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168 | #include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
typedef struct
{
size_t team_count;
sem_t* batons;
pthread_barrier_t start_barrier;
useconds_t stage1_duration;
useconds_t stage2_duration;
size_t position;
pthread_mutex_t position_mutex;
} shared_data_t;
typedef struct
{
size_t my_team_number;
shared_data_t* shared_data;
} private_data_t;
int analyze_arguments(int argc, char* argv[], shared_data_t* shared_data);
int create_threads(shared_data_t* shared_data);
void* start_race(void* data);
void* finish_race(void* data);
int main(int argc, char* argv[])
{
shared_data_t* shared_data = (shared_data_t*) calloc(1, sizeof(shared_data_t));
if ( shared_data == NULL )
return (void)fprintf(stderr, "error: could not allocate shared memory\n"), 1;
int error = analyze_arguments(argc, argv, shared_data);
if ( error == 0 )
{
shared_data->batons = (sem_t*) calloc(shared_data->team_count, sizeof(sem_t));
if ( shared_data->batons )
{
for ( size_t index = 0; index < shared_data->team_count; ++index )
sem_init(&shared_data->batons[index], 0 /*pshared*/, 0);
pthread_barrier_init(&shared_data->start_barrier, /*attr*/ NULL, shared_data->team_count);
shared_data->position = 0;
pthread_mutex_init(&shared_data->position_mutex, /*attr*/ NULL);
struct timespec start_time;
clock_gettime(CLOCK_MONOTONIC, &start_time);
error = create_threads(shared_data);
if ( error == 0 )
{
struct timespec finish_time;
clock_gettime(CLOCK_MONOTONIC, &finish_time);
double elapsed_seconds = finish_time.tv_sec - start_time.tv_sec
+ 1e-9 * (finish_time.tv_nsec - start_time.tv_nsec);
printf("Simulation time %.9lfs\n", elapsed_seconds);
}
pthread_mutex_destroy(&shared_data->position_mutex);
pthread_barrier_destroy(&shared_data->start_barrier);
free(shared_data->batons);
}
else
{
fprintf(stderr, "error: could not allocate memory for %zu batons\n", shared_data->team_count);
error = 2;
}
}
free(shared_data);
return error;
}
int analyze_arguments(int argc, char* argv[], shared_data_t* shared_data)
{
if ( argc != 4 )
{
fprintf(stderr, "usage: relay_race teams stage1_duration stage2_duration\n");
return 1;
}
if ( sscanf(argv[1], "%zu", &shared_data->team_count) != 1 || shared_data->team_count == 0 )
return (void)fprintf(stderr, "invalid team count: %s\n", argv[1]), 1;
if ( sscanf(argv[2], "%u", &shared_data->stage1_duration) != 1 )
return (void)fprintf(stderr, "invalid stage 1 duration: %s\n", argv[2]), 2;
if ( sscanf(argv[3], "%u", &shared_data->stage2_duration) != 1 )
return (void)fprintf(stderr, "invalid stage 2 duration: %s\n", argv[3]), 3;
return EXIT_SUCCESS;
}
int create_threads(shared_data_t* shared_data)
{
size_t thread_count = 2 * shared_data->team_count;
pthread_t* threads = (pthread_t*) malloc(thread_count * sizeof(pthread_t));
if ( threads == NULL )
return (void)fprintf(stderr, "error: could not allocate memory for %zu threads\n", thread_count), 2;
private_data_t* private_data = (private_data_t*) calloc(thread_count, sizeof(private_data_t));
if ( private_data == NULL )
return (void)fprintf(stderr, "error: could not allocate private memory for %zu threads\n", thread_count), 3;
#if INVERTED_TEAM_ORDER
for ( size_t index = shared_data->team_count - 1; index < shared_data->team_count; --index )
#else
for ( size_t index = 0; index < shared_data->team_count; ++index )
#endif
{
private_data[index].my_team_number = index;
private_data[index].shared_data = shared_data;
pthread_create(&threads[index], NULL, start_race, &private_data[index]);
}
#if INVERTED_TEAM_ORDER
for ( size_t index = thread_count - 1; index >= shared_data->team_count; --index )
#else
for ( size_t index = shared_data->team_count; index < thread_count; ++index )
#endif
{
private_data[index].my_team_number = index - shared_data->team_count;
private_data[index].shared_data = shared_data;
pthread_create(&threads[index], NULL, finish_race, &private_data[index]);
}
for ( size_t index = 0; index < thread_count; ++index )
pthread_join(threads[index], NULL);
free(private_data);
free(threads);
return 0;
}
void* start_race(void* data)
{
private_data_t* private_data = (private_data_t*)data;
shared_data_t* shared_data = private_data->shared_data;
pthread_barrier_wait(&shared_data->start_barrier);
usleep( 1000 * shared_data->stage1_duration );
sem_post(&shared_data->batons[private_data->my_team_number]);
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;
sem_wait(&shared_data->batons[private_data->my_team_number]);
usleep( 1000 * shared_data->stage2_duration );
pthread_mutex_lock(&shared_data->position_mutex);
if ( ++shared_data->position <= 3 )
printf("Place %zu: team %zu\n", shared_data->position, private_data->my_team_number + 1);
pthread_mutex_unlock(&shared_data->position_mutex);
return NULL;
}
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