Rearrange Matrix using threads - c

Question

I`m trying to do this program, that taking matrix 4X4, and then creating 4 threads, and in parallel inserting the 4X4 matrix into array of 16 integer, sorting like this. odd number will go to odd index, and even number to even index in the array.
2 1 10 9 4 ec`
for example
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
will looks something like this:
The arranged array:
2 1 10 9 4 3 12 11 6 5 14 13 8 7 16 15
Num 2 was found by thread 0
Num 1 was found by thread 2
Num 10 was found by thread 1
Num 9 was found by thread 3
Num 4 was found by thread 0
Num 3 was found by thread 2
Num 12 was found by thread 1
Num 11 was found by thread 3
Num 6 was found by thread 0
Num 5 was found by thread 2
Num 14 was found by thread 1
Num 13 was found by thread 3
Num 8 was found by thread 0
Num 7 was found by thread 2
Num 16 was found by thread 1
Num 15 was found by thread 3
Now I came up with this code, but for some reason I'm not using all the threads like in the sample. I mean in the sample there is thread 0 then 2 then 1 then 3 etc. very mixed. I'm from other hand getting thread 0, thread 0, thread 0, 3, 3 ,0,0 etc.
How can I fix this?
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#define MAX 4
#define MAX_THREAD 4
int i = 0;
int newmatrix[16];
int oldmatrix[MAX][MAX] =
{1, 2, 3, 4,
5, 6, 7, 8,
9, 10, 11, 12,
13, 14, 15, 16};
int isUsed(int num)
{
for (int p = 0; p < 16; p++)
if (newmatrix[p] == num)
return 0;
return 1;
}
void *printHello(void *threadid)
{
int j, k;
long tid;
tid = (long)threadid;
while (i < 16)
{
sleep(0.01);
for (j = 0; j < 4; j++)
{
for (k = 0; k < 4; k++)
{
if (oldmatrix[j][k] % 2 == 0 && isUsed(oldmatrix[j][k]))
{
newmatrix[i] = oldmatrix[j][k];
printf("Num %d was found by thread %ld\n", oldmatrix[j][k], tid);
i++;
}
else if (isUsed(oldmatrix[j][k]))
{
newmatrix[i] = oldmatrix[j][k];
printf("Num %d was found by thread %ld\n", oldmatrix[j][k], tid);
i++;
}
}
}
}
if (tid == 1)
{
sleep(2);
printf("Hello There! thread %ld \n\n", tid);
for (int p = 0; p < 16; p++)
printf("%d ", newmatrix[p]);
}
pthread_exit(NULL);
}
int main(int argc, char const *argv[])
{
pthread_t threads[MAX_THREAD];
int rc;
long t;
for (t = 0; t < MAX_THREAD; t++)
{
rc = pthread_create(&threads[t], NULL, printHello, (void *)t);
if (rc)
{
printf("ERORR; return code from pthread_create() is %d\n", rc);
exit(EXIT_FAILURE);
}
}
pthread_exit(NULL);
}