A primality test is an algorithm for determining whether an input number is prime.
A primality test is an algorithm for determining whether an input number is prime.
Questions tagged [primality-test]
115 questions
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Determine a prime number with right fold
I found this solution on the internet and I need some help understanding it:
isPrime' :: Integer -> Bool
isPrime' n = foldr (\x acc -> (n `rem` x) /= 0 && acc) True primes
where primes = 2 : filter isPrime' [3,5..]
A couple of things:
My…
dopatraman
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3 answers
Trial Division faster than Sieve for Primality Test?
I wrote two primality tests in python. First one is based on trial division, the second one applies sieve of Eratosthenes. My understanding is that sieve should have a smaller time complexity than trial, so sieve should be asymptotically faster.…
Jeffrey Boll
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Odd math error in Java
I'm writing a program to demonstrate Miller-Rabin probability testing in Java. The code is pretty much done...
import java.util.Random;
import java.util.Scanner;
/**
* Program to demonstrate Miller-Rabin primality testing
*
* @author Nick…
Nick Gilbert
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3 answers
What witnesses do i need for Rabin-Miller test for numbers up to 10¹⁸?
What set of witnesses is sufficient for the Miller-Rabin test to be correct for all numbers up to 10¹⁸? I know that use of primes up to 17 as witnesses suffices for n < 341550071728321.
kinokijuf
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Time complexity of this primality testing algorithm?
I have the following code which determines whether a number is prime:
public static boolean isPrime(int n){
boolean answer = (n>1)? true: false;
for(int i = 2; i*i <= n; ++i)
{
System.out.printf("%d\n", i);
if(n%i == 0)
…
user2900638
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2 answers
Primality test for numbers of form 10^n + k
I have some numbers of form 10N + K, where N is about 1000, and K is really small (lower than 500). I want to test these numbers for primality. Currently I'm using Fermat's test by base 2, preceded by checking small factors (<10000).
However, this…
Emily
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primality test function is_prime (n, k) based on Fermat Little Theorem,
I solved this question: Implement a primality test function is_prime (n, k) based on Fermat Little Theorem, where n is the number to be tested, and k is the number of bases to be used. The function should return False if n is not prime, and True if…
0
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2 answers
Java: read an int and check its primality. If it's not prime, repeat, but max x times
Sorry for such a question, but I just can't get through to it why the following code is not working
as it is supposed to.
As written in the title, a user should enter an integer for the code to check if it's prime.
If it is not, the user gets to…
0
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2 answers
Why does my primality test stop after 1 and not seem to be able to go on?
I apologize if this is a dumb question, I'm pretty new to Java, but I can't figure out why my mod operator based primality test for numbers 1-100 stops at 1. I've tried following my code and I don't understand why it fails to continue to the last…
0
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3 answers
Converting isPrime() Python to Haskell
I have a working (albeit inefficient) function to check if a number is prime in Python and I'd like to convert it to Haskell. Efficiency doesn't matter to me right now as I am focusing primarily on making a readable algorithm in Haskell that uses…
Prithvi Boinpally
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What is the best algorithm to determine if N is a prime number (if N is [2 <= N <= 2^63-1])?
I tried using the Miller-Rabin algorithm, but it can't detect very large numbers.
#include
#include
#include
long long mulmod(long long a, long long b, long long mod)
{
long long x = 0,y = a % mod;
while (b >…
AB3
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0 answers
Why does python skip my while loop in my primality test when I enter a huge number?
I'm currently trying to make a simple primality test using python to test prime number.
Here is the code I've made for the test:
def is_prime(n):
if np.mod(n, 2) == 0:
return False
f = 3
while np.square(f) <=…
The 2nd
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Miller-Rabin Primality Test in python: Why I keep getting decimal.Overflow: []?
I was trying to do the Miller-Rabin Primality Test in python. I've written the code like below based on pseudocode on Wikipedia:
from math import *
from numpy import *
def Miller_Rabin(n, k): #Miller-Rabin Primality Test
if n == 2 or n ==…
The 2nd
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0
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1 answer
Why do we check i <= sqrt(n) to find if a number is prime or not?
I know this question has been answered before, but I didn't quite understand the explanation that was given on that question.
I was doing the 30 days of code on HackerRank, and one of the exercises was to check whether a number is prime or not.…
João Almeida
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0
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0 answers
Testing for primality on a large integer that is stored as a string in C++
I have a program that calculates large numbers by storing them as strings, so that I can have very large digits that extend beyond long long.
I can add the strings using a function I've written that models how we humans do addition by hand on paper,…
moreQthanAs
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