Sumit's Diary https://blog.reachsumit.com/ Welcome to Sumit Kumar's Personal Blog! Hugo -- gohugo.ioenhello@reachsumit.com (Sumit Kumar) hello@reachsumit.com (Sumit Kumar)Sun, 05 Oct 2025 00:00:00 +0000 Teaching Models to Decide When to Retrieve: Adaptive RAG, Part 4 https://blog.reachsumit.com/posts/2025/10/learning-to-retrieve/ Sun, 05 Oct 2025 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2025/10/learning-to-retrieve/ This final post of the Adaptive RAG series explores methods that treat adaptive retrieval as a learned skill and explicitly teach models when to retrieve. We examine three paradigms in increasing order of sophistication.]]> Probing LLMs' Knowledge Boundary: Adaptive RAG, Part 3 https://blog.reachsumit.com/posts/2025/09/probing-llms-knowledge-boundary/ Sat, 27 Sep 2025 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2025/09/probing-llms-knowledge-boundary/ This post introduces techniques that probe the LLM’s internal confidence and knowledge boundaries. We explore prompt-based confidence detection, consistency-based uncertainty estimation, and internal state analysis approaches to determine when retrieval is truly necessary.]]> Deciding When Not to Retrieve: Adaptive RAG, Part 2 https://blog.reachsumit.com/posts/2025/09/deciding-when-not-to-retrieve/ Sun, 21 Sep 2025 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2025/09/deciding-when-not-to-retrieve/ Building on part 1’s exploration of naive RAG’s limitations, this post introduces adaptive retrieval frameworks and pre-generation retrieval decision-making methods that determine if retrieval is truly necessary.]]> The Hidden Costs of Naive Retrieval: Adaptive RAG, Part 1 https://blog.reachsumit.com/posts/2025/09/problems-with-naive-rag/ Mon, 01 Sep 2025 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2025/09/problems-with-naive-rag/ Retrieval-Augmented Generation (RAG) isn’t a silver bullet. This post highlights the hidden costs associated with RAG and makes the case for a smarter, adaptive approach.]]> Embedding Collapse in Recommender Systems: Causes, Consequences, and Solutions https://blog.reachsumit.com/posts/2024/11/embedding-collapse-recsys/ Wed, 06 Nov 2024 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2024/11/embedding-collapse-recsys/ Learned embeddings often suffer from ’embedding collapse’, where they occupy only a small subspace of the available dimensions. This article explores the causes of embedding collapse, from two-tower models to GNN-based systems, and its impact on model scalability and recommendation quality. We discuss methods to detect collapse and examine recent solutions proposed by research teams at Visa, Facebook AI, and Tencent Ads to address this challenge.]]> Incorporating Ads into Large Language Models Outputs https://blog.reachsumit.com/posts/2024/08/ads-llm/ Sun, 11 Aug 2024 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2024/08/ads-llm/ This article provides an introduction to online advertising systems and explores research work that incorporates ads into the LLM responses to user queries of commercial nature.]]> The Evolution of Multi-task Learning Based Video Recommender Systems - Part 2 https://blog.reachsumit.com/posts/2024/06/multi-task-video-recsys-p2/ Sat, 22 Jun 2024 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2024/06/multi-task-video-recsys-p2/ This article continues the discussion on the evolution of multi-task learning-based large-scale recommender systems. We take a look at strategies from Kuaishou, Tencent, YouTube, Facebook, and Amazon Prime Video to disentangle input space and address systematic biases. The article ends with sharing several tips and learnings for professionals working in this domain.]]> The Evolution of Multi-task Learning Based Video Recommender Systems - Part 1 https://blog.reachsumit.com/posts/2024/06/multi-task-video-recsys-p1/ Sun, 16 Jun 2024 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2024/06/multi-task-video-recsys-p1/ This article introduces the multi-task learning paradigm adopted by various large-scale video recommender systems. It introduces a general setup for such an MTL-based recommender. It highlights several associated challenges and describes solutions adopted by various state-of-the-art recommenders in the industry.]]> An Introduction to Multi-Task Learning based Recommender Systems https://blog.reachsumit.com/posts/2024/01/multi-task-learning-recsys/ Fri, 26 Jan 2024 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2024/01/multi-task-learning-recsys/ This article provides an introduction and literature review for multi-task learning based recommender systems. We learn how to discover task relations, design MTL architectures and overcome some of the associated challenges.]]> A Guide to User Behavior Modeling https://blog.reachsumit.com/posts/2024/01/user-behavior-modeling-recsys/ Sun, 07 Jan 2024 00:00:00 +0000 Sumit Kumar https://blog.reachsumit.com/posts/2024/01/user-behavior-modeling-recsys/ Modeling users’ past historical interactions or behavior sequences is an essential task for domains like recommender systems, click-through rate prediction, targeted advertisement, and more. This article provides a comprehensive introduction to the user behavior modeling paradigm along with highlighting several relevant and recent research works.]]>