https://github.com/ppetr/zillion-primes

Fast implementation of the Sieve of Erathosthenes
https://github.com/ppetr/zillion-primes

Last synced: 8 months ago
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Fast implementation of the Sieve of Erathosthenes

Host: GitHub
URL: https://github.com/ppetr/zillion-primes
Owner: ppetr
License: apache-2.0
Created: 2024-03-08T21:30:14.000Z (over 2 years ago)
Default Branch: main
Last Pushed: 2024-03-30T12:50:39.000Z (about 2 years ago)
Last Synced: 2025-01-31T08:44:15.435Z (over 1 year ago)
Language: C++
Size: 16.6 KB
Stars: 0
Watchers: 2
Forks: 0
Open Issues: 0
Metadata Files:
- Readme: README.md
- Contributing: docs/contributing.md
- License: LICENSE
- Code of conduct: docs/code-of-conduct.md

README

# Zillion primes

*Disclaimer:* This is not an officially supported Google product.

This program uses the [Sieve of
Eratosthenes](https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes) to generate
primes up to a given bound.

On a standard low-end Intel Core i5 it produces ~7.9M primes per second.

It uses approximately _0.024√n_ bytes of RAM to compute primes up to _n._

## Output

The program emits primes to _stdout_ encoded as 64-bit binary [little-endian]
numbers.

This format is easily readable by programs, and can be even [`mmap`]-ed as an
`int64_t[]` array. Also allows to quickly read an N-th prime.

[`mmap`]: https://en.wikipedia.org/wiki/Mmap
[little-endian]: https://en.wikipedia.org/w/index.php?title=Endianness&oldid=1212636685#Numbers

## Compilation

```shell
$ clang++ -O3 sieve.cc -o sieve
```

`g++` works just as well, it just produces slightly slower (~15%) binary.

## Testing

The first 50.000.000 primes should satisfy the following hash:

```sh
$ ./sieve 982451653 | sha256sum
17d28fa909939b450dbd6b8923a1001c61bdc8cedb5e44a07f9f90b4d36ab279 -
```