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/* parallel computation of pi with monte carlo method */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/ipc.h>
#include <sys/shm.h>
int rdtsc()
{
__asm__ __volatile__("rdtsc");
}
double* Parallel( double* smem, pid_t* pid, int nbt, long int niter, int statut, int options, int nb_current )
{
double x,y,z;
long int i;
int j;
srand(rdtsc());
if (nbt==1)
{ smem[nb_current]=0;
for (i=0; i<(niter/nbt); i++)
{ x = (double) rand() / RAND_MAX;
y = (double) rand() / RAND_MAX;
z = x*x + y*y;
if (z <= 1.0)
{smem[nb_current]++;}}
return smem;
}
else if (nb_current==nbt) return smem;
else { pid[nb_current]=fork();
if (pid[nb_current]<0) {exit(4);}
else if (pid[nb_current]==0)
{ smem=Parallel(smem,pid,nbt,niter,statut,options,nb_current+2);
// child process
// compute the niter/nbt part of niter hits
smem[nb_current] = 0;
for (i=0; i<(niter/nbt); i++)
{ x = (double) rand() / RAND_MAX;
y = (double) rand() / RAND_MAX;
z = x*x + y*y;
if (z <= 1.0) {smem[nb_current]++; }
}
printf("------smem in child-----nb_current=%d ---\n",nb_current);
for(j=0;j<nbt;j++)
{printf("smem[%d]=%f\n",j,smem[j]);}
exit(0);
}
else
{ // parent process
// compute the niter/nbt part of niter hits
smem[nb_current+1] = 0;
for (i=0; i<(niter/nbt); i++)
{ x = (double) rand() / RAND_MAX;
y = (double) rand() / RAND_MAX;
z = x*x + y*y;
if (z <= 1.0) {smem[nb_current+1]++; }
}
waitpid(pid[nb_current],&statut,options);
printf("------smem in parent-----nb_current+1=%d ---\n",nb_current+1);
for(j=0;j<nbt;j++)
{printf("smem[%d]=%f\n",j,smem[j]);}
return smem;
}
}
}
int main (int argc, char** argv)
{ long int niter; // total number of hits
long int fd;long int i;
int shm_id;
int nb_process; // number of threads
int nb_current=0; // current index in Parallel recursive function
double x,y,z;
double pi=0;
// struct sharedMem* smem;
double* smem;
struct timeval chrono1, chrono2;
int micro, second; pid_t *pid;
int pseudo_pid;
int statut;
int options = 0;
// parse the argument
if (argc != 3)
{ printf ("Please, specify number of threads and iterations \n");
exit (1); }
nb_process = atoi(argv[1]);
niter = atol(argv[2]);
// create the shared memory
fd = open ("/tmp/myregion", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
if (fd == -1) exit(2);
if (ftruncate (fd, nb_process*sizeof (double)) == -1) exit(3);
smem = mmap (NULL, nb_process*sizeof (double),
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (smem == MAP_FAILED) exit(1);
// initialize pid
pid=(pid_t*)malloc(nb_process*sizeof(pid_t));
// initialize time process
gettimeofday(&chrono1, NULL);
// monte carlo's method in parallel
smem=Parallel(smem,pid,nb_process,niter,statut,options,nb_current);
gettimeofday(&chrono2, NULL);
close(fd);
// compute ellapsed time
micro = chrono2.tv_usec - chrono1.tv_usec;
if (micro < 0)
{ micro += 1000000;
second = chrono2.tv_sec - chrono1.tv_sec - 1; }
else
second = chrono2.tv_sec - chrono1.tv_sec;
//printf("-------------------------\n");
for(i=0;i<nb_process;i++)
{//printf("smem[%d]=%f\n",i,smem[i]);
pi = pi+ smem[i];}
pi= pi/niter;
pi *= 4;
// Output
printf("# of trials= %ld , estimate of pi is %1.8f \n",niter,pi);
printf("%d second %d micro ellapsed\n", second, micro);
/* Don't forget to free the mmapped memory
*/
if (munmap(smem, nb_process*sizeof (double)) == -1) {
printf("Error un-mmapping the file\n");
/* Decide here whether to close(fd) and exit() or not. Depends... */
}
/* Un-mmaping doesn't close the file, so we still need to do that.
*/
close(fd);
return 0;
} |
