# Tagged Questions

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

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### Inaccurate fractional exponentiation / accurate fractional exponentiation in Python? [duplicate]

In Python, 9 ** 3 obviously is 729; why is 729 ** (1 / 3) 8.999999999999998? 9 == 8.999999999999998 gives False. Is this problem solvable?
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### Summarizing set of parameters with different weights

Not sure if this is the right place to ask this, I tried maths.stackexchange.com but didn't get much response, so I'm going to try my luck here. I've an educational game which teaches several ...
164 views

### Storing a straight line equation

How to store a straight line (infinite length, not a line segment) efficiently? This is not a duplication of How to represent a geometric line programmatically?, because the linked question is about ...
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### Choose “representative” subset out of a set of points

So I have a set of given locations (i.e. two-dimensional points) G, a set of wanted locations W and a natural number N. Assume |W| < N. I want to choose N elements of G such that the elements of ...
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### Can I find the remainder more efficiently?

Here : https://github.com/gnufinder/prime-factor I submitted a contribution with the goal to find a prime factor of the number 2222+3333. The number has 3,638,334,640,025 digits, so ECM will take ...
260 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 #...
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### Optimizing the exponential smoothing of a big array

I have a large set of values (let's say 1M entries) where I need to apply an exponential smoothing algorithm, but only incrementing one value at a time (all others decay to zero). The trivial ...
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### Achieving permutation using recursion [closed]

Though I like recursions and understand it, I fail to master it! I am stuck with a problem which I know that recursion can solve, but I do not know how. I have an array of strings like: "hundred", "...
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### How to create an algorithm for a raffle, where each raffle guarantees a winning ticket?

I am looking for an algorithm to create a raffle, where each participant is assigned a ticket with a random series of numbers. Each raffle hast N participants, and there should exist same amount of ...
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### 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) ...
245 views

### Convert version string to integer

I need to be able to convert a version string to an integer. I've decided I will follow semantic versioning so version strings will be of the type x.y.z. Initially I thought a simple algorithm like ...
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### Question about the uses of matrices in games and 3D graphics [closed]

So I know that matrices are used extensively in the field of games and 3D graphics, for example, you need to know how to do matrix multiplication if you want to understand how scaling an object works, ...
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### 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 ...
7k 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 ...
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### Are there compilers which optimize the use of mathematical functions?

Today while programming I stumbled upon the following question - are there any compilers which optimize based on mathematical assumptions? For instance in cases like unsigned int i,b; (i,b not ...
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### Should `Vector<float>.Equals` be reflexive or should it follow IEEE 754 semantics?

When comparing floating point values for equality, there are two different approaches: NaN not being equal to itself, which matches the IEEE 754 specification. NaN being equal to itself, which ...
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### How to handle user created expressions in application

In our application users can enter custom expressions to calculate certain things. For instance they can specify an invoice and define a number of lines for cost calculation. Example for a course ...
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### From a set of rules, derive the implications? [closed]

I've only just become interested in this domain, so sorry if I'm not using the correct terminologies. What I want is the following: Say I have a set of rules (or constraints), I want to derive some ...
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### Program to select N integers with constraints [closed]

I need to write a program which takes 4 inputs as follows N = The number of integers to be generated (10 < N < 10000) Start = The minimum value of the integers (100 < Start) End = The ...
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### Number of parallel lines in a given set of lines [closed]

I am given N lines, i.e, I am given a,b,c for N lines. And each line is of the form ax + by + c = 0. I need to find out the maximum number of lines that are parallel to each other. For this, first I ...
2k views

### Why does Math.min work with a one element array

According to MDN Math.min accepts only numbers, and if one of the arguments is not a number, it'll return NaN. It's true that if we pass an array with multiple numbers we get NaN, like this: Math.min([...
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### Should a generic vector class allow non-finite doubles as values?

I am currently writing an immutable multipurpose vector class in Java that essentially wraps a double[]. The class will be part of a game library, used to calculate entity positions, physics, pixel ...
7k views

### Why is Math.Sqrt() a static function?

In a discussion about static and instance methods, I always think, that Sqrt() should be a instance method of number types instead of a static method. Why is that? It obviously works on a value. // ...
156 views

### C# Abstract math classes from libraries

I'm currently writing a library that abstracts 3D rendering and uses SharpDX and OpenTK as graphics libraries. The problem is that OpenTK and SharpDX have their own implementations of Vector2, Matrix, ...
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### 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: ...
203 views

### How does google calculate travel distance/time

I've been working for quite a while now on a service that generates optimal routes for a given set of addresses and vehicles (Vehicle routing problem / traveling salesman problem). Now it's all ...
253 views

### What is the best data model to represent mathematical range (in database, xml, json…)?

For example, greater or equal to 50 and smaller than 100 (>=50 && < 100) smaller than 10 or greater than 40 (<10 || >40) I have been thinking about how to represent ...
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### Computer Algorithms for Polynomial Regression [closed]

Given a data set of arbitrary size, what algorithm would be appropriate for performing the polynomial regression on the data set such that the highest degree of the polynomial is n? If there are ...
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### How an add vertex operation could be performed in constant time for a graph represented using adjacency list?

Adding a vertex in a graph that is represented using an adjacency list takes O(1) time complexity according to http://bigocheatsheet.com/ (graph operation > adjacency list > add vertex). It is said ...
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### why adding a vertex in a graph represented using an adjacency matrix takes O(|v|^2) time complexity?

Adding a vertex in a graph that is represented using an adjacency matrix takes O(|v|^2) time complexity according to http://bigocheatsheet.com/ (graph operation > adjacency matrix > add vertex). But ...
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### In what programming language did the use of the percent sign (%) to mean modulo/remainder originate?

In what programming language did the use of the percent sign (%) to mean modulo/remainder originate? This previous post1 explains that the symbol % was likely chosen because it includes a slash, ...
283 views

### Why does Java define BigInteger / BigDecimal values of 10?

Question perhaps slightly left of field - but I'm curious as to the logic behind why Java's BigInteger/BigDecimal classes feel the need to define a constant of TEN? Example taken from java.math....
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### Error handling in math library functions

When writing a library function, such as double getAvg(double[]); how should one handle the empty array? (Note that, mathematically speaking the avg of an empty set is undefined.)
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### Fast fixed-size (256 bit) integer modulo/division

What is the fastest way to divide two 256-bit integers? They are represented as an array of 26-bit words, each stored in 32-bit integers. I have access to a 64-bit type if that's useful. It seems ...
219 views

I want to make a fairly complicated mathematical library for a personal project and then have a visualization/GUI to go along with it to demonstrate the maths - nothing hardcore like topology but just ...
319 views

### Hamming Distance using a dictionary

First time poster. I'm currently programming a hamming distance program using a dictionary. So if we start with the word "cat" and we want to transform it into "dog", the sequence is cat-->cot-->dot-...
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### Algorithm and data structure to match groups of users (1-5 each) into 2 balanced sets of 5 users

I'm building a matchmaking queueing service for a 5v5 team-based game. I have a large set of users that are grouped into unique lobbies comprised of 1-5 users each. Each user has an integer based ...
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### BCMath vs MySQL: performance

Scenario I am working on a web application that handles financial transactions, and my code will need to be reusable for everything from consumer carts to manufacturer/distributor shipments. The ...
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### 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....
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### Count amount of points for XY options (in poll) where options dont have equal amount of points

I have a code where I want to avoid using a for/each loop to count the amount of points options in poll have together. Reason is, every option has different ammount of points and I want to get number ...
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### Generating New Media Content From Binary Patterns

At the most basic level, a digital media file (document, song, video, etc) is just a rather large pattern of 1's and 0's. We can say that for any given piece of digital media, there corresponds a ...
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### Changing coordinate systems in python

I am working on a visual python program that is meant to model the orbit of an electron around the core of a Hydrogen atom. In order to avoid the singularity at r = 0 in the equation for coulomb ...
223 views

### How to iterate between these elements

I have an array of elements: int[] elem = new int[] {A, B, C}; I need to calculate the sum of ALL the combinations of those elements, where only some of the elements can be optionally selected. I ...
1k views

### Why is negative zero important?

I'm confused about why we care about different representations for positive and negative zero. I vaguely recall reading claims that having a negative zero representation is extremely important in ...
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### Vector API, naming for element-wise multiply [closed]

I'm helping develop a 3D Vector class, which has common operations such as: v = v1.cross(v2) v = v1 * v2 - infix multiply for dot product. v = v1 + v2 - infix addition. v = v1.slerp(v2) - spherical ...
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### How to selecting Teams with Minimum Difference between Knowledge Levels

For the below challenge from a programming site, I am bit confused. Problem Statement: A Professor of Physics gave projects to the students of his class. The students have to form a team of two for ...
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### System for deducting velocity against sources pf gravity

Say I have a particle-based physics engine (which I do) that uses lots of particles with a x and y coordinate and velocity. These particles can also have a mass, which means that these particles (with ...
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### Convert x and y velocity to x and y velocity relative to another point

The question I asked probably isn't very clear, so I'll explain. If I have an x and y velocity, where the y goes towards the bottom of the screen, and the x goes towards the right of the screen, how ...