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167 | // Copyright 2021 Jeisson Hidalgo <jeisson.hidalgo@ucr.ac.cr> CC-BY 4.0
#define _DEFAULT_SOURCE
#include <assert.h>
#include <inttypes.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
typedef struct shared_data {
size_t team_count;
useconds_t stage1_duration;
useconds_t stage2_duration;
size_t position;
} shared_data_t;
typedef struct private_data {
size_t thread_number; // rank
shared_data_t* shared_data;
} private_data_t;
int create_threads(shared_data_t* shared_data);
int analyze_arguments(int argc, char* argv[], shared_data_t* shared_data);
void* start_race(void* data);
void* finish_race(void* data);
int main(int argc, char* argv[]) {
int error = EXIT_SUCCESS;
shared_data_t* shared_data = (shared_data_t*)
calloc(1, sizeof(shared_data_t));
if (shared_data) {
error = analyze_arguments(argc, argv, shared_data);
if (error == EXIT_SUCCESS) {
shared_data->position = 0;
if (error == EXIT_SUCCESS) {
struct timespec start_time, finish_time;
clock_gettime(/*clk_id*/CLOCK_MONOTONIC, &start_time);
error = create_threads(shared_data);
clock_gettime(/*clk_id*/CLOCK_MONOTONIC, &finish_time);
double elapsed_time = finish_time.tv_sec - start_time.tv_sec +
(finish_time.tv_nsec - start_time.tv_nsec) * 1e-9;
printf("execution time: %.9lfs\n", elapsed_time);
} else {
fprintf(stderr, "error: could not init mutex\n");
error = 11;
}
}
free(shared_data);
} else {
fprintf(stderr, "error: could not allocated shared memory\n");
error = 12;
}
return error;
}
int analyze_arguments(int argc, char* argv[]
, shared_data_t* shared_data) {
if (argc == 4) {
if ( sscanf(argv[1], "%zu", &shared_data->team_count) != 1
|| shared_data->team_count == 0 ) {
fprintf(stderr, "invalid team count: %s\n", argv[1]);
return 11;
}
if ( sscanf(argv[2], "%u", &shared_data->stage1_duration) != 1 ) {
fprintf(stderr, "invalid stage 1 duration: %s\n", argv[2]);
return 12;
}
if ( sscanf(argv[3], "%u", &shared_data->stage2_duration) != 1 ) {
fprintf(stderr, "invalid stage 2 duration: %s\n", argv[3]);
return 13;
}
return EXIT_SUCCESS;
} else {
fprintf(stderr, "usage: relay_race teams stage1duration stage2duration\n");
return 10;
}
}
int create_threads(shared_data_t* shared_data) {
int error = EXIT_SUCCESS;
const size_t thread_count = 2 * shared_data->team_count;
pthread_t* threads = (pthread_t*) malloc(thread_count * sizeof(pthread_t));
private_data_t* private_data = (private_data_t*)
calloc(thread_count, sizeof(private_data_t));
if (threads && private_data) {
for (size_t index = 0; index < shared_data->team_count; ++index) {
private_data[index].thread_number = index;
private_data[index].shared_data = shared_data;
error = pthread_create(&threads[index], NULL, start_race
, &private_data[index]);
if (error) {
fprintf(stderr, "error: could not create thread %zu\n", index);
error = 21;
}
}
for (size_t index = shared_data->team_count; index < thread_count;
++index) {
private_data[index].thread_number = index;
private_data[index].shared_data = shared_data;
error = pthread_create(&threads[index], NULL, finish_race
, &private_data[index]);
if (error) {
fprintf(stderr, "error: could not create thread %zu\n", index);
error = 21;
}
}
for (size_t index = 0; index < thread_count; ++index) {
pthread_join(threads[index], NULL);
}
free(private_data);
free(threads);
} else {
fprintf(stderr, "error: could not allocate memory for %zu threads\n"
, shared_data->team_count);
error = 22;
}
return error;
}
void* start_race(void* data) {
private_data_t* private_data = (private_data_t*)data;
shared_data_t* shared_data = private_data->shared_data;
usleep(1000 * shared_data->stage1_duration);
return NULL;
}
void* finish_race(void* data) {
private_data_t* private_data = (private_data_t*)data;
shared_data_t* shared_data = private_data->shared_data;
const size_t team_number = private_data->thread_number
- shared_data->team_count;
assert(team_number < shared_data->team_count);
usleep(1000 * shared_data->stage2_duration);
const size_t our_position = ++shared_data->position;
printf("Place %zu: team %zu\n", our_position, team_number);
return NULL;
}
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