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findprimes.cpp
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findprimes.cpp
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/*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
* Copyright (C) 2019 Stefan Teleman.
*/
#include <iostream>
#include <vector>
#include <set>
#include <cstdint>
#include <cmath>
#include <ctime>
#include <climits>
#include <cstring>
#include <cerrno>
#include <unistd.h>
#include <pthread.h>
#include <sys/select.h>
static uint64_t range_start = 1UL;
static uint64_t range_end = 0UL;
static uint64_t prime_index = 0UL;
static uint32_t nthreads = 4U;
static std::set<uint64_t> prime_storage;
static bool print_header = false;
static bool print_timestamp = false;
static struct timespec ts_begin = { 0, 0 };
static struct timespec ts_end = { 0, 0 };
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static std::vector<pthread_attr_t> tattr;
struct prime_range {
prime_range() : start(0UL), end(0UL), tid(0U) { }
prime_range(const prime_range& rhs)
: start(rhs.start), end(rhs.end), tid(rhs.tid) { }
~prime_range() = default;
prime_range& operator=(const prime_range& rhs) {
if (this != &rhs) {
start = rhs.start;
end = rhs.end;
tid = rhs.tid;
}
return *this;
}
uint64_t start;
uint64_t end;
uint32_t tid;
};
static pthread_t monitor_thread;
static std::vector<pthread_t> threads;
static std::vector<prime_range> ranges;
static uint32_t thread_count = 0U;
static void print_help(void)
{
std::cerr << "Usage: findprimes [-s <range-start> (default 1)]" << std::endl;
std::cerr << " [ -e <range-end> default ULONG_MAX | ULLONG_MAX)]"
<< std::endl;
std::cerr << " [ -b <number-of-bits> (default 64)]" << std::endl;
std::cerr << " [ -T <number-of-threads> (default 4)]" << std::endl;
std::cerr << " [ -f <output-file> (default stdout)]" << std::endl;
std::cerr << " [ -p <print header at the top>]" << std::endl;
std::cerr << " [ -t <print prime discovery time>]" << std::endl;
}
static void timestamp(struct timespec* ts)
{
errno = 0;
if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, ts) != 0) {
(void) fprintf(stderr, "Could not get the timestamp: %s\n",
std::strerror(errno));
}
}
static void print_time(const char* filename)
{
FILE* fp = NULL;
if (filename) {
errno = 0;
if ((fp = fopen(filename, "a")) == NULL) {
std::cerr << "Unable to open file '" << filename << "' for writing: "
<< std::strerror(errno) << std::endl;
return;
}
} else
fp = stdout;
uint64_t sec = (uint64_t) ts_end.tv_sec - ts_begin.tv_sec;
uint64_t nns = (uint64_t) ts_end.tv_nsec - ts_begin.tv_nsec;
if (nns >= 1000000000) {
sec += nns / 1000000000;
nns = nns % 1000000000;
}
(void) std::fprintf(fp, "-----\n");
(void) std::fprintf(fp, "Discovered %lu prime numbers in %lu.%.16lu seconds.\n",
prime_index, sec, nns);
(void) std::fflush(fp);
if (filename)
(void) fclose(fp);
}
bool is_prime(uint64_t x)
{
if (x == 2 || !(x & 0x1) || (x == 0))
return false;
uint64_t s = (uint64_t) std::ceil(std::sqrt(x));
for (uint64_t i = 3UL; i <= s; i += 2UL) {
if ((x % i) == 0) {
return false;
}
}
return true;
}
static int check_bits(unsigned bits)
{
if ((bits == 32) && (range_end > UINT_MAX)) {
(void) fprintf(stderr, "end-range exceeds 32-bit UINT_MAX.\n");
return -1;
}
return 0;
}
void add_prime(uint64_t x)
{
(void) pthread_mutex_lock(&mutex);
prime_storage.insert(x);
prime_index = prime_storage.size();
(void) pthread_mutex_unlock(&mutex);
}
static int print_primes(const char* filename)
{
FILE* fp = NULL;
if (filename) {
errno = 0;
if ((fp = std::fopen(filename, "w+")) == NULL) {
(void) std::fprintf(stderr, "Unable to open file '%s' for writing: %s\n",
filename, strerror(errno));
return -1;
}
} else
fp = stdout;
if (print_header)
(void) std::fprintf(fp, "List of prime numbers in the range %lu - %lu:\n\n",
range_start, range_end);
for (std::set<uint64_t>::const_iterator pi = prime_storage.begin();
pi != prime_storage.end(); ++pi)
(void) std::fprintf(fp, "%lu\n", (*pi));
(void) fflush(fp);
if (filename && fp != stdout)
(void) fclose(fp);
return 0;
}
extern "C" {
void* prime_thread_start(void* arg) {
prime_range* pr = (prime_range*) arg;
uint32_t pc = 0U;
for (uint64_t p = pr->start; p <= pr->end; p += 2) {
if (is_prime(p)) {
add_prime(p);
++pc;
}
}
(void) std::fprintf(stderr, "thread %u [%lu -> %lu] is done [%u].\n",
pr->tid, pr->start, pr->end, pc);
(void) std::fflush(stderr);
pthread_mutex_lock(&mutex);
thread_count += 1U;
pthread_mutex_unlock(&mutex);
return NULL;
}
void* monitor_thread_start(void*) {
struct timeval ttv = { 0, 100 };
uint32_t tc = 0U;
pthread_mutex_lock(&mutex);
tc = thread_count;
pthread_mutex_unlock(&mutex);
while (tc < nthreads) {
select(0, NULL, NULL, NULL, &ttv);
ttv.tv_sec = 0;
ttv.tv_usec = 1000;
pthread_mutex_lock(&mutex);
tc = thread_count;
pthread_mutex_unlock(&mutex);
}
ttv.tv_sec = 0;
ttv.tv_usec = 1000;
select(0, NULL, NULL, NULL, &ttv);
(void) std::fprintf(stderr, "monitor thread is done.\n");
return NULL;
}
}
static void find_primes(void)
{
uint64_t eff_range_start = range_start;
if (eff_range_start == 1UL) {
add_prime(1UL);
add_prime(2UL);
eff_range_start = 3UL;
} else if (eff_range_start == 2UL) {
add_prime(2UL);
eff_range_start = 3UL;
}
if ((eff_range_start % 2) == 0)
eff_range_start += 1;
uint64_t segment = std::ceil((range_end - eff_range_start) / nthreads);
ranges.resize(nthreads);
ranges[0].start = eff_range_start;
ranges[0].end = ranges[0].start + segment;
if (!(ranges[0].end & 0x1))
ranges[0].end += 1UL;
uint32_t i;
for (i = 1; i < nthreads - 1; ++i) {
ranges[i].start = ranges[i - 1].end;
ranges[i].end = ranges[i].start + segment;
if (!(ranges[i].end & 0x1))
ranges[i].end += 1UL;
}
ranges[nthreads - 1].start = ranges[i - 1].end;
ranges[nthreads - 1].end = range_end;
for (i = 0; i < nthreads; ++i) {
(void) std::fprintf(stderr, "range[%u]: %lu --> %lu\n",
i, ranges[i].start, ranges[i].end);
}
tattr.resize(nthreads);
threads.resize(nthreads);
for (i = 0; i < nthreads; ++i) {
(void) pthread_attr_init(&tattr[i]);
(void) pthread_attr_setdetachstate(&tattr[i], PTHREAD_CREATE_DETACHED);
}
struct timeval mtv = { 0, 1000 };
(void) pthread_create(&monitor_thread, NULL, monitor_thread_start, NULL);
select(0, NULL, NULL, NULL, &mtv);
timestamp(&ts_begin);
for (i = 0; i < nthreads; ++i) {
std::cerr << "starting thread " << i << " ..." << std::endl;
ranges[i].tid = i;
pthread_create(&threads[i], &tattr[i], prime_thread_start, &ranges[i]);
}
(void) pthread_join(monitor_thread, NULL);
timestamp(&ts_end);
}
int main(int argc, char* argv[])
{
int opt;
unsigned bits = 64;
bool ph = false;
const char* filename = NULL;
while ((opt = getopt(argc, argv, "hpts:e:b:f:T:")) != -1) {
switch (opt) {
case 'h':
ph = true;
break;
case 'b':
bits = (unsigned) strtoul(optarg, NULL, 10);
break;
case 's':
range_start = (uint64_t) strtoul(optarg, NULL, 10);
break;
case 'e':
range_end = (uint64_t) strtoul(optarg, NULL, 10);
break;
case 'f':
filename = optarg;
break;
case 'p':
print_header = true;
break;
case 't':
print_timestamp = true;
break;
case 'T':
nthreads = (uint32_t) strtoul(optarg, NULL, 10);
break;
default:
ph = true;
break;
}
}
if (ph) {
print_help();
return 1;
}
if (nthreads < 4) {
(void) std::fprintf(stderr, "At least 4 threads are required.\n");
return 1;
}
if (range_start == 0)
range_start = 1UL;
if (range_end == 0)
range_end = bits == 32 ? UINT_MAX : ULLONG_MAX;
if (check_bits(bits) != 0)
return 1;
find_primes();
if (print_primes(filename) != 0)
return 1;
if (print_timestamp) {
print_time(filename);
}
return 0;
}