DevLog

Turing’s Proof Design a turing machine (TM) that can compute all decidable languages Prove there exists a TM that can simulate a TM, i.e. the Universal Turing Machine (UTM) With the hypothesis, can the UTM compute all (not only decidable) languages? Using Cantor’s Diagonalization theorem, prove there exists uncomputable languages Sho... Read More

Introdution to Concolic Testing Concrete + Symbolic Testing Referenced the following source: DART: Directed Automated Random Testing, Presented by Markus Overview of Concolic Testing Execute with random (concrete) inputs (when you have no information go for the low computation approach) Collect path constraints (dynamic execution) ... Read More

Introduction Notes during problem solving. Problem Description Given an integer n, return an array ans of length n + 1 such that for each i (0 <= i <= n), ans[i] is the number of 1’s in the binary representation of i. Code void memoize_bit_count(int *arr, int arr_length); int *countBits(int n, int *returnSize); int *countBits(int n, int... Read More

Introduction Notes during problem solving. Problem Description You are given a 0-indexed string array words. Two strings are similar if they consist of the same characters. For example, "abca" and "cba" are similar since both consist of characters 'a', 'b', and 'c'. However, "abacba" and "bcfd" are not similar since they do not consist of ... Read More

Introduction Notes during problem solving. Problem Description Suppose you are given the following code: class FooBar { public void foo () { for (int i = 0; i < n; i++) { print("foo"); } } public void bar () { for (int i = 0; i < n; i++) { print("bar"); } } } The sa... Read More

List of what I should study during my summer vacation (2023 Jun ~ 2023 Aug). Subjects to study : 1) Fuzzing 2) Code Review 3) Seminar/Presentation 4) Operating Systems It was fun to compare with my goals last break. Subjects to study : 1) Operating Systems 2) Embedded Systems 3) Algorithms 4) Compilers (Maybe..?) Introduction 이번 방학은 계획이 달랐다... Read More

Introduction Notes during problem solving. Motivation After taking Operating Systems, I realized I needed more practice using C. Usually, I don’t like to do repetitive tasks, but desperate times call for desperate measures. Preperation Decided on the topics I will focus on solving first. Bit manipulation File I/O Pointers Problem Desc... Read More

Introduction This entry contains the notes of ch41 of Operating Systems. Getting Started The original file system structure was very simple and intuitive. It was composed of a superblock, inodes, and data blocks (you can picture it easily). Personally, it looks like a Pokemon health bar. However, it was slow.. and made no effort towards p... Read More

Introduction This entry contains the notes of ch40 of Operating Systems. Getting Started Things to remember before starting: What types of on-disk structures are utilized by the file system to orgranize its data and metadata? How does it map the calls made by a process, onto its structures? File Organization Data (User) Metadata... Read More

Introduction This entry contains the notes of ch07 & ch08 of Operating Systems. Prerequisites Mechanism The actual implementation to solve the desired goal. Policy A general algorithm to decide on what to execute. Assumptions Each job runs for the same amount of time. All jobs ar... Read More

Introduction This entry contains the notes of ch04 & ch06 of Operating Systems. Process What is a process? A running instance of a program The cool part is, as we will learn later, it is not always running. Computers without process, can run only one instance at a time. Co... Read More

Introduction This entry contains the notes of intro & ch02 of Operating Systems.<br> PDFs of my handwritten notes and lecture slides will be added. Abbreviations HW : hardware SW : Software CA : Computer Architecture What is Operating System? A program first loaded when a computer starts Then what is a comput... Read More

Introduction This entry contains the notes of ch15 of Operating Systems. Questions What if free had the size to be freed? Why does the header block have a magic number? The magic number in the header block is a special value that is used to validate the integrity of the header block. It is typically a fixed value that is stored ... Read More

An Empirical Study of Fault Localization Families and Their Combinations Goal: Resolve how techniques are correlated to each other. Measure the time cost of different fault localization methods. Points: Background Introduces 7 families of fault localization. Introduces the learning to rank model for combining differen... Read More

23-1 04/09/2023 How do humans know they don’t know? I remembered a part of a video clip I watched some time ago. It was about how computers (as expected..) “think”. The speaker gave an example, “Do you know the capital of (just an example) Morocco?”. Us humans “know” right away the absence of knowledge. I asked ChatGPT what it thought of this... Read More

Introduction This is my recording of what I’ve learned in the years 2015 ~ 2016 그림드림. Story In my elementary school, Central Christian Academy(CCA), there was an art club I really wanted to join. The club was called, “그림드림”, which ment DrawDream and also DrawGive. As I look back, I can confidently say this was one of the primary influences ... Read More

Introduction This is my notes on the order + details of lectures/labs as a TA. Code #if 1 #include "stdio.h" #endif #ifdef DEBUG #define DPRINT(func) func; #else #define DPRINT(func) ; #endif int main() { #if 1 #ifdef DEBUG printf("\nDEBUG - Hello World!\n"); #else printf("\nHello World!\n"); printf("Well Done! No... Read More

Introduction This is my collection of notes took during seminars I participated in. Sometimes as a presenter, discussion participant, or sometimes a normal listener:) November 25th, 2022 Graduate school seminar - Jooyong Yi Automated Bug Fixing Formal verification semi SapFix generate and validate (make and check) Search genetic... Read More

Metallaxis-FL: mutation-based fault localization Goal: A fault localization approach based on mutation analysis that uses mutants and links them with the faulty program places. Show it is more efficient than other fault localization approaches such as spectrum-based, block-based or branch-based test suites. Solve/Prove the most controver... Read More

Introduction While I was browsing on the Postech CS labrooms site, a certain topic caught my eye. Computing Systems. Feeling the enthusiasm I learned from my previous class in 22-2, Computer Architecture & Origanization (whew..), I instantly opened all three : https://sslab.postech.ac.kr https://hpc.postech.ac.kr/wordpress/ http://sy... Read More

Introduction My study notes of Computer Architecture & Organization. Took the class during 22-2. Note written during 22-Winter. What is Computer? The Von Neumann Architectue Just like coding, the basic architecture of a computer has an input -> process -> output. Typical computer organization Instruction Set Architecture ISA ... Read More

Introduction Gonna record what I’ve learned; as a learner (Studies + Humanities). ISEL, Intelligent Software Engineering Laboratory 22-2 Fall I actually joined the lab during my 4th semester. However, didn’t do much + started writing blogs during the winter vacation. Read More

22-2 ~ 23-1 Winter Vacation 02/20/2023 The Future of Humanity After lunch, JC took us(BJH, SC, SB) for a walk. We discovered a new path around HIS that lead to Papyrus Hall. We sat in the cozy room in the corner on 100,000+ won bean bags. The talk started off by comparing our current Handong experiences compared to his. There were a lot of diff... Read More

22-2 ~ 23-1 Winter Vacation 02/18/2023 These days, I’m feeling humbled. There are several reasons for this: My lab mates are more focused on researching then I am. I always had the thought that I was the only person passionate and willingly researching this area. Web applications are actually useful to learn. I... Read More

22-2 ~ 23-1 Winter Vacation 02/13/2023 It has been two weeks since my last entry.. Only 14 days till the start of 23-1.. Feeling real tired everyday, and I can see I don’t have much energy as before. The past two weeks I was mostly working on finishing my first paper and the presentation. I actually learned a lot during this time period and wish... Read More

22-2 ~ 23-1 Winter Vacation 01/25/2023 JC told us 3 values a professor is asked time and time again. Research Education Volunteer First, research is the most obvious one. As a researcher assigned to a university, a professor has the duty to constantly participating in researching. Second, Education. Professors are priveleged to be able to... Read More

22-2 ~ 23-1 Winter Vacation 01/16/2023 Had a weekly meeting, mainly discussed about how SC was doing. Also learned a lot while reviewing the big picture of APR and FL. The reason FL is needed is because the “buggy lines” are usually not the actual faulty line. Additionally, JC taught us about AST (Abstract Syntax Tree). This is needed becau... Read More

22-2 ~ 23-1 Winter Vacation 01/05/2023 Heard from one of my lab mates that keeping track of what you’ve learned and writing blogs is really important (whether you are aiming for employment of education). Felt more drive when I heard this. Thanks. Realized I really should keep up with studying research papers. Read More

22-2 ~ 23-1 Winter Vacation 01/02/2023 After a day in the lab, I went to the study room in Papyrus Hall to do my personal studies. My goal was to study till 23:00. When it was 22:48 I lost concentration and was about to go home (meaning the floor above), but remembered what JC told me. KOR : 랩실에 나오는 것을 기본 원칙으로 합니다. 혹시 조금이라도 늦거나 일찍 떠나야 한다면, 언... Read More

Introduction This is my notes on the order + details of lectures/labs as a TA. Order 1. Installation Process 2. Debugging I realized debugging should be the first to be taught (installation doesn’t count) because it is crucial in the later parts of the class and getting a habit of it is important to survive. This is a [link] (https://www.yout... Read More

Introduction While browsing youtube found a video of a guy talking about his college studies in Yale. And in one of his classes, he said they actually implemented a bash shell (not a script, amazing) . This reminded me how limited my current school was.. Couldn’t pass by this treasure:) Starting.. Luckily, during my Data Sturctures class (22-1)... Read More

Pondered on what I should study during my winter vacation (2022 Dec ~ 2023 Feb). Subjects to study : 1) Operating Systems 2) Embedded Systems 3) Algorithms 4) Compilers (Maybe..?) Others : 1) Introductory to Machine Learning; through Python (https://github.com/idebtor/KMOOC-ML) 2) Leetcode 3) Fault Localization Introduction I'm going to wri... Read More

정렬 알고리즘이란? 정렬 알고리즘은 목록의 요소들을 순서대로 넣는 알고리즘이다. -위키백과 정렬을 해야하는 이유? 데이터를 정렬해야 하는 이유는 탐색을 위해서이다. 사람은 수십에서 수백 개의 데이터를 다루는 데 그치지만 컴퓨터가 다뤄야 할 데이터는 보통이 백만 개 단위이며 데이터베이스 같은 경우 이론상 무한 개의 데이터를 다룰 수 있어야 한다. 데이터가 정렬되어 있다면 효율적으로 정보를 탐색할 수 있다. -나무위키 시작하기 전에.. 정렬의 종류가 다양한 이유 정렬 방법의 따라 시간복잡도가 다르다. 정렬 방법의 따라 공간복잡도가 다르다. Stable/unstabl... Read More