Primes or prime numbers are numbers which are divisible only by themselves and one: 2, 3, 5, 7, 11, ...
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0answers
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-1
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0answers
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4
votes
5answers
323 views
3
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2answers
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List primes within an interval
I'm trying to solve the SPOJ primes problem:
Peter wants to generate some prime numbers for his cryptosystem. Help
him! Your task is to generate all prime numbers between two given
numbers!
...
1
vote
1answer
46 views
Speeding up prime factorization
I have written the following code for returning the list of prime factors. Any speed-enhancing suggestions?
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10
votes
4answers
1k views
Wow that's a big integer! What's its largest prime factor?
I see that there are a few other people who have tackled Project Euler Problem #3. I hope you're not all sick of that question yet. I've not taken a look at those yet (purposely), but am about to now. ...
12
votes
4answers
525 views
Unit Testing for isPrime function
I've decided that I want to take a stab at test first programming. So, before I tackled writing an isPrime function, I wrote this unit test. It's my first and I'm ...
4
votes
1answer
53 views
Computation for finding the largest prime factor of 600851475143 is slow
I implemented the following for Project 3 in Project Euler:
...
5
votes
2answers
83 views
Finding prime numbers in a range
Finding the prime numbers between two given integers in the minimum number of comparisons:
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2
votes
2answers
36 views
Replacing an F# loop over a mutable variable by an immutable approach
Consider:
let mutable m' = m
while m' % i = 0L do
m' <- m' / i
I've refactored it into:
...
10
votes
3answers
589 views
Finding largest prime factor from inputted number
This is my first C# console application. This program asks for an input of a number, and finds the highest prime factor of that number. Please review my code.
Have I used things right?
Is my code ...
4
votes
1answer
52 views
Is this a good Ruby implementation of Prime Factorization?
I'm doing some practice problems on Khan Academy. The current one is Prime factorization. I came up with this:
...
4
votes
3answers
141 views
Modified Sieve of Eratosthenes has very long runtime
I am slowly moving through Project Euler, and have reached problem #10:
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million.
I did a naive ...
3
votes
0answers
51 views
Generating prime numbers using Sieve of Eratosthenes with CUDA
I'm learning CUDA and wrote a little program which generates prime numbers using the Sieve of Eratosthenes. (I know the limitations of CUDA, specially with memory sizes and limits, but this program is ...
10
votes
4answers
288 views
Threshed and Malachi'd: Sieve of Eratosthenes
I took a little bit from all the answers to my previous question Threshing: Sieve of Eratosthenes.
This may be bordering on code-golfing, but I think that I have a pretty good piece of code here.
...
5
votes
4answers
376 views
5
votes
4answers
363 views
Threshing: Sieve of Eratosthenes
I would like a complete threshing of this code so that I can see what I did wrong and what I am using incorrectly.
I made this super simple, trying to learn a little bit about ...
3
votes
2answers
639 views
Faster way to get all primes between 0 - n
Is there a faster way to get all primes between 0 - n
...
2
votes
1answer
42 views
Custom module of common functions
I got sick and tired of writing certain functions over and over again, so I made a module that has those functions whenever I need them. I don't use it for code I plan on sharing, so I don't need to ...
9
votes
4answers
2k views
Is_prime check in Python: can this be more pythonic?
I have the following function that checks if a number is prime:
...
7
votes
2answers
102 views
Largest Prime Factor redux
There have been a number of questions asking for comments on code for the Project Euler problem to compute the largest prime factor of a number. A primary intent of this task is to find the factor as ...
4
votes
2answers
210 views
Submitting a Java program which implements the Sieve of Eratosthenes
I would like some feedback on a Java program which implements the Sieve of Eratosthenes to find prime numbers. Some of the 'features' I've included in the program include:
It uses a ...
10
votes
1answer
309 views
x64 Assembly - checking for largest prime factor
Using x64 assembly, I solved the Largest Prime Factor problem on Project Euler.
The problem is as follows:
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of ...
7
votes
4answers
318 views
A Fast Approach to Prime Number Sieving (Non-Threaded Array)
I am posting this question for input on comparisons between other sieving methods and opinions on what I have discovered. I believe this might be the fastest (singular, non-threaded) array ...
9
votes
5answers
502 views
Prime Number Sieving Algorithm
Edit:
Newly Updated Code here A Fast Approach to Prime Sieving (Array Implementation - Non-Threaded)
Original Thread
Last semester in my Masters Program I developed this code for sieving.
Is this ...
5
votes
3answers
102 views
Calculating the ranks of classmates' exam grades
The questions from hackerearth:
Geeko is in worry now because an exam is coming up and he has to know
what rank he can get on exams. So he goes back into the the school records
and finds the ...
10
votes
1answer
97 views
Sieve of Atkins algorithm
I got the inspiration to write this algorithm from this question. The OP cited the Sieve of Atkin as one of the fastest ways to generate primes. So I figured I would give it a try:
...
4
votes
1answer
67 views
Checking for Prime Numbers [closed]
def is_prime(n):
if n % 2 == 0 and n > 2:
return False
return all(n % i for i in xrange(3, int(math.sqrt(n)) + 1, 2))
The code works fine for a ...
6
votes
2answers
134 views
Prime Number Speed
I know prime number programs have been beaten to death. I am have been programming for eight years (not that long, but I'm not in my 20s yet and I got a programming job straight out of high school so ...
1
vote
4answers
643 views
5
votes
3answers
220 views
Psycho and ordinary numbers
The problem statement can be found here. In short, here's what the problem is about:
You're given a set of numbers and you need to find whether the the numbers are ordinary or psycho. For a number ...
5
votes
1answer
370 views
Sieve of Eratosthenes - Standard and Optimized implementation
I am a Java developer who is taking Python for the first time.
I'm sure this is not at all elegant since I am thinking more in C syntax.
...
4
votes
2answers
66 views
Reduce Prime Sieve Memory Consumption 2
I've made a prime number generator (for Project Euler). It uses Euler's Sieve (a modified Sieve of Eratosthenes), with a mod 30 step. I'd like to reduce the memory consumption to 4/15 what it ...
3
votes
2answers
165 views
Reduce Prime Sieve Memory Consumption
I've made a prime number generator (for Project Euler). It uses Euler's Sieve (a modified Sieve of Eratosthenes), with a mod 30 step. I'd like to reduce the memory consumption to 4/15 what it ...
6
votes
1answer
92 views
Make Project Euler 27 solution idiomatic Ruby
I learned to program in Java and C# and in my free time I am using Ruby because it is fun. Unfortunately I have the feeling that I write Ruby code like I am making Java or C# code. I have learned to ...
7
votes
3answers
176 views
Parallel sieve of Eratosthenes, version 2
This question is a revision of Parallel sieve of Eratosthenes. The goal is to implement a sieve of Eratosthenes with parallel strikes out from the boolean array. I tried to fix the data races and all ...
2
votes
1answer
86 views
Project Euler 27 - Quadratic Primes
Project Euler problem 27
I decided to try simple brute force, and it worked surprisingly quickly. How can this be optimized?
...
21
votes
5answers
1k views
Parallel sieve of Eratosthenes
For the first time, I tried to use threads by myself in order to implement a parallel sieve of Eratosthenes. The trick is that each time a prime is found, a thread is spawned to eliminate all the ...
9
votes
8answers
947 views
Project Euler #3 - largest prime factor
I was going through the Project Euler problem #3 and made a program to solve it. The problem is as follows:
The prime factors of 13195 are 5, 7, 13 and 29. What is the largest
prime factor of ...
10
votes
3answers
903 views
13
votes
4answers
1k views
Prime Number Generator - Are the conventions proper?
I am slowly learning C and C++, and decided after a few lessons to dive in myself without any help. I developed this Prime Number generator. It seems fast, but I'm wondering if I'm following the best ...
3
votes
2answers
264 views
Prime generator program SPOJ time limit exceed
Problem Statement
Input
The input begins with the number t of test cases in a single line
(t<=10). In each of the next t lines there are two numbers m and n (1
<= m <= n <= ...
10
votes
4answers
792 views
Sieve of Eratosthenes in C++
I'm looking for some feedback on my implementation of the algorithm. How can I improve it? I ran into problems when calculating the larger prime numbers > 46349 due to integer overflow, but fixed that ...
17
votes
5answers
874 views
Count distinct primes, discarding palindromes, in under 2 seconds
Problem Statement
Generate as many distinct primes P such that reverse (P) is also prime
and is not equal to P.
Output:
Print per line one integer( ≤ 1015 ). Don't print more than
...
11
votes
2answers
864 views
First prime number larger than given integer
How can I test this C program for "efficiency"? The most interesting usage is that it returns negative output for large enough input, otherwise the behavior is about expected. Will you suggest how to ...
7
votes
2answers
228 views
Prime generator from one to n
My code calculates primes from one to n. I have verified that the code always produces all the primes in that range correctly.
Are there any optimizations that I can make? Are there any bad ...
10
votes
2answers
390 views
First attempt at generating prime numbers
I had to look up some other solutions online because I could not figure it out on my own, which kinda sucks. I really wish I came up with it completely on my own but that didn't happen. Nevertheless, ...
7
votes
5answers
488 views
Ten thousand and first prime checker takes a very long time
I am attempting problem 7 on Project Euler. I have come up with this solution which works fine for finding smaller nth prime numbers, but really lags when it comes to higher nth prime numbers. I am ...
4
votes
3answers
135 views
Prime number util class
A prime number util, which provides 3 APIs - find the nth prime, find the next prime, and find all primes up to n.
I must admit this code has been influenced a lot by discussions here. I'm ...
5
votes
6answers
313 views
Speeding up my implementation of Project Euler #3
Project Euler problem 3 asks for the largest prime factor of 600851475143.
I have gone from 96 lines to 17 lines taking hits at this one. This is what I am left with after all of that effort:
...
