arXiv subjects

Key Zhang

Publications and source records attributed to Key Zhang.

4 recordsLinked to original sources

arXiv2026

Hy-Nomas: Towards Free-form Interactive World Generation

Interactive world generation requires models to follow successive commands while preserving relevant history and action consequences. We present Hy-Nomas, a video world model with an 8B diffusion backbone that supports free-form text instructions and continuous camera control across multiple interaction turns. It generates variable-length segments conditioned on current inputs and cached history. Our central design aligns structured video captions with action-aware causal attention: descriptive context remains accessible across segments, while action instructions are restricted to their intended temporal windows. A vision-language Prompt Enhancer (PE) translates user requests and multimodal interaction histories into structured conditions for the next segment. A multi-stage curriculum progressively introduces causal generation, text interaction, camera control, and training on model-generated histories, followed by diffusion distillation. In human evaluation, Hy-Nomas shows superior performance over existing world models. We release model weights, code and benchmarks, together with a lightweight adaptation workflow, to support reproducible research on interactive world generation.

cs.CV↗

arXiv2026

HyScale: Scaling Long-Context Training for Learned Sparse Attention

We present HyScale, a long-context training system for learned sparse attention. Learned sparse attention is a promising architecture for million-token contexts, widely adopted in production since DeepSeek-V3.2. Selection, however, grows into the training bottleneck. For each query, it scores every previous token whereas sparse attention reads only $k$; worse, current systems materialize a full score table and repeat selection during recomputation. Our key insight is that the output of selection is not an activation, but rather a set of indices. Building on it, HyScale introduces HyTopK and selection replay. HyTopK finds each query's exact top-$k$ on the fly without a score table, while selection replay reuses forward-pass selection in recomputation. Together with holistic system optimizations tackling end-to-end training challenges, HyScale speeds up GLM-5.1 training on 1M-token sequences by 2.07$\times$ over Megatron-LM on 512 H20 GPUs. It also speeds up the CSA layers of DeepSeek-V4-Flash and the QSA layers of Qwen3.8-Flash-Next by 2.01$\times$ and 1.57$\times$ at 1M tokens on 32 H800 GPUs.

cs.AI↗

arXiv2026

HyDra: Demystifying and Taming Dynamic Context Parallelism at Production Scale

Long-context training runs on sequences whose lengths span orders of magnitude, and dynamic context parallelism (DCP) gives each sequence its own CP degree. Existing DCP systems either do not scale or perform poorly on mainstream models, leaving Megatron-Core (Mcore) DCP as the only option at production scale. Mcore DCP, however, sizes each degree to fit memory, which grows linearly with length while attention grows quadratically, so comparable token counts hide unequal computation. In our production 256K-context training job on more than 11K GPUs under Mcore DCP, per-rank microbatch times differ by up to 5x at similar token counts. The skew leads to a 46% pipeline bubble and a 13% data-parallel bubble. We present HyDra, a scalable load-driven DCP system. Its scheduler balances computation by pulling every rank toward one load target, and balance in turn makes that target solvable in closed form. It places sequences with lazy heaps rather than whole-pool scans. That balance asks for CP degrees larger than memory requires, so its CP engine nests an inner Ulysses group in a shallow outer ring, letting a higher degree lower computation and communication together. Evaluation at both scales shows consistent gains. On a 512-GPU testbed, HyDra raises throughput over Mcore DCP by 1.18x on average at 32K context and 2.48x at 256K. On a 2,048-GPU production job, it shrinks the pipeline bubble from 36% to 14%, cuts scheduling time by 2.3x, and raises throughput by 1.10-1.43x (avg. 1.25x) over Mcore DCP and 1.33-1.90x (avg. 1.59x) over static CP.

cs.DC↗

arXiv2026

ARGUS: Production-Scale Tracing and Performance Diagnosis for over 10,000-GPU Clusters

Large-scale LLM training requires always-on, fine-grained observability for effective performance diagnosis at scale. Coarse resource monitors alone cannot localize root causes, and fine-grained profilers incur prohibitive (5%-30%) overheads and massive trace volumes, making always-on deployment impractical in large production clusters. We propose ARGUS, a low-overhead, fine-grained, always-on tracing and real-time analysis system for training workloads in 10,000+ GPU-scale production clusters. ARGUS decomposes observation along the training call hierarchy into CPU call stacks, framework semantics, and GPU kernel execution, with always-on collection under a combined overhead of less than 2%. It builds a unified data pipeline and compresses raw kernel events by approximately 3,700x from 10 MB to 2.7 KB per rank per step. Its progressive diagnosis framework automatically isolates anomalous windows, straggler ranks, and degraded kernels through iteration-time, phase-level, and kernel-level analysis. Deployed for over six months on a 10,000+ GPU production cluster, ARGUS has supported continuous fail-slow detection and performance optimization. Our case studies further demonstrate its effectiveness across representative anomalies, including compute stragglers, link degradation, pipeline-bubble amplification, FlashAttention JIT stalls, and compute stragglers masked by communication symptoms.

cs.DC↗