# Questions tagged [random]

This tag is for questions dealing with random numbers, pseudorandom numbers, and computer entropy.

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### How should I test randomness?

Consider a method to randomly shuffle elements in an array. How would you write a simple yet robust unit test to make sure that this is working? I've come up with two ideas, both of which have ...
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### I'd like to write an "ultimate shuffle" algorithm to sort my mp3 collection

I'm looking for pseudocode suggestions for sorting my mp3 files in a way that avoids title and artist repetition. I listen to crooners - Frank Sinatra, Tony Bennett, Ella Fitzgerald etc. singing old ...
• 689
1 vote
2k views

### How to generate random numbers with a (negative) sloping distribution?

Given a maximum integer value M, I want to generate N integer values that are distributed with a lower frequency when approaching M (preferably M should still have a non-zero probability). I don't ...
• 1,140
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### What are best practices for testing programs with stochastic behavior?

Doing R&D work, I often find myself writing programs that have some large degree of randomness in their behavior. For example, when I work in Genetic Programming, I often write programs that ...
10k views

### Unit-testing of inherently random/non-deterministic algorithms

My current project, succinctly, involves the creation of "constrainably-random events". I'm basically generating a schedule of inspections. Some of them are based on strict schedule constraints; you ...
• 21.9k
1 vote
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### Unevenly distributed random number generation [duplicate]

Let's say I have to generate random number from 1 to 100, however, the probability of each number is not 1/100, but a predefined probability. How to generate that number? I use Ruby/Python.
• 325
13k views

### How do functional languages handle random numbers?

What I mean about that is that in nearly every tutorial I've read about functional languages, is that one of the great things about functions, is that if you call a function with the same parameters ...
• 1,455
54k 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 ...
• 691
134k views

### UUID collisions [closed]

Has anybody done any real research on the probability of UUID collisions, especially with version 4 (random) UUIDs, given that the random number generators we use aren't truly random and that we might ...
• 1,939
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### Can you use Pi as a crude random number generator?

I recently saw this question over at math.SE. It got me thinking. Could Pi be used as a crude random number generator? I mean the results are well known(how long has pi been computed to now?) but, Pi ...
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### 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 ...
• 163
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### Why do we need a seed in Random Number Generators?

I want to know how Random number generator(RNG) works in any PL(Programming language). I know the random methods has short periods. i.e they start repeating the values after specific number of time. ...
• 187
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### Unit testing methods with indeterminate output

I have a class that is meant to generate a random password of a length that's also random, but limited to be between a defined min and max length. I'm constructing unit tests, and ran into an ...
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### Find out whose turn it is to buy the croissants, accounting for possible absences

A team has decided that every morning someone should bring croissants for everybody. It shouldn't be the same person every time, so there should be a system to determine whose turn it is next. The ...
2k views

### How to create a random generator

How could a random generator be implemented? I'm not speaking about the invocation of a language mathRandom() method, but the implementation of the routines that lead to generate numbers totally ...
• 287
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### Which of these two shuffle algorithms is more random?

Which of below two shuffle algorithms (shuffle1 and shuffle2) is more random? public final class Shuffle { private static Random random; public static void shuffle1(final Object[] array) { ...
• 133
1 vote