尝试使用pthreads，获得munmap错误？

Question

I am trying to do a numerical integration using simpsons rule, so I thought the best way to do this is in three threads, one for 2's one for 3's and then the end bounds.

But I am new to threads and am still learning some things. However, I don't really know whats wrong with this, I create the thread with its attributes and sent it off, then I free the attributes and try to join the threads as they become available, did I do this wrong? Is there a better way to do it?

Thank you for any help!

Code attached::

#include <stdio.h>
#include <math.h>
#include <pthread.h>
#include <unistd.h>
#include <time.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/wait.h>


#define PI 3.1415926535897932384626433832795028841971693993751058

float h_val, x_i, a_bound, b_bound, n_slices;
long double temp_vals[4];
int first, second = 0;

void * threes (void *t)
{
    long double a_n;
    long double seq_threes;
    long double x_i;
    long tid = (long)t;
    long double threes_sum = 0;
    for(int i = 1; i < n_slices; i++)
    {
        a_n = .25*((6*i)-(pow((-1),i))-3);
        x_i = a_n * (PI / n_slices);
        printf("Value of i :: %d  Value of x_i :: %Lf \n", i, x_i);
        seq_threes = 3*pow(((sin(PI*sin(x_i)))/(PI*sin(x_i))),2);
        threes_sum = threes_sum + seq_threes;
    }

    temp_vals[0] = threes_sum;
    pthread_exit((void*) t);
    return EXIT_SUCCESS;
}

void * twos (void *t)
{
    long double a_n;
    long double seq_twos;
    long double x_i;
    long double twos_sum = 0;
    long tid = (long)t;
    for(int i = 1; i < n_slices; i++)
    {
        a_n = 3*i;
        x_i = a_n * (PI / n_slices);
        printf("Value of i :: %d  Value of x_i :: %Lf \n", i, x_i);
        seq_twos = 2*pow(((sin(PI*sin(x_i)))/(PI*sin(x_i))),2);
        twos_sum = twos_sum + seq_twos;
    }

    temp_vals[1] = twos_sum;
    pthread_exit((void*) t);
    return EXIT_SUCCESS;
}

void* ends(void *t)
{
    long double a_n, a_0;
    long double x_n = n_slices;
    long double x_0 = 0;
    long tid = (long)t;
    pid_t end_to_end;
    printf("End to ends:: x_n ==%Lf \n",x_n);

    end_to_end = fork();
    if (end_to_end == 0)
    {
        x_0 = 0 * (PI / n_slices);
        a_0 = 1; 
        printf("a_0 :: %Lf :: x_0 :: %Lf\n",a_0, x_0);
        exit(1);
    }
    else
    {
        x_n = n_slices * (PI / n_slices);
        a_n = pow(((sin(PI*sin(x_n)))/(PI*sin(x_n))),2);
        printf("a_n :: %Lf || x_n :: %Lf\n",a_n, x_n);
        wait(NULL);
    }

    temp_vals[2] = a_0 + a_n;
    pthread_exit((void*) t);
    return EXIT_SUCCESS;
}


int main(int argc, char *argv[])
{

    pid_t id;
    pthread_t ends_thread, twos_and_threes[3];
    pthread_mutex_t thread_locker;
    void * status;
    long t;

    n_slices =(atof(argv[1])) ;
    n_slices = ((n_slices + 3 - 1) / 3) * 3 ;

    printf("Running with slice size :: %lf (must be multiple of 3)\n", n_slices);
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_mutex_init(&thread_locker, NULL);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
    //Child Process
    if(pthread_create(&twos_and_threes[0], &attr,ends,(void*) t))
        return EXIT_FAILURE;
    if(pthread_create(&twos_and_threes[1],&attr,twos,(void*)t))
        return EXIT_FAILURE;
    if(pthread_create(&twos_and_threes[2],&attr,threes,(void*)t))
        return EXIT_FAILURE;

    wait(NULL);
    pthread_attr_destroy(&attr);
    for(int i = 0 ; i < 3 ; i++)
        pthread_join(twos_and_threes[i], &status);

    /*
    twos();
    threes();
    ends(); 
    */

    temp_vals[3] = temp_vals[0]+temp_vals[1] +temp_vals[2];

    printf( "Temp vals :: %Lf :: %Lf :: %Lf :: %Lf\n",\
            temp_vals[0],temp_vals[1],temp_vals[2],temp_vals[3]);

    wait(NULL);

    long double result  =((3*(PI/ n_slices))/8)*(temp_vals[3]) ;
    printf("Result == %Lf \n",result);




    pthread_exit(NULL);

    return EXIT_SUCCESS;
}

Thank you, that solved that error, along with a few other changes, the code has been updated to reflect.

Answer 1

You are creating the threads in one process, then destroying them in a different process. When you fork() , only the thread that calls fork() will be present in the child, and threads created in the child will not magically appear in the parent.

You don't need fork() here as well as threads. Just wait for the threads to complete in the master thread.