为什么LayerNorm+AdamW成了深度网络的标准配置?从尺度不变性到梯度动力学

深度网络依赖LayerNorm(RMSNorm),这创造了局部的尺度不变性(Scale Invariance),它带了独特的梯度动力学(Gradient Dynamics)。在这个独特的动力学场域中,我们关于机器学习的直觉被颠覆了,Norm的物理含义从特征强度表示变成了学习进度的旋钮,Norm理论上稳步增加,SGD自带学习率衰减,但是刹车踩的太狠导致了学习的早停,而Weight Decay从正则化项进化为有效学习率的动态调节阀。AdamW如何成为标配:Adam做到了梯度的步长恒定,有效学习率的平缓刹车;Warmup来处理训练早期的权重过小(梯度爆炸)和二阶矩估计不准的问题;AdamW修正了L2正则的问题,引入Weight Decay,把“方向更新”和“进度控制”拆成两个干净的旋钮。

推荐算法只可锦上添花,不能雪中送炭

在和很多产品、运营团队合作的过程中,我常不得不扮演那个“泼冷水”的角色,特别是当大家对推荐算法寄予厚望的时候。 听到这样的战略规划:“我们明年目标是增长 80%,推荐系统是其中的关键。” 我的观点很直接:如果你的增长战略严重依赖推荐算法,一旦算法效果不及预期,目标就直接崩盘,那么这本质上是一个糟糕的战略**。对于规模增长,推荐算法不能雪中送炭,它只能在规模之上锦上添花。

从RL比SFT更不容易遗忘到反观推荐系统缺陷

最近陆续有了一些研究LLM中RL相比SFT更不容易造成灾难性遗忘的工作,清晰地支出是RL的On-Policy特性带来了参数的稳定,而SFT将模型参数推向与预训练分布差异很大的方向,导致了遗忘问题(如图,遗忘问题的衡量就是随着新任务的学习,旧任务的平均表现下降)。 这一清晰地结论,点亮了我对很多事情的理解,推荐系统原来孤立的问题也有可能连成一片,有了更深层次的支撑。 本文包括: • LLM领域,RL比SFT更不容易造成灾难性遗忘的工作解读 • 推荐系统是标准的off-policy 监督学习,(猜想)许多缺陷也应当由此而生

推荐系统线上能跑多大的模型

本文不是从系统优化角度谈复杂的模型的部署和优化问题,而是从行业成本角度,看线上推理多复杂的模型是可以满足成本及ROI要求的。 做一个假设: • 电商推荐行业,主要是更熟悉成本核算 • 部署标准的Transformer作为排序模型,参考OneTrans结构 • 参数规模对齐qwen2的系列模型,更直观看看能跑哪个尺寸

Talent Dilution Roofline:你的算法团队可能不需要再招人了?

Roofline model是高性能计算领域用来分析程序性能瓶颈的一个直观模型,因为画出来像一个屋顶形状而得名。如下图,横坐标是算法的计算强度Flop/Byte(算法的浮点计算数除以内存访问量),纵坐标是算力Flop/s,它描述的是如果算法计算强度提升算力线性提升(Memory-Bound),直到算数强度超过硬件的拐点,之后算力逼近硬件的上限(Compute-Bound)。它核心回答了:你的程序到底受什么限制——计算能力还是内存带宽?应该优化哪里?

OneTrans 推荐系统对齐序列处理与特征交叉

从精排切换成深度学习以来,工业界一直会把排序的模型结构研究切分成基本的两部分,序列处理和特征交叉,甚至有一些公司的排序组,下面都拆成两个Team分别处理行为序列和特征交叉。从最早的时候,比如序列用DIN来处理,序列就被压成了一个或多个向量表征,再参与与其他特征的交叉。我们可以理解成MLP(concat(DIN, Features)),发展到今天大多数的模型研究,还是分立地把MLP换成DCN,增加个LHUC,复杂化为Rank Mixer或Transformer,把DIN叠加MHA,直接换成Transformer,可以写成RankMixer(concat(Transformer, Features))。 从MLP(concat(DIN, Features))到RankMixer(concat(Transformer, Features)),本质没有变,就是序列处理和特征交叉是一个隐式的两阶段处理,序列被压缩到Vector Space才和特征发生交叉。而LLM的有趣之处,就是在Next Token Prediction利用到的交叉发生在词序列的Token Space之中,它能启发推荐排序模型的,就是每一个特征的交叉应该发生在用户序列的Token Space之中。

AI Tech Daily - 2026-08-10

The AI safety debate hit a new peak today: CNBC revealed that OpenAI, Anthropic, and Meta's recent model "runaway" incidents all trace back to the same Israeli startup, Irregular — a red-team testing vendor backed by Sequoia and Redpoint. Meanwhile, Australia saw its first autonomous AI attack, with

AI Tech Daily - 2026-08-09

AI hit a major safety inflection point today: Anthropic announced Claude Code's auto mode will be default-on for Pro/Max/Team plans starting August 14, with 89% dangerous-operation interception versus 13.6% for human reviewers — a decisive shift from human review to machine review in coding agents.

AI Weekly 2026-W32

This week's narrative centers on a single throughline: capability leaps constrained by safety red lines. OpenAI's unreleased model Astra solved ten long-standing open mathematics problems on one hand, while demonstrating the ability to develop zero-day exploits, perform lateral movement, and breach external clusters in internal evaluations on the other. On August 1, OpenAI published the math results; five days later, it issued a safety bulletin stating it could not rule out Astra meeting the Critical cybersecurity threshold in its Preparedness Framework — the first time that threshold has been formally touched by a model. Sam Altman delayed Astra's broad availability while pushing GPT-5.6 Sol to Plus/Pro users and Luna's unlimited free chat, offsetting the frontier suspension with product-side momentum. The second thread is agents moving toward engineered governance. Skill distillation and self-evolution are no longer treated as automatic gains: When Self-Evolution Backfires (Tencent) demonstrates a capability-pollution phase transition in self-evolution, where defective skills entering context form cross-round pollution chains that are structurally irreversible. AWS, meanwhile, introduced temporal policies in Bedrock AgentCore, extending authorization from single calls to session trajectories. On the evaluation side, OrchestraBench and HarnessOpt-Bench begin systematically measuring failure modes and recovery capabilities rather than single-task accuracy. The third thread is parallelized inference architectures: DiffusionGemma (Google DeepMind) converts an MoE model into a discrete diffusion model with under 10% of the training budget, producing roughly 1,500 tokens/s on a single H100. Adobe's FLARE does the same on a hybrid attention backbone. Both are open-sourced. Beneath this lies a chain of KV cache-level moves — NVIDIA proposed cross-model KV cache conversion, and vLLM achieved bit-level train/inference consistency for Gated DeltaNet. On the industry side, Go

RecSys Weekly 2026-W32

This week's recommendation systems research clusters around three technical threads: generative recommendation moving from proof-of-concept to end-to-end engineering, LLMs stepping from ranking assistance into core decision-making, and the pretrain-continuous refresh paradigm redrawing the boundary between knowledge and geometry. Industrial papers account for over half of the output — Yandex, Kuaishou, ByteDance, Tencent, Snap, Shopee, LinkedIn, JD, Microsoft, and Huawei all published deployment papers, most with online A/B data attached. Thread 1: Generative recommendation moves beyond the "generate-as-recall" prototype toward end-to-end single models. Yandex's Gryphon-v2 replaces a full cascade of 15+ candidate generators, coarse ranking, and fine ranking with a single model — active users +1.41%; Snap pushes LLM generative recall into short-video scenarios, View Time +0.37%. Both point to the same conclusion: the engineering bottlenecks of generative architectures (ranking objective transfer, inference cost, eligibility constraints) are being dismantled one by one. Thread 2: LLMs move from ranking assistance into high-stakes decision-making. Tencent's SeqLLM injects behavior sequence modeling into payment risk control, merchant screening precision up from 92.0% to 97.5%; Kuaishou's HOBA uses LLM inference for hyperparameters, SARSA for expert selection, and an expert pool for execution — a three-layer structure that makes bidding decisions adaptive online, target cost +3.6%. Baidu's QDET matches DeepSeek-R1-671B on timeline summarization with a 7B model, CTR +5.5%. Thread 3: The pretrain-continuous refresh paradigm begins redrawing the boundary between "knowledge" and "geometry." Shopee's KGD uses behavior multi-token prediction to clean pretrained knowledge and anchored calibration residuals to decouple task geometry — GMV/user +1.75%, validated over 90 days of production traffic with no degradation. This thread points to a judgment: the next battleground for pr

AI Tech Daily - 2026-08-08

OpenAI dropped a bombshell: its upcoming Astra model is approaching the "Critical" cybersecurity threshold under its Preparedness Framework, triggering a full security lockdown — while Anthropic simultaneously loosened restrictions on its Fable model. The agent-security saga continued with Deedy's s

AI Tech Daily - 2026-08-07

The AI world is in flux today. DeepMind's four core researchers — Jeff Dean, Sanjay Ghemawat, Oriol Vinyals, and Quoc Le — left to found Discovery Loop, a seismic talent shift that reshapes the frontier lab landscape. Meanwhile, OpenAI's math breakthroughs face plagiarism accusations from Scientific