Notes on Introduction to Information Retrieval, Chap. 1. (Boolean Retrieval)

Unknown — Fri, 12 Jun 2026 00:00:00 +0000

1.0 Background Information</h1>

IR: Finding materials that satisfy an information need from unstructured data

Information retrieval (IR) is finding material (usually documents) of an unstructured nature (usually text) that satisfies an information need from within large collections (usually stored on computers). </blockquote>

Unstructured data

No clear structure => difficult for computer Clustering</li>
Task of producing a suitable grouping of documents based on their contents Classifying</li>
Task of deciding which class(es) a document within a collection belongs to Scales of IR</li>
Web Search

Billions of documents stored over millions of computers</li> </ul> </li>
Enterprise

Internal documents within a corporation's collection, more domain-specific</li> </ul> </li>
Personal Information Retrieval

Documents on a personal computer, handled in a lightweight manner</li> </ul> </li> </ul>
1.1 Boolean Retrieval Problem Simplified</h1>
Scenario #1</h2>
Consider a collection of plays (Shakespeare's Collected Works)

Target: Determine which plays contain the words "Brutus" AND "Caesar" AND NOT "Calpurnia"</code>.</li>
Simple Method: Linear scan through collection (or grepping), positive result if target conditions of query are satisfied Note for each play whether it has "Brutus" and "Caesar", exclude if it contains "Calpurnia"</li> </ul> </li> Limits of simple method Can't process large collections efficiently</li> Inflexible matching operations (e.g. if we want a query with definable relationships between words instead of just logical)</li> Doesn't pick the best answer (not ranked retrieval)</li> </ul> </li> Overcoming linear scans: Consider indexing the documents in advance Method For each document, record whether it contains each word out of all the words Shakespeare has used (approximately 32,000 words)</li> Results in binary term-document incidence matrix (Fig. 1.1). The terms are indexed units. "term-document" as in a term-to-document relationship within the matrix. "binary" as in values are only true or false </blockquote> </li> </ul> </li> Refer to Fig. 1.1</li> We can have either a column vector (for each document, show the occurring terms), OR a row vector (for each term, show the documents it occurs in)</li> To solve initial proposed target, we take row vectors for Brutus</code>, Caesar</code>, and Calpurnia</code>, and perform a bitwise AND operation</li> Result: 110100 AND 110111 AND 101111 = 100100</code>. Hence, Antony and Cleopatra</code> and Hamlet</code> are the answers. Note that we invert the last column vector (Calpurnia) in order to satisfy the NOT operator in our query </blockquote> </li> </ul> </li> </ul> </li> </ul> </li> </ul> The Boolean retrieval model allows us to pose a query in the form of a Boolean expression of terms. Each document is viewed as a set of words. Scenario #2</h2> Consider a larger-scale scenario with a collection of N = 1 million documents that are roughly 1000 words long each. Generally, there might be about M = 500,000 distinct terms throughout the collection. Goal: Address the ad hoc retrieval task where we aim to provide documents relevant (perceived as containing information of value with respect to their need) to some user information need (topic which user wants to know more about), communicated through a one-off, user query (what user conveys to computer to try to communicate their need)</li> Assessing effectiveness (quality of search results) Precision Fraction of returned results that are relevant to the information need</li> </ul> </li> Recall Fraction of relevant documents in the collection that were actually returned</li> </ul> </li> </ul> </li> Limit: term-document matrix is not a viable solution, too large. However, note that there are few non-zero entries because each document is only a 1000 words long. Matrix would have 500,000 rows (distinct terms) * 1,000,000 columns (documents) = 500 billion cells. Since each document has a general length of being a 1000 words long, assuming all terms in each document are distinct, at most 1,000,000 documents * 1000 distinct terms per document = 1 billion. So there is a maximum of 1 billion 1's out of 500 billions cells. 99.8% of the cells are zero. </blockquote> </li> </ul> </li> </ul> </li> Overcome limit: Record only the 1 positions. Inverted index Concept Keep a dictionary (refers to the data structure used) of terms.</li> For each term, there will be a list that records which documents the term occurs in</li> , Each item in the list is called a posting</li> The list is known as a postings list</li> All postings lists are collectively known as the postings</li> </ul> </li> </ul> </li> </ul> </li> </ul> 1.2 Building an inverted index</h1> Steps Collect documents to be indexed</li> Tokenize text so each document is a list of tokens</li> Preprocessing to normalise tokens</li> Index documents that each term occurs in by creating an inverted index</li> </ol> Consider a scenario in which steps 1-3 are done. Now we perform step 4. Indexing Method Assign each document a unique docID</li> Input to indexing method will be pairs of term and docID (Fig. 1.4)</li> Sort the list with terms alphabetically</li> Merge terms that repeat in the same document</li> Group instances of the same term</li> Split them into dictionary and postings</li> Sort postings by docID</li> </ul> Singly linked lists or variable length arrays are good structures for postings lists. 1.3 Processing Boolean queries</h1> Target: Combine inverted index and Boolean retrieval model Consider the statement: Brutus AND Calpurnia</code> Locate Brutus</code> in Dictionary</li> Get its postings</li> Locate Calpurnia</code> in Dictionary</li> Get its postings</li> Intersect the postings lists Simple intersection algorithm INTERSECT(p1, p2) answer <- {} while p1 != NIL and p2 != NIL do if docID(p1) = docID(p2) then ADD(answer, docID(p1)) p1 <- next(p1) p2 <- next(p2) else if docID(p1) < docID(p2) then p1 <- next(p1) else p2 <- next(p2) return answer // x+y intersections are done where x = size(doc(p1)), y = size(doc(p2))</code></pre></li> </ul> </li> </ul> </li> </ul> Through this form of indexing, complexity is improved by a constant (although still linear), but it's a huge difference in practice. Query optimisation is the process of selecting how to organise the work of answering a query so that the system does minimal work. Consider a query that is an AND</code> of t</code> terms, optimise intersection by: Intersecting the two smallest postings lists</li> All intermediate results will be at most the size of the smallest postings list "intermediate" in the sense that they are temporary results that come after the starting result, working towards the final result </blockquote> </li> Code: </blockquote> INTERSECT({t1, ..., tn}) terms <- SORTBYINCREASINGFREQUENCY({t1, ..., tn}) result <- postings(first(terms)) terms <- rest(terms) // rest of the terms while terms != NIL and result != NIL do result <- INTERSECT(result, postings(first(terms))) terms <- rest(terms) return result</code></pre></li> </ul> </li> If you have a hard time accepting it, try going through this scenario. Let N1=2, N2=100, N3=50</code> where Nn</code> represents the size of the postings list. Now see what happens when you compare N2</code> and N3</code> first instead of N1</code> and N3</code>. </blockquote> </li> </ul> </li> </ul> Many ways to modify and optimise intersection depending on the situation. Even the standard intersection algorithm is essential in certain cases. 1.4 Extended B.R.M. vs Ranked Retrieval</h1> Some systems have extended the Boolean retrieval model by incorporating operators such as term proximity operators (helps specify that two terms must occur within a certain distance of each other). Problems with B.R.M. Document either matches query or does not</li> AND operators lead to high precision but low recall</li> OR gives low precision but high recall</li> Lack of middle ground</li> </ul> Ranked retrieval models (like vector space models) possess certain advantages, and allows for free text queries. Figures</h1> Fig. 1.1</th> Antony and Cleopatra</th> Julius Caesar</th> The Tempest</th> Hamlet</th> Othello</th> Macbeth</th></tr></thead> Antony</td> 1</td> 1</td> 0</td> 0</td> 0</td> 1</td></tr> Brutus</td> 1</td> 1</td> 0</td> 1</td> 0</td> 0</td></tr> Caesar</td> 1</td> 1</td> 0</td> 1</td> 1</td> 1</td></tr> Calpurnia</td> 0</td> 1</td> 0</td> 0</td> 0</td> 0</td></tr> Fig. 1.3</td> </td> </td> </td> </td> </td> </td></tr> </tbody></table> Brutus -> {1, 2, 4, 11, 31, 45, 173, 174}</code></li> Caesar -> {1, 2, 4, 5, 6, 16, 57, 132, ...}</code></li> Calpurnia -> {2, 31, 54, 101}</code></li> LHS: Dictionary</li> RHS: Postings</li> </ul> Fig. 1.4 term</th> docID</th></tr></thead> I</td> 1</td></tr> did</td> 1</td></tr> enact</td> 1</td></tr> caesar</td> 1</td></tr> caesar</td> 1</td></tr> enact</td> 2</td></tr> Sorts into</td> </td></tr> </tbody></table> term</th> docID</th></tr></thead> caesar</td> 1</td></tr> caesar</td> 1</td></tr> did</td> 1</td></tr> enact</td> 1</td></tr> enact</td> 2</td></tr> I</td> 1</td></tr> Merges and splits into a structure like in Fig. 1.3</td> </td></tr> </tbody></table> C Language Cheatsheet Unknown — Thu, 11 Jun 2026 00:00:00 +0000 This is a C language cheatsheet I made, tailored to the ENGG1110 Problem Solving by Programming class. I believe this class is a foundational course for all engineering students. I think it may be of help to others who enter the course with some prior knowledge of programming, and just need to pick up some C. Personally, it was all that was necessary for a good grade (A) in the course, but results may vary of course. It's worth noting that the notes are not very organised nor does it follow the curriculum structure, it's just bits and pieces of information I thought worth recording. However, all content does pertain to what was taught. Notes</h1> int x = 5.99</code> => x = 5</code></li> Remember that characters are actually 1-byte integer values that represent an ASCII character. So, char a = "A" actually has an int value of 65 according to the ASCII table.</li> </ul> </li> Type-casting a float to an integer performs a floor operation on the value. e.g. (int) 0.99 + 5</code> => 5</code></li> </ul> </li> Any variables declared within the initialisation of the for loop and its body is scoped to the loop. However, the initialisation may make use of a variable declared in the outer scope. int i=0; for (i=1; i<3; i++) { printf("%d ", i); } printf("%d", i); // result is: "1 2 3"</code></pre></li> </ul> </li> </ul> </li> The escape character \</code> is not regarded as its own individual character. Only the escape sequence in its entirety is regarded as a single character. length("\\a"); // results in a string of length 2 (because the printed string is "\a")</code></pre></li> They also occupy the same index within a character array.</li> </ul> </li> By default, C uses pass by value for all arguments (except arrays, which practically pass by reference) When it comes to arrays Instead of passing a copy of the array, a pointer to the first element of the array is passed (array decay -> the array variable decays into a pointer, so information about the array is lost like size)</li> void myFunction(int *arr) { // Equivalent to passing int arr[] }</code></pre></li> When you modify the passed array (either through pointer arithmetic or indexing), it changes the original array. So in effect, it's pass by reference.</li> The name of an array itself can be treated as a pointer to its first element (arr = &arr[0]</code>). However, there are still some differences. It is not entirely equivalent. Generally, in an expression, the array name decays to a pointer to the first element of the array, excluding its use in sizeof</code>(returns size of entire array in bytes) and unary &</code> (int (*ptr_to_array)[5]=&array_size_5</code> points to the entire array.</li> </ul> </li> </ul> </li> When the size of an array is not stated, it is initialised to fit the initial declaration.</li> You have misunderstood the order of precedence and associativity in C. Precedence tells us which operator comes first, and associativity tells us the direction in which operators of the same level are evaluated.</li> E.g. double x = 5 / 2 * 4.0</code> /</code> and *</code> are on the same order of precedence, hence the expression is evaluated from left to right.</li> </ul> </li> Be wary of integer divisions and floating-point divisions. double x = 5.0 / 2 * 4.0</code> results in 10.0</code> because 5.0/2</code> is a floating-point division which results in 2.5</code>.</li> double x = 5 / 2 * 4.0</code> results in 8.0</code> because 5/2</code> is integer division, which results in 2</code>.</li> </ul> </li> In C, 0</code> is regarded as false, and all other non-zero values are regarded as true (including doubles & integers).</li> Format Specifiers in C %d</code> or %i</code> for signed integers</li> %f</code> for floating-point values, defaults to printing to the 6-th decimal place.</li> %.xf</code> where x</code> is an integer results in printing a floating-point value to the x-th decimal place. x=0</code> results in an integer result.</li> %c</code> for a single character</li> %s</code> for a string/(array of characters).</li> %u</code> for unsigned integers</li> %%</code> to print a literal percentage sign</li> Use of whitespace %c</code> skips leading whitespace and reads the first non-whitespace character</li> %c </code> reads any character, skips trailing whitespace until non-whitespace</li> scanf</code> reads the input buffer character after character, sequentially, including \n</code> when the user presses enter</li> </ul> </li> </ul> </li> Escape Sequences in C \n</code> next line</li> \t</code> horizontal tab</li> \\</code> backslash character</li> There are many more, not just the ones stated here. So be wary of that.</li> </ul> </li> Strings The ASCII value of 0</code> is the NUL</code> character, which is the string terminator \0</code>. It is not included when we call strlen</code>. However, in the actual size of the character array, it has to be taken into account.</li> For example, if we want a string of at most 100 characters, we need to declare an array of size 101 to include the string terminator</li> </ul> </li> Reading a string char str[100]; scanf("%s", str); // notice that prefix & is not needed for strings because of array decay</code></pre></li> Functions strlen(str1) -> length of string</code></li> strcpy(dst, src)</code></li> strcat(dst, src)</code> (appends src</code> to end of dst</code>)</li> strcmp(str1, str2) -> 0 : identical; <0 : first non-matching character in str1 less than corresponding character in str2; >0 : vice versa</code></li> </ul> </li> </ul> </li> </ul> </li> Note that type-casting takes precedence over calculations. E.g.</li> double a = -3.6; printf("%d\n", (int) (a + 0.5)); printf("%f\n", (int) a + 0.5); ```</code></pre></li> The above code results in '-3' and '-2.500000'.</li> '-3' : it first calculates the result in a+0.5, and then type-casts the result to an int.</li> '-2.500000' : following precedence, it first type-casts a to an int (-3</code>) => -3 + 0.5 = -2.5</li> </ul> </li> Size of data types Integer - 4 bytes</li> Float - 4 bytes</li> Double - 8 bytes</li> Character - 1 byte</li> </ul> </li> Extracting each digit from an integer int a; int n = 3; scanf("%d", &a); for (int i=0; i<n; i++) { printf("%d\n", a % 10); a /= 10; if (a <= 0) { i = n; } }</code></pre></li> </ul> </li> Postfix and Prefix Increment/Decrement ++variable</code> Variable is incremented before its value is used in the expression.</li> Result of the expression is the incremented value of the variable.</li> </ul> </li> variable++</code> The variable's current value is used in the expression first.</li> The variable is then incremented after its value has been used.</li> The result of the expression is the original value of the variable before the increment.</li> </ul> </li> </ul> </li> An assignment operation evaluates to the newly assigned value x=5 => 5</li> z = 0 => 0</li> x+=5 => x=x+5 => x+5</li> </ul> </li> Function Prototype or Forward Declaration in C This is a statement that describes a function's details (name, parameters, return type) before its definition.</li> It's used when you want to reference or call a function before its definition in your source code.</li> #include <stdio.h> int sum(int x, int y); int main(void) { int Sum = sum(x, y); return 0; } int sum(int x, int y) { return x+y; }</code></pre></li> Because it's troublesome to maintain, it should only be used when necessary.</li> </ul> </li> ASCII Table Non-Printable Characters (definitions) NUL : String-terminator/Null-character/'\0'</li> </ol> </li> SOH :</li> </ol> </li> </ul> </li> Remember that array declarations are as such char name[5]</code></li> </ul> </li> char getchar(void)</code> This function has no parameters. It reads the first character entered into the input stream and returns it.</li> char x = getchar()</code></li> </ul> </li> In C, local variables take precedence over global variables when they share the same name within the scope of a function or block. This is known as variable shadowing.</li> File IO Reading a fileFILE *fptr; fptr = fopen("file.txt", "r"); if (fptr == NULL) { // file failed to open return 0; exit(1); // only when stdlib.h included; alternative } // APPROACH 1 - Controlled Reading char character; for (int i=0; i<10; i++) { fscanf(fptr, "%c ", &character); /* - reads like scanf would but from a file - adding that whitespace "%c " allows us to skip newlines and whitespaces found in the stream */ printf("%c ", character); } // APPROACH 2 - Line after line to the end while (fscanf(fptr, "%c ", &character) != EOF) { printf("%c ", character) } fclose(fptr); ```</code></pre></li> fscanf</code> returns the number of items successfully read. If it reaches the end of file or an input error occurs, a constant EOF</code> is returned. Hence it is our terminating condition in the while loop 0</code> can also be returned, which means the input read didn't conform to the type specified by the format specifier.</li> </ul> </li> Writing to a file FILE *fptr; fptr = fopen("data.txt", "w"); if (fptr == NULL) return 0; // OR exit(1) fprintf(fptr, "Hello!\n"); for (int i=0; i<10; i++) { fprintf(fptr, "%d ", i); } fprintf(fptr, "\n"); fclose(fptr); /* Content: Hello! 0 1 2 3 4 5 6 7 8 9 */</code></pre></li> </ul> </li> </ul> </li> fgets(char_array_to_store_into, max_characters, input_stream)</code> Reads at most max_characters-1</code> or until a newline character appears. The newline is included in the character array. It also automatically appends a null terminator.</li> </ul> </li> scanf</code> for string reading Only includes up to the first whitespace character, unlike fgets</code></li> </ul> </li> In C, you cannot directly assign one array to equal to another. For character arrays, use strcpy</code> if necessary. Or memcpy(dest_arr, src_arr, sizeof(src_arr))</code></li> Structures struct student { char id[11]; char name[40]; double gpa; // int day, month, year; (acceptable) }; struct student peter; peter.id = "1155123456"; peter.name = "Peter Pennyworth"; peter.gpa = -1.5; struct student amanda = {"1155325932", "Amanda the Baboon", 3.2}; struct student amanda_cpy; amanda_cpy = amanda; // copies info over typedef struct { double lat, lng; } GeoLoc; struct place { char name[200]; GeoLoc centre; }; struct place HK = {"Hong Kong", {22.28, 114.17}}; // this is also valid</code></pre></li> When referencing a user-defined struct data type, we need to include this : struct defined_name</code>, it cannot just be the name we defined, unless we create a typedef</code>.</li> typedef struct type_name alias_name</code> Defines an alias for any existing type</li> Structs are also pass by value into a function unless a pointer is used.</li> </ul> </li> </ul> </li> Macro #define MAX_COUNT 30</code></li> Defines a referenceable constant</li> </ul> </li> Pointers// pointers are a distinct data type in C, declared using *ptr_name int n = 3; int *p = &n; // &variable -> address of variable (referencing) // to change address of existing pointer is p = &newaddress printf("%d\n", *p); // *ptr -> dereferencing pointer -> value at pointed address // p = &n (stores in p the memory address of n); *p = n (accesses value in memory address stored in p); printf("%d, %d\n", p, &n); // OUTPUT : address of n twice *p = 0; // manipulates n printf("%d", n); // n = 0 int **ptr = &p; // pointer to a pointer</code></pre></li> Dynamic Memory Allocation malloc(size_in_bytes)</code> This function allocates a single block of contiguous memory at runtime according to the size specified. Note that it is in bytes.</li> Hence, we usually use sizeof(data_type) * no_of_elements</code> for its parameter. sizeof(data_type)</code> returns the size of the data type we specify in bytes. E.g. m (int) -> 2 bytes</code>, sizeof(char) -> 1 byte</code></li> It can return NULL</code> if allocations fails. So we ensure we check for that condition.</li> The function returns a pointer to the allocated memory, which is inherently void, so we need to perform type casting.</li> The allocated memory is not initialised, hence filled with garbage values. So it shouldn't be read without writing to it.</li> </ul> </li> #include <stdio.h> #include <stdlib.h> int main(void) { int numOfGrades; printf("Enter the number of grades: "); scanf("%d", &numOfGrades); char *grades = malloc(sizeof(char) * numOfGrades); // -> returns a pointer to the base address of the allocated memory, equivalent to returning a pointer to the start of the array that we want if (grades == NULL) { // ESSENTIAL, avoids segmentation faults return 1; } for (int i=0; i<numOfGrades; i++) { printf("Grade #%d: ", i+1); scanf(" %c", &grades[i]); // " %c"; whitespace is needed to avoid capturing the newline character that enters the input stream when we enter numOfGrades and type "ENTER". } for (int i=0; i<numOfGrades; i++) { printf("Grade #%d: %c\n", i+1, grades[i]); // we do not need to do *grades[i] here because dereferencing is implied } free(grades); // essential to free the memory locations (since we're just "borrowing it") to avoid memory leaks grades = NULL; // avoids a dangling pointer that would point to deallocated memory return 0; }</code></pre></li> </ul> </li> Static Variables Static variables are initialised only once, and retain their value between function calls.</li> Example 1 int fun() { static int count = 0; count++; return count; } int main() { printf("%d ", fun()); printf("%d ", fun()); return 0; } // OUTPUT: 1 2</code></pre></li> </ul> </li> It's not destroyed upon function return</li> </ul> </li> int i, j, x = 5</code> doesn't initialise all three variables to 5</code> like Python would. It declares i, j</code> and only initialises x</code> to 5. The others would be garbage values.</li> Width specifier In printf</code> It specifies the minimum number of characters the output should occupy. If the output given is shorter than the minimum width, the output will be padded by whitespace.</li> E.g. printf("%5d\n", 42) // OUTPUT: " 42"</code></li> </ul> </li> </ul> </li> In scanf</code> It specifies the maximum number of characters to be read</li> scanf("%5d", &n); // reads at most 5 digits</code></li> </ul> </li> </ul> </li> </ul> Website Update Unknown — Thu, 11 Jun 2026 00:00:00 +0000 This is just a quick update to get me back into the loop of blogging. I've revamped the website by switching from Wordpress to a little SSG (Static Site Generator) called Zola. Zola is now the backbone of my blog, and I am enjoying it so far. It removes certain barriers to a more free form of blogging, which is what I intend to do. It does so in a couple of obvious ways. First of all, I can do all my writing entirely offline because I can run the site locally before I manually deploy it. </li> Secondly, I can use plain simple markdown (or technically "CommonMark"), which I feel is faster than having to slowly format things in a word processor-esque GUI (I have also had plenty of Markdown practice thanks to my heavy use of Obsidian). </li> Thirdly, Zola is extremely fast. It was built in Rust, which is a strong competitor to C++. For example, after saving this file, it detected changes and redeployed them within the short duration of 211ms. </li> </ul> The main hassles with a CLI-based SSG is embedding pictures into my pages. It's a little more trouble because I can't just copy and paste a picture or resize it freely. I guess it deters me from flooding my posts with images, and keeps things as minimalist as possible while conserving preicious storage. Anyways, that's the end of this update. I hope to be posting more as I dive into AI/ML. The Quarrasi Lock Online: My first web-hosted application Unknown — Thu, 05 Sep 2024 00:00:00 +0000 As a quick getaway from academics after a whirlwind of exams and a refresher into programming, I made my first leap into browser game development. Now this is something I’ve worked on indirectly (in the form of offered help), but hardly dirtied my hands with. This project is simple and was in fact completed over a matter of hours, so what deems this “blog-worthy”? Well, since it’s a simple vanilla JavaScript game, it’s much easier for me to host it on this website as compared to my other projects, which are either too large in scale or lacking in compability. The fact that I’ve always wanted to host an application on my website is also a contributing factor. This puzzle is now something anyone can try from anywhere, without having to go through all the hassle of downloading the projects files in order to run it. That’s the beauty of the web. It’s also, to my knowledge, a one-of-a-kind application as I haven’t seen any other visual interfaces for this puzzle. Delta Time - The Road to Frame Rate Independence Unknown — Sun, 22 Oct 2023 00:00:00 +0000 The word “delta” can be defined as the difference between two things or values. This was a word I first came across through physics, with delta(represented by a triangle) describing the change in a certain value. So from there, we can draw the conclusion that delta time is the change in time. In game development terms, it’d specifically represent the time that passes between each frame drawn. Why do we need delta time? Delta time allows us to achieve what is known as “frame rate independence”. That means, regardless of how low or high your framerate is, the rate at which things occur or are updated(for example, the change in object positions according to velocity, the rate at which an object’s velocity increases) remains consistent throughout the game. For example, if we were to be updating a flying object’s position by a velocity of 20 pixels per second toward the north, having frame rate independence would help us ensure that regardless of whether we’re getting 30 frames per second on one computer or 60 frames per second on another, the position of that flying object on both computers would remain the same after each second. How do we implement it? Let’s continue building off of the example that we used above. Our goal is to update an object’s position so that they move 20 pixels toward the north every second. First things first, let’s calculate delta time. This can be done by calculating the reciprocal of the player's frame rate, giving us the time between each frame (let’s say that value is 1/60 because the player’s frame rate is 60fps, do take note that in the real code implementation you won’t know what the frame rate is, you need to take the frame rate with whatever function your library or your engine supports). Now, we multiply the velocity of 20 pixels per second to the north by delta time, which reduces the velocity so that after 60 frames, i.e a full second, the object’s position would have moved by approximately 20 pixels towards the north. In this case, our object’s position would be updated by 0.3333 pixels towards the north every frame. So by the end of 60 frames, our object would have moved by 0.3333 * 60 = 19.998 pixels toward the north. Below you’ll find the full representation of this process in pseudocode. player_frame_rate = get_fps() delta_time = 1/player_frame_rate velocity = Vector2.new(0, 20) object.y += velocity.y * delta_time</code></pre> Alternatively, you can just divide the velocity by the frame rate because y * 1/60 = y/60</code></pre> Let’s say our game was being run on a lower-end computer and we were getting 30 frames per second. Let’s step through our code and see what happens. Intuitively, we know that if we’re getting only 30 frames per second, our object will have to move faster each frame compared to when we had higher frame rates. This is because we have less frames to display the journey of the object’s position to our target destination, and therefore we need to increase the distance our object moves each frame. Let’s check if our code does end up following that trend. First, with a frame rate of 30 fps, our delta time will now be 1/30. When we multiply 1/30 by our velocity of 20 pixels to the north, we get 1/30 * 20 = 0.6666</code> pixels toward the north every frame. That’s double the velocity we had previously with 60 frames per second. We now know that our code works and it indeed follows the inversely proportional trend between frame rate and update speed. Static Keyword in Java – What in the world is it? Unknown — Tue, 29 Aug 2023 00:00:00 +0000 Is a question many young and naive Java developers have that often go unanswered due to overly-complicated explanations that are rather obscure, and not geared towards beginners. Here(not just this article/post but on the behalf of any subsequent tutorials), I aim to provide a quick yet effective definition of what this keyword actually means, and what it can be used for. A Quick Definition</h1> The static keyword tells Java that a method or variable in a class should be made accessible without the need of instantiation. Therefore, it becomes a part of the class. Any objects instantiated from that class will have the same value for its static variables. Example - How can I use it?</h2> Let’s create an application that categorises users into their age groups, based on their age input. These age groups consist of seniors, middle-aged, and youngsters. Let’s start by creating a class for each of them, and group them into a package just for demographics. package org.demographics; public class Senior/MiddleAged/Young { public static int ageGroup = ??; ...some more code dedicated to each class... }</code></pre> Now, let’s create the main class that will make use of these classes and make up the logic of the application itself. // Main class where we specify the logic import org.demographics.Senior; import org.demographics.MiddleAged; import org.demographics.Young; public class Categoriser { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("Enter your age"); int age = scanner.nextInt(); String ageGroup = ""; if (age >= Senior.ageGroup) { ageGroup = "Senior"; …do stuff, instantiate Senior and add to an array, etc…} else if (age >= MiddleAged.ageGroup) { ageGroup = "Middle Aged"; …do more stuff… } else if (age >= Young.ageGroup) { ageGroup = "Young"; …do more stuff… } else { System.out.println("You are too young!"); return; } System.out.println("You shall be categorised as " + ageGroup); } }</code></pre> Each demographic class has a specific age range. With the static variable, we get rid of the need to instantiate a Senior, MiddleAged, and Young class just to access their age range. Reminder</h1> Remember, we made the ageGroup variable static because: We want to be able to access it without or before instantiation, otherwise we’d have to do:</li> </ol> Senior placeholderSenior = Senior(); int seniorAgeGroup = placeholderSenior.ageGroup;</code></pre> It is clearly established for all objects created from that class, and can’t be modified for any exceptional object. We don’t want two Senior objects having an age group of 10 years old and the other 60 years old.</li> </ol> Note</h1> Do note that static variables aren’t constant(some may misunderstand it to be), rather it is consistent across all its instantiated objects. It can be changed, but the change will be reflected across all objects instantiated from it. Programming Plans for The Next Few Months Unknown — Mon, 02 Aug 2021 00:00:00 +0000 After giving a lot of careful thought and consideration, I have decided to continue my programming journey by learning more about Python(by taking on different programming challenges with native Python), learning Web Development with Flask(for now, may switch to Django) and game development with Unity 3D. First of all, I came upon this decision because of three primary reasons. I think that it’s good for me to stick to a specific language that I’m already comfortable with and improve on it I will be taking Computer Science for my O-Levels next year and it just so happens that the syllabus is more focused on webdev as the Pre-Release project is actually based on creating a web application/service. Therefore, I think it’ll be beneficial for me to have my own little side projects, so that they may prepare me for the final exams. I also happen to like creating websites. I really love creating games and I don’t think I will ever give it up. In the future, I aspire to be a hobbyist game developer while working a full-time job as either a software engineer or AI engineer. I just love the fact that gamedev is a mix of creativity(in terms of creating beautiful graphics and music), programming, story-writing and etc. Anyways, that’s the end of my short and brief update! Introduction Unknown — Mon, 26 Jul 2021 00:00:00 +0000 Hello! My name is Daniel and I absolutely adore programming. From simple console “Hello World” programs to large applications, I just love all of it. For the past few months now, I’ve been wondering, why do I like programming? Well, here are a few answers. Programming is a very rewarding and challenging hobby/profession. There’s just something about the ecstatic feeling you get when you solve a bug, or devise a concise and elegant algorithm that allows you to create whatever you want. I’ve been programming for about a year now and will from now on be using this website/blog to document my journey into the programming world so that I may one day look back upon all these projects and reminisce the hardships as well as the sweet memories and experiences. Projects and details about them will go into the Projects page whilst the development logs will be going into my Posts page. I plan to have the posts page contain both programming and life updates so that things can be a little more organised for a better viewing experience.

Windows</h2>

Next Step: Project Setup</h1>
Now that we've installed zenoh-cpp into our system, we can start to dive into setting up a project and writing our first few lines of code. You will find this in the next article</a>.</p>

</br>
</br></p>

Post list</h1>

Zenoh Introduction & Installation</a></li>
Zenoh Introduction & Installation Process Breakdown (Optional)</a></li>
Zenoh Project Setup & Sample</a></li> </ol>

Emergent Abilities of Large Language Models - Paper Summary

Emergent risks</h1>
LLMs carry societal risks such as truthfulness, bias, and toxicity. It's important we consider whether or not these risks are emergent as well.</p>

Sociological changes</h1>
We should also consider how scale affects not just the model, but the community surrounding it, how it's used, and social perception.</p>

If P then Q (Material Implication) Explained

Monty Hall Problem Explained

Controlling a Differential-Drive Robot with a Virtual Joystick

Recursive Self-Improvement (RSI)

The Role of CMake in Building Libraries - Zenoh Series

Zenoh Installation and Introduction

Zenoh Project Setup and Example

Zenoh CPP Series

Notes on Introduction to Information Retrieval, Chap. 6 (Scoring, term weighting and the vector space model)

Nonlinear Thinking - The Power of Mathematical Thinking

Notes on Introduction to Information Retrieval, Chap. 1. (Boolean Retrieval)

1.1 Boolean Retrieval Problem Simplified</h1>

C Language Cheatsheet

Website Update

The Quarrasi Lock Online: My first web-hosted application

Delta Time - The Road to Frame Rate Independence

Static Keyword in Java – What in the world is it?

A Quick Definition</h1>
The static keyword tells Java that a method or variable in a class should be made accessible without the need of instantiation. Therefore, it becomes a part of the class. Any objects instantiated from that class will have the same value for its static variables.</p>

Note</h1>
Do note that static variables aren’t constant(some may misunderstand it to be), rather it is consistent across all its instantiated objects. It can be changed, but the change will be reflected across all objects instantiated from it.</p>

Programming Plans for The Next Few Months

Introduction

Emergent Abilities of Large Language Models - Paper Summary

Emergent risks</h1> LLMs carry societal risks such as truthfulness, bias, and toxicity. It's important we consider whether or not these risks are emergent as well.</p>

Sociological changes</h1> We should also consider how scale affects not just the model, but the community surrounding it, how it's used, and social perception.</p>

If P then Q (Material Implication) Explained

Monty Hall Problem Explained

Controlling a Differential-Drive Robot with a Virtual Joystick

Recursive Self-Improvement (RSI)

The Role of CMake in Building Libraries - Zenoh Series

Zenoh Installation and Introduction

Installation</h1> Windows</h2> Prerequisites</h3> CMake</a></li> GCC</a> Has to be C++17-compliant</li> </ul> </li>

Windows</h2>

Prerequisites</h3> CMake</a></li> GCC</a> Has to be C++17-compliant</li> </ul> </li>

Building from Source and Installation</h3> In order to install zenoh-cpp, we first need to build and install zenoh-c (since zenoh-cpp is a binding around zenoh-c as mentioned above). So crack open a terminal, and run these commands!</p>

Next Step: Project Setup</h1> Now that we've installed zenoh-cpp into our system, we can start to dive into setting up a project and writing our first few lines of code. You will find this in the next article</a>.</p> </br> </br></p>

Zenoh Project Setup and Example

Zenoh CPP Series

Post list</h1> Zenoh Introduction & Installation</a></li> Zenoh Introduction & Installation Process Breakdown (Optional)</a></li> Zenoh Project Setup & Sample</a></li> </ol>

Notes on Introduction to Information Retrieval, Chap. 6 (Scoring, term weighting and the vector space model)

Nonlinear Thinking - The Power of Mathematical Thinking

Notes on Introduction to Information Retrieval, Chap. 1. (Boolean Retrieval)

1.1 Boolean Retrieval Problem Simplified</h1>

C Language Cheatsheet

Website Update

The Quarrasi Lock Online: My first web-hosted application

Delta Time - The Road to Frame Rate Independence

Static Keyword in Java – What in the world is it?

A Quick Definition</h1> The static keyword tells Java that a method or variable in a class should be made accessible without the need of instantiation. Therefore, it becomes a part of the class. Any objects instantiated from that class will have the same value for its static variables.</p>

Note</h1> Do note that static variables aren’t constant(some may misunderstand it to be), rather it is consistent across all its instantiated objects. It can be changed, but the change will be reflected across all objects instantiated from it.</p>

Programming Plans for The Next Few Months

Introduction

Emergent risks</h1>
LLMs carry societal risks such as truthfulness, bias, and toxicity. It's important we consider whether or not these risks are emergent as well.</p>

Sociological changes</h1>
We should also consider how scale affects not just the model, but the community surrounding it, how it's used, and social perception.</p>

Next Step: Project Setup</h1>
Now that we've installed zenoh-cpp into our system, we can start to dive into setting up a project and writing our first few lines of code. You will find this in the next article</a>.</p>

</br>
</br></p>

Post list</h1>

Zenoh Introduction & Installation</a></li>
Zenoh Introduction & Installation Process Breakdown (Optional)</a></li>
Zenoh Project Setup & Sample</a></li> </ol>

A Quick Definition</h1>
The static keyword tells Java that a method or variable in a class should be made accessible without the need of instantiation. Therefore, it becomes a part of the class. Any objects instantiated from that class will have the same value for its static variables.</p>

Note</h1>
Do note that static variables aren’t constant(some may misunderstand it to be), rather it is consistent across all its instantiated objects. It can be changed, but the change will be reflected across all objects instantiated from it.</p>