# primesieve - Man Page

generate prime numbers

## Synopsis

`primesieve [START] STOP [OPTION]...`

## Description

Generate the prime numbers and/or prime k-tuplets inside [START, STOP] (< 2^64) using the segmented sieve of Eratosthenes. primesieve includes a number of extensions to the sieve of Eratosthenes which significantly improve performance: multiples of small primes are pre-sieved, it uses wheel factorization to skip multiples with small prime factors and it uses the bucket sieve algorithm which improves cache efficiency when sieving > 2^32. primesieve is also multi-threaded, it uses all available CPU cores by default for counting primes and for finding the nth prime.

The segmented sieve of Eratosthenes has a runtime complexity of O(n log log n) operations and it uses O(n^(1/2)) bits of memory. More specifically primesieve uses 8 bytes per sieving prime, hence its memory usage can be approximated by PrimePi(n^(1/2)) * 8 bytes (per thread).

## Options

-c[NUM+], --count[=NUM+]

Count primes and/or prime k-tuplets, 1 <= NUM <= 6. Count primes: -c or --count, count twin primes: -c2 or --count=2, count prime triplets: -c3 or --count=3, ... You can also count primes and prime k-tuplets at the same time, e.g. -c123 counts primes, twin primes and prime triplets.

--cpu-info

Print CPU information: CPU name, frequency, number of cores, cache sizes, ...

-d,  --dist=DIST

Sieve the interval [START, START + DIST].

-h,  --help

-n,  --nth-prime

Find the nth prime, e.g. 100 -n finds the 100th prime. If 2 numbers N START are provided finds the nth prime > START, e.g. 2 100 -n finds the 2nd prime > 100.

--no-status

Turn off the progressing status.

-p[NUM], --print[=NUM]

Print primes or prime k-tuplets, 1 <= NUM <= 6. Print primes: -p, print twin primes: -p2, print prime triplets: -p3, ...

-q,  --quiet

Quiet mode, prints less output.

-s,  --size=SIZE

Set the size of the sieve array in KiB, 16 <= SIZE <= 8192. By default primesieve uses a sieve size that matches your CPU’s L1 cache size (per core) or is slightly smaller than your CPU’s L2 cache size. This setting is crucial for performance, on exotic CPUs primesieve sometimes fails to determine the CPU’s cache sizes which usually causes a big slowdown. In this case you can get a significant speedup by manually setting the sieve size to your CPU’s L1 or L2 cache size (per core).

--test

Run various sieving tests.

Set the number of threads, 1 <= NUM <= CPU cores. By default primesieve uses all available CPU cores for counting primes and for finding the nth prime.

--time

Print the time elapsed in seconds.

-v,  --version

## Examples

primesieve 1000

Count the primes <= 1000.

primesieve 1e6 --print

Print the primes <= 10^6.

primesieve 1e6 --print > primes.txt

Store the primes <= 10^6 in a text file.

primesieve 2^32 --print=2

Print the twin primes <= 2^32.

Count the primes inside [10^16, 10^16 + 10^10] using a single thread.

## Homepage

https://github.com/kimwalisch/primesieve

## Author

Kim Walisch <kim.walisch@gmail.com>

05/13/2023