verification step

**Verification step** is the **phase in speculative decoding where the target model checks draft-proposed tokens and determines which prefix can be safely accepted** - its efficiency and correctness are central to speculative inference performance. **What Is Verification step?** - **Definition**: Target-model evaluation pass that validates candidate tokens from the draft model. - **Decision Output**: Returns accepted token span length and fallback point for resumed decoding. - **Correctness Role**: Ensures final output remains consistent with target-model generation behavior. - **Runtime Cost**: Verification overhead must stay low relative to saved decode steps. **Why Verification step Matters** - **Output Fidelity**: Verification protects quality by preventing unvalidated draft drift. - **Speed Efficiency**: Optimized verification determines practical speculative speedup. - **Stability**: Poor verification handling increases rejection churn and jitter. - **Debugging Clarity**: Accepted versus rejected spans reveal mismatch patterns between models. - **Production Safety**: Verification guarantees are required before deploying speculative modes widely. **How It Is Used in Practice** - **Batch Verification Kernels**: Use efficient parallel checks across proposed token segments. - **Fallback Logic**: Resume standard decoding immediately at first rejected position. - **Telemetry**: Track verification latency and rejection positions to guide tuning. Verification step is **the correctness anchor of speculative decoding pipelines** - fast and reliable verification enables safe acceleration without output corruption.