primesieve
7.5
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primesieve_iterator allows to easily iterate over primes both forwards and backwards. Generating the first prime has a complexity of O(r log log r) operations with r = n^0.5, after that any additional prime is generated in amortized O(log n log log n) operations. The memory usage is about PrimePi(n^0.5) * 8 bytes. More...
#include <stdint.h>
#include <stddef.h>
Classes | |
struct | primesieve_iterator |
C prime iterator, please refer to iterator.h for more information. More... | |
Functions | |
void | primesieve_init (primesieve_iterator *it) |
Initialize the primesieve iterator before first using it. | |
void | primesieve_free_iterator (primesieve_iterator *it) |
Free all memory. | |
void | primesieve_skipto (primesieve_iterator *it, uint64_t start, uint64_t stop_hint) |
Reset the primesieve iterator to start. More... | |
static uint64_t | primesieve_next_prime (primesieve_iterator *it) |
Get the next prime. More... | |
static uint64_t | primesieve_prev_prime (primesieve_iterator *it) |
Get the previous prime. More... | |
primesieve_iterator allows to easily iterate over primes both forwards and backwards. Generating the first prime has a complexity of O(r log log r) operations with r = n^0.5, after that any additional prime is generated in amortized O(log n log log n) operations. The memory usage is about PrimePi(n^0.5) * 8 bytes.
The primesieve_iterator.c example shows how to use primesieve_iterator. If any error occurs primesieve_next_prime() and primesieve_prev_prime() return PRIMESIEVE_ERROR. Furthermore primesieve_iterator.is_error is initialized to 0 and set to 1 if any error occurs.
Copyright (C) 2019 Kim Walisch, kim.w alis ch@gm ail. com
This file is distributed under the BSD License. See the COPYING file in the top level directory.
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inlinestatic |
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inlinestatic |
Get the previous prime.
primesieve_prev_prime(n) returns 0 for n <= 2. Note that primesieve_next_prime() runs up to 2x faster than primesieve_prev_prime(). Hence if the same algorithm can be written using either primesieve_prev_prime() or primesieve_next_prime() it is preferable to use primesieve_next_prime().
void primesieve_skipto | ( | primesieve_iterator * | it, |
uint64_t | start, | ||
uint64_t | stop_hint | ||
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Reset the primesieve iterator to start.
start | Generate primes > start (or < start). |
stop_hint | Stop number optimization hint. E.g. if you want to generate the primes below 1000 use stop_hint = 1000, if you don't know use primesieve_get_max_stop(). |