IC-315CoT prompting (reasoning + instruction) yields larger relative gains for larger LLMs and harder problems in competitive code generation, with the effect reversing for the most capable models
The paper grid-searches 8 reasoning prompts and 6 instruction prompts across Llama 3.0/3.1 (8B, 70B, 405B) and GPT-4o on CodeContests and TACO. The best reasoning+instruction combination improves pass@100 by +5.0% for Llama 3.0 8B, +9.3% for Llama 3.0 70B, +3.3% for Llama 3.1 8B, and +5.2% for Llama 3.1 70B. On the TACO very-hard split, Llama 3.0 8B pass@100 nearly doubles (2.1% to 3.9%). However, for Llama 3.1 405B, CoT degrades pass@1 by 2.7 points, and for GPT-4o, multi-turn alone degrades pass 1@3 by 4.5 points, indicating the benefit reverses at the top of the scale.
Llama 3.1 405B and GPT-4o evaluated only in small sampling regimes (pass@1, pass 1@3) due to compute constraints; no single prompt combination works best across all models and sample sizes.