Long-context / context-window extension
H2O
H$_2$O: Heavy-Hitter Oracle for Efficient Generative Inference of Large Language Models
Superseded — cited as a baseline and beaten by newer methods
5 papers critique it · 3 beat it on benchmarks
What papers say
Verbatim critique sentences, each from a paper that cites H2O as a baseline.
Although these methods generally have low additional overhead, they often lead to noticeable performance degradation.
“While these methods differ in selecting tokens for KV cache retention, they generally apply a uniform budget size across layers, even though the optimal budget size may vary.”
“H2O maintains a fixed-size KV cache during decoding by dynamically evicting tokens.”
“both rely on manually designed patterns or rules, which limits their ability to capture highly input-dependent attention sparsity”
“H2O~zhang2024h2o reduces memory costs and achieves better accuracy than StreamingLLM, but its reliance on attention maps makes it incompatible with the efficient attention implementation FlashAttention~dao2023flashattention, leading to slow attention computation.”
Beaten on benchmarks
Head-to-head results where a newer method reports beating H2O. Values are copied from the source paper's tables — verify against the cited paper.
A2ATS beats H2O
86.3 vs 22.3
Accuracy · [MegaBeam-Mistral-7B-512K, Sparsity ~0.062]
A$^2$ATS: Retrieval-Based KV Cache Reduction via Windowed Rotary Position Embedding and Query-Aware Vector QuantizationCSAttention beats H2O
49.92 vs 37.45
Avg · [Mistral-7B-Instruct-v0.3]
CSAttention: Centroid-Scoring Attention for Accelerating LLM InferenceZigZagKV beats H2O
43.30 vs 40.00
What to use instead
Recent methods in the same sub-problem, not yet superseded in the knowledge base — arXiv benchmark leaders, not vetted production recommendations.