Category: Notes

• Revisit Frontend 101: Cookie

  Despite developed front end programs with the witness of 30k+ lines of code and several projects, big or small, mastering React framework and its pals (like Zustand, vite, etc.) when I was asked about some basic concepts, I felt so dumbed that lead me here to take some notes.

  Cookie, what a corny term. As I can remember, I have been working with front end techs without Cookies for a long time, which is almost cleared from my memory. Technically, it is a storage with a very little capacity (4 kB) can be manipulated from both front end and back end, except for those with HTTP only attribute.

  I was asked about the fields of Cookie and I fail to put forth an answer. Here’s the answer:

  • Core Fields: Name=Vlue, Expires, Max-Age, Domain, Path, Secure & HttpOnly,
  • Expanded Fields: SameSite, Partioned, Priority, SameParty.

  I will emphasize core fields in details as it matters the security and being of a cookie.

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  September 7, 2025

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• Obstacles on and decisions behind a journey to an RAG system

  Recently, I was assigned to build an RAG system to mitigate LLM’s hallucination on proprietary documents. I can take advantage of the given pre-trained BERT/Roberta models and an API towards a gte model as an encoding service as project resources. Therefore, I don’t need to build the system from scratch. Here’s something I learned from this project from obstacles and my decisions.

  RAG, a bird’s-eye view.

  Let’s quickly review RAG for those who did not get acquainted with it. If you already know about it, skip this section.

  RAG, Retrieval Augmented Generation, is a practical approach to alleviate the hallucination problem of LLM. Hallucination means a status when LLM cannot respond to users’ input correctly, even concoct misinformation in a severe tone. This usually happens when LLM meet a problem which does not exist in its training dataset. RAG fixes this problem by furnishing the LLM with relevant information as prompts embedded into the user’s input prompts. This was first formulated in (Jiang et al., 2023) by a team whose members are from Facebook, UCL, and NYU. The name of RAG indicates that the system comprises three components (or processes): Retrieval, Augmentation, and Generation. Making each part happens can produce an LLM, which tells jargon.

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  April 24, 2024

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• On Some NumPy Functions

  Recently, I have been working on a Recommender System model, and I frequently use NumPy to preprocess data before feeding them into the PyTorch model. I have discovered some problems in NumPy functions, so I am sharing them as my experience and a part of my coding notes.

  np.datetime64 This is a data type addressing date and time data in a NumPy matrix. However, it looks like this function is quite costly. When indexing on a matrix with np.datetime64 column(s), the processing will become very slow. Here’s my advice: avoid using it, and try to replace it with some other measures. For example, if you want to do some simple arithmetic on days, you’d better operate integer plus or minus n*24*60*60 on timestamp; do not convert it to a np.datetime64 type.

  np.datetime64 is stored as int64 in memory. If you try to store it as int32, it will overflow.

  When you concatenate an int32 matrix with an int64 matrix, int32 will convert to float64 automatically, not int64, due to the difference in precision and length.

  np.isin This is a function try to detect whether an element in a NumPy container exists in another NumPy container. It is useful when we try to do intersection operations between a matrix and a vector, specifically if we have a matrix and we want to filter the matrix by doing an intersection on a column of this matrix with another specified vector. In this scenario, other intersection functions are not applicable, such as np.in1d or np.intersect1d. However, this is also a costly function. Therefore, the only way I can do now to accelerate this function is to leverage multiple processes.

  These are my observations. If you find any error or disagree, it is welcome to discuss it below.

  November 6, 2023

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