Struct thread c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>

#define MAX_LEN 10

struct PARAMDATA
{
    double k;
    int delay;
};

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_t tVisualizza, tMoltiplica1, tMoltiplica2;

int vet[MAX_LEN];
int esci;

void *visualizza()
{
    int i = 0;
    while (!esci)
    {
        pthread_mutex_lock(&mutex);
        printf("VET:\n");
        for (i = 0;i<MAX_LEN;i++)
            printf("%d\t", vet[i]);
        printf("\n");
        pthread_mutex_unlock(&mutex);
        usleep(500*1000);
    }
}

void *moltiplica(void* args)
{
    struct PARAMDATA *param = (struct PARAMDATA*)args;
    int i;
    while (!esci)
    {
        pthread_mutex_lock(&mutex);
        for (i = 0;i<MAX_LEN;i++)
            vet[i] = vet[i]*(*param).k;
        pthread_mutex_unlock(&mutex);
        usleep((*param).delay*1000);
    }
}

int main()
{
    int i = 0;

    for (i = 0; i < MAX_LEN; i++)
        if (i%2==0)
            vet[i] = 1;
        else
            vet[i] = -1;

    struct PARAMDATA *param1 = malloc(sizeof(struct PARAMDATA));
    (*param1).k=2;
    (*param1).delay=250;

    struct PARAMDATA *param2 = malloc(sizeof(struct PARAMDATA));
    (*param2).k = -2;
    (*param2).delay=900;

    esci = 0;

    pthread_create(&tVisualizza, NULL, visualizza, NULL);
    pthread_create(&tMoltiplica1, NULL, moltiplica, (void *)param1);
    pthread_create(&tMoltiplica2, NULL, moltiplica, (void *)param2);

    usleep(10*1000*1000);

    esci = 1;

    pthread_join(tVisualizza, NULL);
    pthread_join(tMoltiplica1, NULL);
    pthread_join(tMoltiplica2, NULL);
}