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/*
To run this:
$ gcc pi.c -pthread -o pi
./pi
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/uio.h>
#include <assert.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/signal.h>
#include <sys/wait.h>
#define kPI 5e7
typedef struct {
int id;
pid_t pid;
pthread_t thread;
} threadData;
struct timeval t0;
void timer_start () {
gettimeofday(&t0, NULL);
}
double timer_end () {
struct timeval t1;
gettimeofday(&t1, NULL);
return (double) (((double)t1.tv_sec)+ ((double)t1.tv_usec*1.0e-6))- (((double)t0.tv_sec)+ ((double)t0.tv_usec*1.0e-6));
}
double pi (double n) {
double pi= 0;
double num= 4;
double den= 1;
int plus= 1;
while (den < n) {
if (plus) {
pi+= num/den;
plus= 0;
}
else {
pi-= num/den;
plus= 1;
}
den+= 2;
}
return pi;
}
void* thread_proc (void* arg) {
fprintf(stdout, "%.16f -> TID[%d]\n", pi(kPI), ((threadData*) arg)->id);
return NULL;
}
int main (int argc, char *argv[]) {
double tThreads= 0, tProcs= 0;
int numThreads= (argc > 1) ? atoi(argv[1]): 33;
threadData* threads= (threadData*) malloc(numThreads* sizeof(threadData));
// USING PROCESSES
fprintf(stdout, "\n**** Using %d processes\n", numThreads);
timer_start();
{
pid_t pid;
int i= numThreads;
while (i--) {
threads[i].id= numThreads- i;
threads[i].pid= pid= fork();
if (!pid) {
//child
fprintf(stdout, "%.16f -> PID[%d]\n", pi(kPI), threads[i].id);
exit(0);
}
else if (pid < 0) {
fprintf(stdout, "**** Error: fork(): -1\n");
while (++i < numThreads) {
kill(threads[i].pid, SIGKILL);
}
exit(-1);
}
}
i= numThreads;
while (i--) {
waitpid(WAIT_ANY, NULL, 0);
}
}
tProcs= timer_end();
// USING THREADS
fprintf(stdout, "\n**** Using %d threads\n", numThreads);
timer_start();
{
int i= numThreads;
while (i--) {
threads[i].id= numThreads- i;
pthread_create(&threads[i].thread, NULL, thread_proc, &threads[i]);
}
i= numThreads;
while (i--) {
pthread_join(threads[i].thread, NULL);
}
}
tThreads= timer_end();
fprintf(stdout, "\n*** Procesos:\n");
fprintf(stdout, "Tiempo total (ms) -> %.0f\n", tProcs*1e3);
fprintf(stdout, "Procesos por segundo -> %.1f\n", (double)(numThreads/tProcs));
fprintf(stdout, "Total de procesos ejecutadas -> %d\n", numThreads);
fprintf(stdout, "\n*** Threads:\n");
fprintf(stdout, "Tiempo total (ms) -> %.0f\n", tThreads*1e3);
fprintf(stdout, "Threads por segundo -> %.1f\n", (double)(numThreads/tThreads));
fprintf(stdout, "Total de threads ejecutadas -> %d\n", numThreads);
fprintf(stdout, "\nRatio t_Threads/t_Procesos -> %.4f\n", (double)(tThreads/tProcs));
free(threads);
}
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