set CPU affinity of a particular pthread failure

Question

My speedup-example.cpp source code is shown below

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include "tern/user.h"

#define N 8
#define M 10000

int nwait = 0;
int nexit = 0;
volatile long long sum;
long loops = 6e3;
pthread_mutex_t mutex;
pthread_cond_t cond;
pthread_barrier_t bar;

void set_affinity(int core_id) {
  cpu_set_t cpuset;
  CPU_ZERO(&cpuset);
  CPU_SET(core_id, &cpuset);
  assert(pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpuset) ==0);
}

void* thread_func(void *arg) {
  set_affinity((int)(long)arg);
  for (int j = 0; j < M; j++) {
    pthread_mutex_lock(&mutex);
    nwait++;
    for (long i = 0; i < loops; i++) // This is the key of speedup for parrot: the mutex needs to be a little bit congested.
      sum += i;
    pthread_cond_wait(&cond, &mutex);
    pthread_mutex_unlock(&mutex);
    soba_wait(0);
    pthread_barrier_wait(&bar);
    for (long i = 0; i < loops; i++)
      sum += i*i*i*i*i*i;
    //fprintf(stderr, "compute thread %u %d\n", (unsigned)thread, sched_getcpu());
  }
}

int main(int argc, char *argv[]) {
  set_affinity(23);
  soba_init(0, N, 20);
  pthread_t th[N];
  int ret;
  pthread_cond_init(&cond, NULL);
  pthread_barrier_init(&bar, NULL, N);

  for(unsigned i=0; i<N; ++i) {
    ret  = pthread_create(&th[i], NULL, thread_func, (void*)i);
    assert(!ret && "pthread_create() failed!");
  }

  for (int j = 0; j < M; j++) {
    while (nwait < N) {
      sched_yield();
    }
    pthread_mutex_lock(&mutex);
    nwait = 0;
    //fprintf(stderr, "broadcast %u %d\n", (unsigned)pthread_self(), sched_getcpu());
    pthread_cond_broadcast(&cond);
    pthread_mutex_unlock(&mutex);
  }

  for(unsigned i=0; i<N; ++i)
    pthread_join(th[i], NULL);

  exit(0);
}

I already succeeded wrote the mk of speedup-example.cpp

gcc speedup-example.cpp -o speedup-example -O2 -g \-I$XTERN_ROOT/include -L$XTERN_ROOT/dync_hook -Wl,--rpath,$XTERN_ROOT/dync_hook -lxtern-annot \-lpthread 

But when I want to run it, problems occur. For example

$ time ./speedup-example

It informs me that

speedup-example.cpp:23: void set_affinity(int): Assertion `pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpuset) ==0' failed.

Can someone help me solve this problem? Many thanks.