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

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3
votes
3answers
4k views

0x9e3779b9 golden number

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 ...
23
votes
5answers
8k views

Return random `list` item by its `weight`

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

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 ...
0
votes
0answers
25 views

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 ...
3
votes
0answers
86 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 ...
1
vote
0answers
37 views

Can someone explain how this ruby basic-calculator code handles addition and subtraction? [migrated]

So I was working on a Codewars problem here, and found some code posted to Github that works out-of-the-box. Problem is, I don't understand how part of it works. Here are the Codewars directions: ...
8
votes
2answers
4k views

Find the new coordinates using a starting point, a distance, and an angle

Okay, say I have a point coordinate. var coordinate = { x: 10, y: 20 }; Now I also have a distance and an angle. var distance = 20; var angle = 72; The problem I am trying to solve is, if I want ...
10
votes
5answers
837 views

Interview puzzle on traveling on a line segment

On a number line of length M, where 0 < M <= 1,000,000,000, you given N (1 < N <= 100,000) integer pairs of points. In each pair, the first point represents where an object is currently ...
8
votes
3answers
1k views

What is the best way to keep track of the median?

I read a question, and I'm looking for input on how to solve it: Numbers are randomly generated and stored into an (expanding) array, How would you keep track of the median? There are two data ...
0
votes
1answer
40 views

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 ...
0
votes
1answer
21 views

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 ...
0
votes
1answer
47 views

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 ...
2
votes
2answers
197 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 ...
6
votes
1answer
2k views

Can one edit a built-in Python module?

I'm currently learning Python and I'm at the point in the book about using the Math library. I looked on the Python website and noticed the library was a bit scarce and am writing some more useful ...
0
votes
3answers
5k views

How much math do you learn in computer science? [closed]

How much do you need to know for computer science? When you get out of a PhD program in computer science at most schools how much math do you come out knowing? I'm guessing beyong the high school ...
30
votes
4answers
782 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 ...
-1
votes
1answer
120 views

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 ...
2
votes
4answers
2k views

How to get from 1 byte to 2 bytes

We have 1 byte, which is 8 bits, which is 2^8. Now 2 bytes should be 2 * 1 byte, which is 2 * 2^8 = 2^9, but actually 2 bytes is 2^16. What am I missing here? It seems like 2 bytes isn't 2 * 1 byte, ...
73
votes
26answers
23k views

What does mathematics have to do with programming?

I just started a diploma in software development. Right now we're starting out with basic Java and such (so right from the bottom you might say) - which is fine, I have no programming experience apart ...
5
votes
4answers
353 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 ...
7
votes
0answers
817 views

Math underpinnings of software testing? [duplicate]

In my software engineering course, we recently (briefly) covered testing. Over the course of the discussion some topics came up that made me wonder about the math underlying software testing (such as ...
1
vote
2answers
154 views

Line intersection detection algorithm

I'm trying to detect if a line drawn by the user intersects itself. I'm using a line intersection detection algorithm that goes through each waypoint of the line and checks if intersects with any ...
0
votes
1answer
67 views

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 ...
1
vote
1answer
30 views

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 ...
0
votes
1answer
60 views

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 ...
1
vote
3answers
197 views

Domain analysis - why OFF points are inside of the domain when the border is open

I have asked on a few other sites, no response but it must be something silly as many authors mention in their books. Here is the best text I found: My ultimate question is: Why the OFF point lies ...
0
votes
0answers
56 views

Domain analysis for discrete values - ON and OFF points in these cases

Following my previous question (with great answer from Bart van Ingen Schenau), I noticed a discrepancy I could not wrap my head around: Bart mentioned that: The point ON the boundary is by ...
-1
votes
1answer
103 views

Algorithm to 'segment' a number into blocks of n?

I'm not sure how to word the title properly, but the problem goes something like this: I have 5 nodes, and node 0 is the "master". User inputs a number, e.g. 100 to the master. master "splits" the ...
1
vote
0answers
204 views

What is the “correct” way to store functions in a database?

Note: Yes, I know that storing functions in databases should be punishable by law. We are developing a financial web application using PostgreSQL, Sinatra and AngularJS. As you may have guessed, a ...
0
votes
2answers
138 views

Why is the “period of a (pseudo)random number generator” important?

I've been trying to understand (pseudo)random number generator code from various sources and the concept of the period continues to elude me. To satisfy the minimum level of understanding, I've tried ...
2
votes
1answer
221 views

Well defined mathematical operations for bearing (angle) class

I have written a class to represent bearings (angles with a nautical theme, and a specific normalisation range). In the program, it is necessary to perform some mathematical operations on them, so ...
17
votes
7answers
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, ...
4
votes
1answer
93 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 ...
0
votes
3answers
180 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 ...
23
votes
11answers
3k 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 ...
15
votes
10answers
978 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 ...
5
votes
2answers
204 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 ...
1
vote
1answer
83 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 ...
7
votes
5answers
10k views

How to handle large numbers?

Well, I've just started doing puzzles and it's so annoying to see puzzles which are easy to do but also need to handle very large numbers. That's the problem. Say I have to deal with numbers like 10 ...
0
votes
0answers
27 views

Specific weight randomness based on a curve [duplicate]

I had a problem where I had a list of objects and I wanted the ones near the front of the list to "appear more" then the others when chosen randomly. There wasn't any specific weighting involved for ...
1
vote
1answer
78 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 ...
0
votes
5answers
414 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. ...
0
votes
1answer
363 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 ...
4
votes
3answers
1k 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 ...
4
votes
2answers
198 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 ...
1
vote
1answer
50 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 ...
3
votes
1answer
433 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 ...
2
votes
2answers
138 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 ...
-3
votes
3answers
443 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 ...
10
votes
1answer
226 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 ...