "Q22 wrong claim: InstructGPT RM gives 'dense token-level reward' (actual: response-level scalar preference reward; token-level advantage comes from critic + GAE + KL)",
          "Snell 2024 4× mischaracterization in TL;DR (should be compute-optimal test-time scaling vs best-of-N baseline, not '比线性扩参数有效 4×')",
          "Math-Shepherd labeled as 'MCTS rollout' (actual: Monte Carlo completion rollouts, not MCTS tree search) — fixed in 3 places",
          "extract_answer LaTeX parser broken on nested `\\boxed{\\frac{1}{2}}` (truncated to `\\frac{1`)",
          "grpo_loss did not enforce detach on log_probs_old / log_probs_ref",
          "Q11 + comment claimed 'std=0 时 loss=0' — actual: PG term zeroes, KL term remains",
          "prm_beam_search edge case: empty new_beams → max() ValueError",
          "7 callout-list collisions (callouts immediately followed by lists with no blank line)",
          "Length 1254 lines (target 800-1200) — accepted as content-dense WARN"
        ],
        "fixes_applied": [
          "Q22 rewritten: clarified InstructGPT RM is response-level scalar; token-level signal comes from critic + GAE + KL",
          "TL;DR Snell 2024 description rewritten: compute-optimal scaling vs best-of-N baseline yields >4× efficiency; FLOPs-matched setting yields up to 14× larger model match",
          "Math-Shepherd description updated in §0 TL;DR + Q4 to Monte Carlo completion rollouts with arXiv 2312.08935 citation",
          "Rewrote extract_answer with balanced-brace _extract_braced() helper to handle nested LaTeX",
          "grpo_loss: added defensive detach() calls on log_probs_old/ref + updated docstring",
          "Q11 + grpo_loss comment updated: PG=0 when std=0, but KL penalty term remains",
          "prm_beam_search: added empty new_beams guard + fallback return",
          "Inserted blank lines after 7 callout headers to avoid markdown blockquote-list ambiguity"
        ],
        "issues_deferred_as_low": [
          "Appendix temporal order (2022-03 listed before 2022-05) — cosmetic",
          "R1-Zero 'aha moment' Figure 3 vs Table 3 — cosmetic citation nit",
          "o3 ARC-AGI 75.7/87.5 caveat (production o3 differs from ARC Prize preview system)"
        ]
      }
    ]
  },
  "render_review": {
    "verdict": "PASS",
    "rounds": [
      {
        "run": 1,
        "verdict": "PASS",
        "thread_id": "019e3f69-5d50-7eb3-8c53-fdc504a2db64",
        "reviewer": "codex gpt-5.5 xhigh, fresh thread (main session)",
        "notes": "13/13 functional checks pass. 45 headings, 11 code blocks, 5 tables, 18 callouts (0 raw blockquotes remaining — all callout-list collisions fixed), 25 details blocks. Source SHA256 549e2f7e241c matches."
      }
    ]
  },
  "summary": "Reasoning Models tutorial: subagent did 3 rounds before hang, main-session DIY did 1 substantive round catching 9 errors (Q22 RM semantics, Snell 4× description, Math-Shepherd MCTS→MC fix, extract_answer parser, grpo_loss detach, prm_beam edge case, KL penalty edge case, 7 callout-list spacings). Final 13/13 render PASS. 1254 lines content-dense (WARN).",
  "rendered_at": "2026-05-19",
  "notes": "Subagent was killed during continuation due to codex MCP concurrency hang. Substantive review + fixes + render + render review completed in main session DIY."
}