# Questions tagged [math]

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

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### Transpose a matrix without a buffering one

How is it possible to transpose a MxN matrix without using a "buffering" matrix? In the latter case it's easy and quite the "classic" approach... Given a matrix[M][N], I would like to put it into a ...
543 views

### Mathematically correct A* heuristic / distance estimator for a latitude / longitude graph

I have a graph in which each node is a geographical point on the surface of the earth, defined by it's latitude / longitude coordinates. Correct ways to calculate the distance between two such points ...
7k 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 ...
280 views

### Algorithm to find the fewest number of values (from a set of values) where the sum equals a value (+ one more condition)

The simplest way to explain this is with an example. You're given then number 19 and you have a set of numbers to choose from: 1, 2, 3, 4, 6 When choosing values from the list (which can be ...
145 views

### Program to find Orthogonal Matrices

I have been trying to find orthogonal matrix of order n where first row will be given as 1/√n, 1/√n, .... n times. The second row will be a vector such that dot product of it with the row above and ...
3k views

### Given a number which is power of 2, check if it is even power or odd power

I am given a number n , which is always a power of 2. I want to check whether n is odd power of 2 or even power of 2. For example: n=4 , ans= even n=8, ans=odd (because 8 is 2^3) n=1024 , ans=even. ...
508 views

### When should a trig function, with a degree argument, return -0.0?

In creating trig functions my_sind(d), my_cosd(d), my_tand(d), that used a degree argument rather than a radian one and provided exact answers at multiples of 90, I noticed that the result was ...
2k views

### What can one do to improve readability of math-oriented code in C#, Java, and similar? [closed]

As both a C programmer and a C# programmer, one of the things I don't like about C# is how verbose math functions are. Every time you would have to use a Sin, cosine, or power function for example, ...
287 views

### Decimal vs. Integer; Given a fixed range of values, which is preferable for accurate computation?

After getting into a "heated discussion" with someone, I figured I'd ask this question for the sake of posterity. I'm willing to be corrected if my assumption is incorrect but I'd like to hear a ...
57 views

### Create a collection with “average points” of N items from a pool with items of various points

Let's say I have a question pool to generate exams out of it. Each question contains a difficulty from 1 (hard) to 99 (easy). The questions are available in a hash / array (adapt to your favorite ...
623 views

### How can I make sense of the word “Functor” from a semantic standpoint? [closed]

When facing new programming jargon words, I first try to reason about them from an semantic and etymological standpoint when possible (that is, when they aren't obscure acronyms). For instance, you ...
375 views

### Implied precision of floating-point functions

While reviewing another programmer's implementation of a function to calculate the normal distribution CDF, I made a suggestion to either replace the entire implementation with Python's built-in ...
422 views

### Representing the hierarchy of groups of numbers using type inheritance

I've run into an interesting conundrum while coding my own implementations for the basic sets of mathematical numbers (Natural, Integer, Rational, Irrational, Real, Complex). I'm doing this mostly for ...
383 views

### Why are floats called “real numbers” in some languages?

Some programing languages, notably Pascal, have a type of numbers called "real". However, mathematically speaking, these types aren't real. For them to be "real", these types have to be able to ...
2k views

### Is Haskell appropriate for Signal Processing, Communication Systems and Information Theory? [closed]

I have been working on Software-Defined Radio projects for almost a year. This is an area which requires lots of signal processing (digital filters and FFTs), communication theory (modulation, ...
338 views

### Is hadoop designed only for “simple” data processing jobs, where communications between the distributed nodes are sparse?

I am not a professional coder, but rather an engineer/mathematician that uses computer to solve numerical problems. So far most of my problems are math-related, such as solving large scale linear ...
1k views

### Why did Shannon's outguessing machine beat Hagelbarger's?

I'm reading "Rock Breaks Scissors", which describes two "outguessing machines" built at Bell Labs that try to exploit human non-randomness in the game of matching pennies. There was an outguessing ...
1k views

### Fiscal quarter vs calendar quarter

I'm building a Date/Time class with a "configurable quarter" system as follows. User specifies which month the quarter starts at (config) Set of functions to deal with quarters (next quarter, prev ...
50 views

### Time passage arithmetic explanation

I ported this from http://www.effectgames.com/effect/article.psp.html/joe/Old_School_Color_Cycling_with_HTML5 some time ago. However i'm now wanting to modify it for the purpose of changing it from ...
112 views

### Is there an easy way to type in common math symbols?

Disclaimer: I'm sure someone is going to moan about easy-of-use, for the purpose of this question consider readability to be the only factor that matters So I found this site that converts to easting ...
343 views

### If a library doesn't provide all my needs, how should I proceed? [closed]

I'm developing an application involving math and physics models, and I'd like to use a Math library for things like Matrices. I'm using C#, and so I was looking for some libraries and found Math.NET. ...
3k views

### Japanese Multiplication simulation - is a program actually capable of improving calculation speed?

I'd like to write a simulation of Japanese Multiplication to get benchmarks on large calculations utilizing the shortcut vs traditional CPU multiplication. I'm curious as to whether it makes sense to ...
352 views

### Unique ID algorithm

I've got a route that contains objects. Each one has value 0 or 1. I need unique route ID which will identify any objects order. Currently I'm doing it using binary number that is converted to decimal ...
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 ...
147 views

### Why Num&sizeMinusOne faster than num&(size-1)

I've been told that when I have a hash table of size m and m=2^k, I can use the & operator as num & (size-1) instead of num % size, to fit the hashCode to my table size. I've also been told ...
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 ...
675 views

### Euclidean Space Fully Connected Nondirectional Graph: Shortest Path to all nodes

So this may be a question that is born of my inability to properly express my intentions to Google. In a fully connected non-directional graph such that any three points can be properly represented ...
3k views

### Representing a deck of cards in C (not C++)

So far my best ideas have been as fallows A) Represent a "card" in one structure and have a "deck" in another a deck being an array of 52 cards and a card being 2 chars one for and rank one for suit. ...
788 views

### Progress bar for unknown number of items

I am working on a survey-based feature in our application and the survey has branching points at any given question depending on the answer given. Each path that a branch can take may not have the ...
438 views

### Capture portions of a number using mathematical operations [closed]

Is there a mathematical way to get the following: For the the number 777,888,999 so 777 million and etc etc getMillions(777888999) should return 777 only getThousands(777888999) should return 888 ...
793 views

### Find possible variations of one item out of multiple baskets.

I have three baskets of balls and each of them has 10 balls which have the following numbers: Basket 1: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Basket 2: 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 ...
2k views

### What are the essential mathematics topics that a programmer should know in order to learn algorithms? [closed]

Being a electronics engineer, I was never exposed to any algorithms. Now I am a experienced programmer and want to learn Algorithms. I started with CLRS. But I was overwhelmed by the maths in the book....
641 views

### What rationale is used when programming language designers decide what sign the result of modulo operation takes?

Going through Modulo operation (the avenue I entered while exploring the difference between rem and mod) I came across: In mathematics the result of the modulo operation is the remainder of the ...
12k views

### Why do we still use floats? [duplicate]

I understand why floats served a purpose in the past. And I think I can see why they're useful in some simulation examples today. But I think those example are more exceptional than common. So I ...
870 views

### How do you program a way to create mathematics formulas?

For one of my project ideas, I want to create a dice rolling app. It would allow people to setup somewhat complex combinations of dice roll cascades in a visual way. I have a pretty good idea on how ...
3k views

### How to represent a geometric line programmatically?

I have been trying to design a library to do some simple geometric computations in an Euclidean space regardless of its dimension. While it is easy to represent points, vectors, hyperspheres and ...
222 views

### shall a vector2 extends a vector3 or is it the opposite?

Perhaps the question might be tied to a theoritical or mathematical forum, but since it is for programming purpose, i ask here first: In a computer vision context, i write a couple of interfaces ...
468 views

### Can relational algebra/calculus proofs be used to test/verify SQL?

Is it feasible or even possible to use relational algebra and/or relational calculus in the form of proofs to test/verify the correctness of SQL statements, functions, and stored procedures? It seems ...
2k views

### Fastest way to check if two square 2D arrays are rotationally and reflectively distinct

The best idea I have so far is to rotate first array by {0, 90, 180, 270} degrees and reflect it horizontally or/and vertically. We basically get 16 variations  of first array and compare them with ...
667 views

### Matching users based on a series of questions

I'm trying to figure out a way to match users based on specific personality traits. Each trait will have its own category. I figure in my user table I'll add a column for each category: id name ...
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 ...
1k views

### Effective and simple matching for 2 unequal small-scale point sets

I need to match two sets of 3D points, however the number of points in each set can be different. It seems that most algorithms are designed to align images and trimmed to work with hundreds of ...
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 ...
1k views

### Maths needed to understand theory behind Haskell's type system?

Recently, I've become deeply interested in Haskell. While attempting to learn new concepts (e.g. the forall keyword and ST monad) and Haskell's type system in general, I continually run into ...
51k 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 ...
1k views

### Sort rectangles in a grid based on a comparison of the center point of each

If I have a grid of rectangles and I move one of the rectangles, say above and to the left of another rectangle, how would I resort the rectangles? Note the rectangles are in an array, so each ...
2k views

### Subtractive color mixing algorithm

Here is my problem: I have a set of 'n' colors including the primary colors and their codes in hexadecimal. Now given another color 'x' I wonder if it's actually possible to come up with a mix ...
714 views

### More Accurate Random in C [closed]

I have 3 IPs and every IP has a weight, I want to return the IP's according to its weights using the random function. For example if we have 3 IP's X with weight 3 Y with weight 3 and Z with weight 3 ...