LinuxQuestions.org - compiling a pthread program

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compiling a pthread program

am I am trying to compile a program whose code is as shown:

Code:

#include<pthread.h>



int sum1;

int sum2;



void thread1(int v[], int v_count) {

sum1 = 0;

int i;

for (i = 0; i < v_count; i++)

sum1 += v[i];

}

void thread2(int v[], int v_count) {

sum2 = 0;

int i;

for (i = 0; i < v_count; i++)

sum2 += v[i];

}





int main ( int argc, char** argv )

{

  pthread_t t1, t2;

  int N = 5000;

  int array1[N];

  

  pthread_create(&t1,NULL,thread1,array1,N);

  pthread_create(&t2,NULL,thread2,array1,N);

  pthread_join(t1,NULL);

    

}

The output is now shown:

Code:

gcc example2.c -o exam -lpthread -lm -lrt -g

example2.c: In function ‘main’:

example2.c:27: warning: passing argument 3 of ‘pthread_create’ from incompatible pointer type

/usr/include/pthread.h:225: note: expected ‘void * (*)(void *)’ but argument is of type ‘void (*)(int *, int)’

example2.c:27: error: too many arguments to function ‘pthread_create’

example2.c:28: warning: passing argument 3 of ‘pthread_create’ from incompatible pointer type

/usr/include/pthread.h:225: note: expected ‘void * (*)(void *)’ but argument is of type ‘void (*)(int *, int)’

example2.c:28: error: too many arguments to function ‘pthread_create’

I am trying to get two threads (thread1 and thread2) to run in parallell and thus create a problem of false sharing. I somehow cannot even get the program to compile.

I am sending each separate thread the same arguments. The array, array1, and the value of N. I think that this is the correct format. What am I doing wrong?

Any help appreciated. Thanks in advance.

Respectfully,

jyunker

Check out some of the examples here Pthread Examples.

You have to pass a void pointer, as the compiler is telling you. I don't think you can pass more than that one argument, you'd have to create a structure and cast it to the void pointer.

compiling a pthreads program

Okay here is my new code, I created a struct name arg_struct with my two arguments that and I will pass struct
to thread1 and thread2:

Code:



#include<pthread.h>



int sum1;

int sum2;



struct arg_struct  {

  int arg1;

  int arg2;

}; 





void thread1(int v[], int v_count) {

    

    struct arg_struct *args = (struct arg_struct *)args;

    sum1 = 0;

    int i;

    for (i = 0; i < v_count; i++) {

//  printf ( "%d ", i );

    sum1 += v[i];

}

}

void thread2(int v[], int v_count) {



    struct arg_struct *args = (struct arg_struct *)args;

    sum2 = 0; 

    int i;

    for (i = 0; i < v_count; i++) {

//  printf ( "%d ", i );

    sum2 += v[i];

}

}





int main ( int argc, char** argv )

{

  pthread_t t1, t2;

  int N = 5000;

  int array1[N];

  struct arg_struct args;

  args.arg1 = array1;

  args.arg2 = N;



  

  pthread_create(&t1,NULL,&thread1,(void *)&args));

  pthread_create(&t2,NULL,&thread2,(void *)&args));

  pthread_join(t1,NULL);

    

}

and when I run it, I get the following errors:

gcc example2.c -o exam -lpthread -lm -lrt -g
example2.c: In function ‘main’:
example2.c:41: warning: assignment makes integer from pointer without a cast
example2.c:45: warning: passing argument 3 of ‘pthread_create’ from incompatible pointer type
/usr/include/pthread.h:225: note: expected ‘void * (*)(void *)’ but argument is of type ‘void (*)(int *, int)’
example2.c:45: error: expected ‘;’ before ‘)’ token
example2.c:45: error: expected statement before ‘)’ token
example2.c:46: warning: passing argument 3 of ‘pthread_create’ from incompatible pointer type
/usr/include/pthread.h:225: note: expected ‘void * (*)(void *)’ but argument is of type ‘void (*)(int *, int)’
example2.c:46: error: expected ‘;’ before ‘)’ token
example2.c:46: error: expected statement before ‘)’ token

Now what am I doing wrong? This is my first time programming with pthreads and I am making too
many errors.

Any help appreciated. Thanks in advance.

Respectfully,

jyunker

You have fundamental syntax errors in there which have nothing to do with pthreads, they're just general errors in composing a C program. Read the output of the compiler errors and warnings, go to the lines it is complaining about, and fix your syntax errors.

I suggest you should review the p_greetings.c or p_cpi.c examples in the link previously sent.