# Questions tagged [math]

Programming questions that are significantly affected or best defined by the underlying mathematics of the problem.

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1answer
147 views

### Big-O Notation and Calculus [closed]

I was wondering if there are any calculus relationships implicit in Big-O notation. For example, an algorithm linear according to Big-O notation reduces the size of the problem by a constant amount ...
10answers
14k views

### Is it good practice to replace division with multiplication when possible?

Whenever I need division, for example, condition checking, I would like to refactor the expression of division into multiplication, for example: Original version: if(newValue / oldValue >= ...
1answer
40k views

### Treating a 1D data structure as 2D grid

I am working with a native class that represents a 2D image as a 1D array. If you want to change one pixel, for example, you need to now how to derive the index from the x,y coordinates. So, let's ...
1answer
102 views

### Generic way to describe data synchronization between systems?

Is there a generic way (useful formalisms) to think about data synchronization between two systems, especially in the case of slightly asymmetric roles (eg, one system contain master data, another one ...
3answers
126 views

### What effects does memory space have on bitwise shifts?

It is true that the bitwise left shift operation (shl) doubles the value of the integer being shifted. However, when constrained to a finite space, such as 8 bits for example, left shift will begin to ...
1answer
81 views

### Gerstner Wave equation from tessendorf paper, mesh penetrates itself

I have been learning to create water waves in a mesh from a paper commonly known as the Tessendorf paper. Which is quite well known. But those who don't know this is the equations it mentions in the ...
1answer
62 views

### Best way to encode a queryable number to another unique queryable number? (database outsourcing)

So lets say you want to outsource your database to a third party and be able to query on it on their server but you want to "encode" the salary column of the users on their server, aka hide the real ...
1answer
114 views

### Find two horizontal lines to minimize distance to scattered points

I am having trouble with a coding question that I found practicing for a interview: A scatter graph of points on a page, draw two horizontal lines (these lines are parallel) across the page such that ...
4answers
5k views

### How do deal with angle wraparounds when comparing them?

Angle A is a degree angle that keeps increasing by increments and Angle B is the stopping point of Angle A (think 'Spin-the-bottle' where Angle A is the current angle of the bottle Angle B is the ...
5answers
40k views

### get weighted random item

I have, for example, this table +-----------------+ | fruit | weight | +-----------------+ | apple | 4 | | orange | 2 | | lemon | 1 | +-----------------+ I need to return a random ...
0answers
201 views

### Division by zero Java [closed]

The behavior of Java is explained in this topic. But, is Infinity useful for something? Float: public class DivisionByZeroFloat{ public static void main(String[] args) { System.out....
4answers
138 views

### How to properly decide what is the appropriate rounding off error for a mathematical function?

In the space of 3D geometry, I need to compute the magnitude of the cross product of two Line3D because I want to check whether these two Lines are "parallel" to each other. Line3D is consisted of 4 ...
5answers
17k views

### Will a computer attempt to divide by zero?

We all know 0/0 is Undefined and returns an error if I were to put it into a calculator, and if I were to create a program (in C at least) the OS would terminate it when I try to divide by zero. But ...
1answer
106 views

### Simplistic non-secure example of public key encryption

I'm giving a lecture to novice developers on security and would like to explain ssl and the basics of certificates. For this I would like to convey a vague intuitive understanding of asymmetric key ...
3answers
1k views

### Randomized Hash function with no collisions

Related to the question Which hashing algorithm is best for uniqueness and speed? Is there a way to create a hash function, or find one, whose hash length depends completely on the input length, has ...
1answer
87 views

### Where are mathematical equations applied in the application stack [closed]

Say I have a program using Java or C, that will interface with a hardware device and either read streaming data or write it to a database before applying a few complex mathematical equations to this ...
1answer
91 views

### How do I create a comparable checksum of a number sequence?

Sorry if the title is confusing, but here's an example to illustrate what I'm trying to accomplish. I would like to create a 'checksum' or ID grouping of similar number sequences, so that when you ...
5answers
2k views

### Are there any formalized/mathematical theories of software testing?

Googling "software testing theory" only seems to give theories in the soft sense of the word; I have not been able to find anything that would classify as a theory in the mathematical, information ...
1answer
113 views

### Interdependent variables

Let's say there are two variables a & b, both a & b would have a value between a predefined range. a = x1 to y1 (range) b = x2 to y2 (range) Variable a & b are interdependent, if the ...
1answer
117 views

### How a Proof Assistant Proves ∀ or ∃

Wondering how a proof assistant such as Coq proves forall or exists. For example: Three aspects: If you were to give it a huge set of items like a million, wondering if it would actually iterate ...
11answers
2k views

### How is fundamental mathematics efficiently evaluated by programming languages?

As I get more and more involved with the theory behind programming, I find myself fascinated and dumbfounded by seemingly simple things.. I realize that my understanding of the majority of fundamental ...
5answers
3k views

### Which programming languages doesn't use operator precedence besides Lisp like languages? [closed]

And what do you think about operator precedences? Would be harder programming in a language where the operations are executed in sequential order? Ex.: 2 + 3 * 4 == 20 2 + (3 * 4) == 14 Ok, Lisp ...
1answer
67 views

### Identify sets differing by one

I have a set of objects with different attributes; e.g. a set of cars with colors, brand etc. I choose subsets by virtue of a specific set of attributes. Now I want to identify pairs of such subsets ...
1answer
43 views

### Algorithm: Identify same Outlets / Supermarkets

We have a database with stores Outlets / Supermarkets (mainly in germany but other countries are also possible). We store some informations of this outlets / supermarkets like name, street, ...
1answer
505 views

### Algorithm for windowed online covariance

I'm trying to adapt an algorithm to calculate covariance to work over a rolling window on the data. Wikipedia has an algorithm for online covariance: def online_covariance(data1, data2): mean1 = ...
5answers
1k views

### Does any programming language use variables as they're in maths?

In maths, a variable means you can put any number there, and an equation will still be true: root(square(x)) = abs(x) In programming languages, this is not so: a var can change. In Python: y = (x**...
3answers
1k views

### How to use units for a slope calculation?

Simple question: is the result of a slope calculation in Python (say, stats.linregress() function) in units of radians, or unitless (e.g. what's 18 deg or 0.314 rad would be equivalent to 0.2 in the ...
1answer
477 views

### How can unums emulate IEEE's negative zero?

I am currently reading "The End of Error - Unum Computing" by John Gustafson (Youtube). What I am still not sure about is how the cases handled in IEEE by negatively signed zero are handled with unums....
1answer
1k views

### Swapping variable values without creating a new one

Recently, I was faced with a question that asked me to swap variable values without creating an extra variable. i.e. A = 10, B = 20. How store 20 to A and 10 to B? The solution is: A = A + B #...
2answers
261 views

### How to model infinite non-linear combination? [closed]

Let L be an ordered set of positive integers (for example, the set of all primes). Here, #L = infinity, and N is a positive number serving as an upper limit. Goal is to list the following set M: M =...
3answers
126 views

### Use case, design, and how to append to an immutable object in functional programming

This is not (supposed to be) an opinion question, but it is a newbie question, so if there is just a resource I haven't found that I need to read, point me there :) I am in the design stages of a ...
2answers
163 views

### Handling behavior of non-finite numbers

Without using big int classes in C++, what's a good way to handle arithmetic on large numbers? For instance, writing a Vector class that deals with dot products and cross products using large ...
1answer
288 views

### Round robin, balanced home/away, multiple locations with multi-team options

This is my first question on this forum, have tried to exhaust every possible research option I could think of or find. Actually this is the first time I've posted for help with this anywhere, so ...
1answer
671 views

### What's the needed math for building algorithms? [closed]

What's the needed math for building algorithms? Because I was reading a book and I can't understand much. It says I need simple math from high school. I don't want to learn all the math that exist ...
4answers
9k views

### TEA algorithm constant 0x9e3779b9 said to be derived from golden ratio, but the golden number is 1.618?

I'm trying to understand a constant 0x9e3779b9. What kind of data is this? It's not binary, not decimal, what is this? It's a constant used on the TEA algorithm. It says it's derived from the golden ...
1answer
1k views

### Best way to define 'snap points' between two arbitrary objects in 3D?

I'm working on a simple in-browser 3D model constructor using THREE.js. The user picks a plane body, and adds wings, cockpit, tail etc of their choice, choosing from multiple options. I need to be ...
1answer
128 views

### Memoization in case of recursive interdefined functions in Haskell/Functional Programming?

I was reading Memoization with recursion which tells how for a recursively defined function fun we can do memoization by: -- Memoization memoize f = (map f [0 ..] !!) -- Base cases g f 0 = 0 g f 1 = ...
1answer
254 views

### I loved developing a 2D game(C++ SDL), but i am not good at maths/physics [closed]

I developed 2 games in C++ using SDL. Without using any wrappers. I literally loved and enjoyed every part of the journey. Complex algorithms, how 2D works, rendering, audio, input etc. But i am not ...
1answer
71 views

### Set of items closest to the mean? [closed]

Given a set of N objects with assigned weights, how would we find the set of K objects that is closest to the average? The average being sum(weights) / N. Also, how could we compute the next set ...
3answers
844 views

### In Java, why does Integer.MIN_VALUE == -Integer.MIN_VALUE

Quite simply, I was aghast when I discovered one of my unit tests was failing because -Integer.MIN_VALUE == Integer.MIN_VALUE! Why would the language designers choose this, what is the mathematical ...
4answers
11k views

### Handling extremely large numbers in a language which can't?

I'm trying to think about how I would go about doing calculations on extremely large numbers (to infinitum - intergers no floats) if the language construct is incapable of handling numbers larger than ...
1answer
80 views

### How is the problem NOVICE43 on Sphere Online Judge(SPOJ) related to Bell Numbers?

Problem Statement : When I first learned backtracking I made a program to find all the permutations of the English alphabets in lexicographically increasing. Filled with elation I showed the ...
3answers
326 views

### What's the proper class hierarchy to use for matrices?

I'm working with particular classes of matrices which admit fast operations without resorting to dense linear algebra. To keep the heierarchy simple, I'm currently doing the following (greatly ...
1answer
1k views

### How to modify ELO algorithm when number of games is low to reduce outliers

I've developed the standard ELO implementation that can be found here, but the problem I'm running into is that my players will only have between 10 and 40 games in a "season". Since my first season ...
2answers
231 views

### How do I unit test nuanced mathematical procedures?

I'm writing some code for a scientific simulation and I'd really like to use this as an opportunity to get some unit testing practice under my belt. I understand the idea of tests in theory, but I ...
1answer
94 views

### Find transformation function for point on an image

I am trying to develop an algorithm, but I barely can describe it so I'm not sure what to look for. I have two images img_A and img_B. img_A is the original, while img_B is an image of the same item ...
3answers
28k views

### what is a efficient way to find repeating decimal

I am trying to find a efficient algorithm in Java to find the repeating decimal part of two integers a and b where a/b. eg. 5/7 = 0.714258 714258.... I currently only know of the long division ...
3answers
2k views

### What are the advantages of matrix multiplication over individual variables (graphics)?

I am learning OpenGL and the tutorials (1, 2) I'm reading teach me that to scale/rotate/translate an object you have to know matrix multiplication. Why? Instead of 3x3 matrix you can use 6 floats: ...
10answers
42k views

### How to check if 4 points form a square?

Assume I have 4 points (they are 2-dimension), which are different from each other, and I want to know whether they form a square. How to do it? (let the process be as simple as possible.)
2answers
568 views

### How to improve timeout value dynamically?

I'm working on an application where I want to keep a timeout value computed dynamically using a moving average of say 100 previous response times for service A. This value + some buffer (~3 seconds) ...