Find max in array with thread

#include <stdio.h>
#include <pthread.h>
#include <math.h>

typedef struct {
    int **startat;
    int *docount;
} thread_arg;

/* This is our thread function.  It is like main(), but for a thread*/
int *threadFunc(void *args)
{
    thread_arg *aargs = args;
    int erg = 0;
    for (int i = 0; i < aargs->docount; ++i) {
        if(aargs->startat + i > erg) {
            erg = aargs->startat + i;
        }
    }
    free(aargs);

    return erg;
}

int main(void)
{
    int length = 100;
    int in[length];
    for (int i = 0;i < length; ++i) {
        in[i] = rand();
    }
    int threads = (int) 1+sqrt(length-10); // we want to use sqrt(length) threads in an ideal szenario without slowdown when creating them. 10 is a threshhold for this
    int threadstepsize = (int) 1+length/threads;

    int ret = -1;

    pthread_t * thread = malloc(sizeof(pthread_t)*threads);

    for (int i = 0; i < threads; ++i) {
        thread_arg *args = malloc(sizeof *args);
        args->startat = in[i*threadstepsize];
        args->docount = &threadstepsize;
        ret = pthread_create(&thread[i], NULL, threadFunc, args);

        if(ret != 0) {
            printf ("Create pthread error!\n");
            exit (1);
        }
    }
    printf("main waiting for threads to terminate...\n");
    int out[threads];
    for (int i = 0; i < threads; ++i) {
        pthread_join(thread[i],out[i]);
    }
    thread_arg *args = malloc(sizeof *args);
    args->startat = &out;
    args->docount = &threads;
    int erg = threadFunc(args);
    printf("max is %d\n",erg);

    return 0;
}