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/*
** gcc -Wall -Wextra -pedantic -pedantic-errors
** -std=gnu99 -lpthread -lgmp -lprimesieve
*/
 
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
#include <gmp.h>
#include <primesieve.h>
 
#define FILENAME "/dev/stdout"
#define SIZE 1000000000000
#define NTHREADS 4
#define PRECISION 512
#define LENGTH 1000
#define RESOLUTION 1000
 
mpf_t Sum;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_barrier_t barrier;
 
unsigned long int primes[NTHREADS] = { 0 };
 
void *job (void *arg)
{
    unsigned long int index, n, p, size, end;
    primesieve_iterator it;
    time_t t;
    struct tm *time_p;
    FILE *f;
    char buf[BUFSIZ];
    mpf_t N, Localsum;
 
    pthread_mutex_lock(&mutex);
 
    index = *((unsigned long int*)arg);
    size = SIZE/NTHREADS;
    n = size*index;
 
    if (index == NTHREADS - 1)
    {
        end = SIZE - 1;
    }
    else
    {
        end = n + size - 1;
    }
 
    mpf_set_default_prec((mp_bitcnt_t)PRECISION);
    mpf_inits(N, Localsum, NULL);
 
    f = fopen(FILENAME, "w");
    setvbuf(f, buf, _IOLBF, BUFSIZ);
 
    fprintf(f, "%ld: from %ld to %ld\n", index, n + 1, end + 1);
 
    time(&t);
    time_p = localtime(&t);
    fprintf(f, "[%04d-%02d-%02d %02d:%02d:%02d] %ld: skipping...\n",
        time_p->tm_year + 1900, time_p->tm_mon + 1, time_p->tm_mday,
        time_p->tm_hour, time_p->tm_min, time_p->tm_sec, index);
 
    if (primes[index])
    {
        primesieve_init(&it);
        p = primes[index];
        primesieve_skipto(&it, p - 1, p + size);
    }
    else
    {
        primesieve_init(&it);
        p = primesieve_nth_prime(n + 1, 0);
        printf("%ld\n", p);
        primesieve_skipto(&it, p - 1, p + size);
    }
 
    pthread_mutex_unlock(&mutex);
 
    pthread_barrier_wait(&barrier);
 
    time(&t);
    time_p = localtime(&t);
    fprintf(f, "[%04d-%02d-%02d %02d:%02d:%02d] %ld: calculating...\n",
        time_p->tm_year + 1900, time_p->tm_mon + 1, time_p->tm_mday,
        time_p->tm_hour, time_p->tm_min, time_p->tm_sec, index);
 
    while (n <= end)
    {
        mpf_set_ui(N, ++n);
        mpf_div_ui(N, N, (unsigned long int)primesieve_next_prime(&it));
        mpf_sub(Localsum, Localsum, N);
 
        time(&t);
        time_p = localtime(&t);
        fprintf(f, "[%04d-%02d-%02d %02d:%02d:%02d] %ld: %ld\n",
            time_p->tm_year + 1900, time_p->tm_mon + 1,
            time_p->tm_mday, time_p->tm_hour,
            time_p->tm_min, time_p->tm_sec, index, n);
 
        mpf_set_ui(N, ++n);
        mpf_div_ui(N, N, (unsigned long int)primesieve_next_prime(&it));
        mpf_add(Localsum, Localsum, N);
 
        time(&t);
        time_p = localtime(&t);
        fprintf(f, "[%04d-%02d-%02d %02d:%02d:%02d] %ld: %ld\n",
            time_p->tm_year + 1900, time_p->tm_mon + 1,
            time_p->tm_mday, time_p->tm_hour,
            time_p->tm_min, time_p->tm_sec, index, n);
 
        for (unsigned long int i = 0; i < size/RESOLUTION - 1; i++)
        {
            mpf_set_ui(N, ++n);
            mpf_div_ui(N, N,
                (unsigned long int)primesieve_next_prime(&it));
            mpf_sub(Localsum, Localsum, N);
 
            mpf_set_ui(N, ++n);
            mpf_div_ui(N, N,
                (unsigned long int)primesieve_next_prime(&it));
            mpf_add(Localsum, Localsum, N);
        }
    }
 
    primesieve_free_iterator(&it);
 
    time(&t);
    time_p = localtime(&t);
    fprintf(f, "[%04d-%02d-%02d %02d:%02d:%02d] %ld: done! partial result: ",
        time_p->tm_year + 1900, time_p->tm_mon + 1, time_p->tm_mday,
        time_p->tm_hour, time_p->tm_min, time_p->tm_sec, index);
    mpf_out_str(f, 10, (size_t)LENGTH, Localsum);
    fprintf(f, "\n");
 
    fclose(f);
 
    mpf_add(Sum, Sum, Localsum);
 
    mpf_clears(N, Localsum, NULL);
 
    return NULL;
}
 
int main (int argc, char *argv[])
{
    pthread_t threads[NTHREADS];
    unsigned long int args[NTHREADS];
    int i;
    FILE *f;
    char buf[BUFSIZ];
    time_t t;
    struct tm *time_p;
 
    mpf_set_default_prec((mp_bitcnt_t)PRECISION);
    mpf_init(Sum);
 
    pthread_barrier_init(&barrier, NULL, NTHREADS);
 
    f = fopen(FILENAME, "w");
    setvbuf(f, buf, _IOLBF, BUFSIZ);
 
    time(&t);
    time_p = localtime(&t);
 
    fprintf(f, "[%04d-%02d-%02d %02d:%02d:%02d] M: started\n",
        time_p->tm_year + 1900, time_p->tm_mon + 1, time_p->tm_mday,
        time_p->tm_hour, time_p->tm_min, time_p->tm_sec);
 
    fprintf(f, "precision: %d bits\n\n", (int)mpf_get_prec(Sum));
 
    for (i = 0; i < argc - 1; i++)
    {
        primes[i] = strtoul(argv[i + 1], NULL, 10);
        printf("%ld\n", primes[i]);
    }
 
    for (i = 0; i < NTHREADS; i++)
    {
        args[i] = i;
        pthread_create(&threads[i], NULL, job, &args[i]);
    }
 
    for (i = 0; i < NTHREADS; i++)
    {
        pthread_join(threads[i], NULL);
    }
 
    fprintf(f, "\nM: total result: ");
    mpf_out_str(f, 10, (size_t)LENGTH, Sum);
    fprintf(f, "\n");
 
    fclose(f);
 
    mpf_clear(Sum);
 
    return EXIT_SUCCESS;
}