001_ok_cow_initial.c

// compile with 
// gcc -O2 001_ok_cow_initial.c -o 001_ok_cow_initial -pthread -Wall -Wextra

#include <stdint.h>  // uint8_t
#include <string.h>  // memcmp
#include <pthread.h> // pthread_create, pthread_join, pthread_mutex_lock, pthread_mutex_unlock
#include <stdbool.h> // bool, true, false

#define xylen 1024

static uint8_t voxelGroups[321536][xylen];
static int threadCount = 4;
static int identicalVoxelGroupsCount = 0;

static pthread_mutex_t mutex;

bool areVoxelGroupsIdentical(uint8_t firstArray[xylen], uint8_t secondArray[xylen]){
    return memcmp(firstArray, secondArray, xylen*sizeof(uint8_t)) == 0;
}

void* getIdenticalVoxelGroupsCount(void* threadNumber){
    for(int i = (long)threadNumber-1; i < 321536-1; i += threadCount){
        for(int j = i+1; j < 321536; j++){
            if(areVoxelGroupsIdentical(voxelGroups[i], voxelGroups[j])){
                pthread_mutex_lock(&mutex);
                identicalVoxelGroupsCount++;
                pthread_mutex_unlock(&mutex);
            }
        }
    }
    return 0;
}

int main(){
    pthread_t thread1, thread2, thread3, thread4;
    pthread_mutex_init(&mutex, 0);
    pthread_create(&thread1, NULL, getIdenticalVoxelGroupsCount, (void *)1);
    pthread_create(&thread2, NULL, getIdenticalVoxelGroupsCount, (void *)2);
    pthread_create(&thread3, NULL, getIdenticalVoxelGroupsCount, (void *)3);
    pthread_create(&thread4, NULL, getIdenticalVoxelGroupsCount, (void *)4);
    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    pthread_join(thread3, NULL);
    pthread_join(thread4, NULL);
}