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Polestar: Drift-Aware Cache Calibration and Token Commitment for Efficient Inference of Diffusion LLMs
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Polestar is a training-free dLLM inference framework that uses KL-based token representation drift to drive sparse KV-cache refreshes (Polestar-Cache) and drift-aware early token commitment (Polestar-Commit), improving the accuracy-throughput Pareto frontier.
Problem
Diffusion LLM inference is slowed by bidirectional attention, which prevents standard KV-cache reuse, and by static confidence thresholds for parallel decoding that trade off accuracy against parallelism.
Approach
Token representation drift (KL divergence of a token's attention distribution across consecutive steps) is used as a unified signal: to pick which cached KV positions (clustered, quantized hidden states) to refresh sparsely, and to detect sharp drift spikes that signal commit-ready tokens in the current and suffix blocks.
Key results
- On GSM8K (256 gen length) with LLaDA-8B-Instruct, Polestar reaches 78.33% accuracy, 3.67 TPF and 87.57 TPS (13.3x over baseline), versus 79.30% and 6.58 TPS for the baseline.
- Polestar improves accuracy by up to 10.73% over KV-caching baselines and achieves up to 20.5x speedup over baseline.
- On ParallelBench-easy, Polestar achieves 2.43 TPF and 82.41 TPS (7.8x) with 74.18% accuracy.
Surprising findings
- Lowering the static confidence threshold to 0.7 raises TPF to 3.71 but causes a large accuracy drop, showing confidence-only scaling is suboptimal.
- Polestar improves accuracy over the full-recomputation baseline on some settings (e.g., GSM8K-512, HumanEval-512) while also increasing throughput.
Limitations
- Gains are highest on GSM8K/HumanEval; on some settings (e.g., MATH with LLaDA-8B, MBPP-512 LLaDA) Polestar roughly matches or trails baselines in accuracy.
- Many hyperparameters (K, top-k, tau_upd, alpha, window sizes) are tuned on GSM8K and reported via ablations.
Experimental setup
Datasets: GSM8K MATH HumanEval MBPP ParallelBench
Benchmarks: GSM8K MATH HumanEval MBPP ParallelBench MathVista MathVerse
Metrics: accuracy tokens per forward (TPF) tokens per second (TPS) pass@1
Baselines: Baseline+Parallel Fast-dLLM Dynamic-dLLM Elastic-Cache d$^2$Cache EntropyCache AdaBlock-dLLM DAWN KLASS
Builds on: Fast-dLLM Elastic-Cache LLaDA KLASS DAWN
Closest papers by meaning
- dKV-Cache: The Cache for Diffusion Language Models (NeurIPS 2025 · similarity 0.92)
- Fast-dLLM++: Fr\'{e}chet Profile Decoding for Faster Diffusion LLM Inference (NeurIPS 2026 · similarity 0.91)
- EntropyCache: Decoded Token Entropy Guided KV Caching for Diffusion Language Models (NeurIPS 2026 · similarity 0.91)
- Orthrus: Memory-Efficient Parallel Token Generation via Dual-View Diffusion (NeurIPS 2026 · similarity 0.91)
- DAWN: Dependency-Aware Fast Inference for Diffusion LLMs (NeurIPS 2026 · similarity 0.90)
- Free Draft-and-Verification: Toward Lossless Parallel Decoding for Diffusion Large Language Models (NeurIPS 2026 · similarity 0.90)
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