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threadpmult.c
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threadpmult.c
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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
/* arrays to be populated by each thread */
unsigned long long *best_numbers;
unsigned int *best_levels;
/* argument structure for explore_range function */
typedef struct {
unsigned long long min;
unsigned long long max;
unsigned int thread;
} explore_range_args;
explore_range_args *init_explore_range_args(unsigned long long int min,
unsigned long long int max,
unsigned long int thread,
unsigned long int num_threads)
{
/* returns pointer to explore_range_args struct */
explore_range_args *ret_val = malloc(sizeof(explore_range_args));
/* dividing the range into equal parts for each thread */
unsigned long long int range_min = min + ((max - min) / num_threads) * thread;
unsigned long long int range_max = ((thread +1) == num_threads) ? max:
min + ((max - min) / num_threads) * (thread + 1);
ret_val->min = range_min;
ret_val->max = range_max;
ret_val->thread = thread;
return ret_val;
}
unsigned long long multiply_digits(unsigned long long n)
{
/*
* return the product of all digits in n
*/
unsigned long long product = 1;
while (n > 0) {
product *= (n % 10);
n /= 10;
}
return product;
}
unsigned int multiplicative_persistence(unsigned long long n)
{
/*
* return the number of rounds n can pass
*/
unsigned int levels = 0;
while (n > 9) {
levels++;
n = multiply_digits(n);
}
return levels;
}
void *explore_range(void *thread_args)
{
/* runs in pthread and populates best_numbers and best_levels arrays */
unsigned long long int current;
unsigned int current_levels;
/* casting arguments */
explore_range_args *args = (explore_range_args *) thread_args;
printf("Min: %llu, Max: %llu, Thread: %u\n", args->min, args->max,
args->thread);
//printf("DEBUG: %llu, %llu\n", best_numbers[args->thread], args->min);
/* finding number with highest multiplicative persistence within given range */
for (current = args->min; current <= args->max; current++) {
current_levels = multiplicative_persistence(current);
/* if number found with more levels or number hasn't been set */
if ((current_levels > best_levels[args->thread]) || (best_numbers[args->thread] < args->min)) {
best_numbers[args->thread] = current;
best_levels[args->thread] = current_levels;
}
}
free(args);
return NULL;
}
int main(int argc, char **argv)
{
unsigned long long int max;
unsigned long long int min;
unsigned long long int current;
unsigned long int num_threads;
unsigned long int i;
explore_range_args *args;
pthread_t *threads;
int ret_val;
unsigned long long int best = 0;
unsigned int best_level = 0;
/*
* checking args
*/
if ((argc != 2) && (argc != 4)) {
fprintf(stderr, "usage: %s min max threads OR %s number\n",
argv[0], argv[0]);
return EXIT_FAILURE;
}
if (argc == 2) {
current = strtoull(argv[1], NULL, 10);
printf("Number: %llu\nLevels: %u\n", current,
multiplicative_persistence(current));
return EXIT_SUCCESS;
}
if (argc == 4) {
/* parsing arguments */
min = strtoull(argv[1], NULL, 10);
max = strtoull(argv[2], NULL, 10);
num_threads = strtoul(argv[3], NULL, 10);
/* initializing arrays for threads */
best_numbers =
calloc(num_threads, sizeof(unsigned long long int));
best_levels = calloc(num_threads, sizeof(unsigned int));
threads = malloc(num_threads * sizeof(pthread_t));
/* creating threads */
for (i = 0; i < num_threads; i++) {
args = init_explore_range_args(min, max, i, num_threads);
if ((ret_val =
pthread_create(threads + i, NULL, explore_range,
args))) {
fprintf(stderr, "Thread creation failed!\n");
exit(EXIT_FAILURE);
}
}
/* finding best result */
for (i = 0; i < num_threads; i++) {
pthread_join(threads[i], NULL);
printf("Thread %lu complete!\n", i);
if ((best_levels[i] > best_level) || (best < min))
{
best = best_numbers[i];
best_level = best_levels[i];
}
}
/* freeing memory */
free(best_numbers);
free(best_levels);
free(threads);
}
printf("\n\nBest Number: %llu\nLevels: %u\n", best, best_level);
return EXIT_SUCCESS;
}