array and vector multiplication using threads c language - c

Question

I'm writing a program that uses threads to compute the production of an array by a one dimensional array, all dimensions equal "n".
Each thread must compute the production of a row of the array with that one dimensional array.
The output i'm getting seems to have got addresses values instead of the values i already entered as the matrix elements.
What am i doing wrong?
here's the code i wrote:
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define mat_dim 5
static struct param
{
int mat[mat_dim][mat_dim];
int vec[mat_dim];
int ind;
int alter[mat_dim];
};
void *Calculate_row(struct param tid)
{
int i;
for (i=0; i<5; i++) {
tid.alter[tid.ind] = tid.alter[tid.ind]+tid.mat[tid.ind][i]*tid.vec[i];
}
pthread_exit((void *)&tid);
}
int main (int argc, char *argv[])
{
pthread_t thread[mat_dim];
pthread_attr_t attr;
int rc;
long t;
void *status;
int th_array[5][5]={{1,4,3,5,1},{4,6,2,8,5},{3,5,1,3,6},{1,5,6,2,8},{4,7,5,3,6}};
int th_vec[5]={1,2,1,2,1};
struct param thread_parameter;
thread_parameter.mat[5][5]=th_array;
thread_parameter.vec[5]=th_vec;
int tmp[5]={0,0,0,0,0};
thread_parameter.alter[5]=tmp;
/* Initialize and set thread detached attribute */
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
for(t=0; t<mat_dim; t++) {
printf("Main: creating thread %ld\n", t);
thread_parameter.ind=t;
rc = pthread_create(&thread[t], &attr, Calculate_row,&thread_parameter);
if (rc) {
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
}
/* Free attribute and wait for the other threads */
pthread_attr_destroy(&attr);
printf("the result vector is : ");
for(t=0; t<mat_dim; t++) {
rc = pthread_join(thread[t], NULL);
if (rc) {
printf("ERROR; return code from pthread_join() is %d\n", rc);
exit(-1);
}
printf("%d, ",thread_parameter.alter[t]);
}
printf("Main: program completed. Exiting.\n");
pthread_exit(NULL);
}

Answer 1

you are calling rc = pthread_create(&thread[t], &attr, Calculate_row,&thread_parameter);
where
struct param thread_parameter;
and the function is void *Calculate_row(struct param tid)
it should be void *Calculate_row(struct param *tid)
as a pointer is passed and change all . to ->.

Answer 2

All these lines:
thread_parameter.mat[5][5]=th_array;
thread_parameter.vec[5]=th_vec;
thread_parameter.alter[5]=tmp;
are wrong. The array indexes go from 0 to 4, therefore by addressing the 5th element you're out of their bounds.
You're using pthread_create the wrong way. This is the prototype:
int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
void *(*start_routine) (void *), void *arg);
Your Calculate_row receives a void* as a parameter, which needs to be cast to a (struct param *) and then dereferenced.