primes

Generating Prime numbers is a toy problem that I often attempt from time to time, especially when experimenting with a new programming language, platform or style. I was thinking of attempting to write a Prime Number Generation algorithm or a Prime Number Test Algorithm using Hadoop (Map Reduce). I thought I'd post this question to get tips, references, to algorithms, approaches. Although my primary interest is a Map Reduce based algorithm I wouldn't mind looking at new Hadoop programming models or for example looking at using PiCloud I have seems some interesting questions here on Prime

I have been trying to write Sieve of Eratosthenes algorithm in JavaScript. Basically I just literally followed the steps below: Create a list of consecutive integers from 2 to (n-1) Let first prime number p equal 2 Starting from p, count up in increments of p and removes each of these numbers (p and multiples of p) Go to the next number in the list and repeat 2,3,4 Add unintentionally deleted prime numbers back to the list and this is what I have come up with: function eratosthenes(n){ var array = []; var tmpArray = []; // for containing unintentionally deleted elements like 2,3,5,7,... var

I've been working on solving Project Euler problems in Clojure to get better, and I've already run into prime number generation a couple of times. My problem is that it is just taking way too long. I was hoping someone could help me find an efficient way to do this in a Clojure-y way. When I fist did this, I brute-forced it. That was easy to do. But calculating 10001 prime numbers took 2 minutes this way on a Xeon 2.33GHz, too long for the rules, and too long in general. Here was the algorithm: (defn next-prime-slow "Find the next prime number, checking against our already existing list" (

I don't know if this is possible or not, but I just gotta ask. My mathematical and algorithmic skills are kind of failing me here :P The thing is I now have this class that generates prime numbers up to a certain limit: public class Atkin : IEnumerable<ulong> { private readonly List<ulong> primes; private readonly ulong limit; public Atkin(ulong limit) { this.limit = limit; primes = new List<ulong>(); } private void FindPrimes() { var isPrime = new bool[limit + 1]; var sqrt = Math.Sqrt(limit); for (ulong x = 1; x <= sqrt; x++) for (ulong y = 1; y <= sqrt; y++) { var n = 4*x*x + y*y; if (n <=

I have perused a lot of code on this topic, but most of them produce the numbers that are prime all the way up to the input number. However, I need code which only checks whether the given input number is prime. Here is what I was able to write, but it does not work: void primenumber(int number) { if(number%2!=0) cout<<"Number is prime:"<<endl; else cout<<"number is NOt prime"<<endl; } I would appreciate if someone could give me advice on how to make this work properly. Update I modified it to check on all the numbers in a for loop. void primenumber(int number) { for(int i=1; i<number; i++) {