I am trying to write a program with threads, but i think i am not fully understanding them. I've been studying and working on the code for 8 hours straight and my head blocked. This is my task: i have 5 workers (threads) and i must use them to gather resources so i can build barracks and train 20 soldiers. SOldiers and barracks cost resources, so i must first gather resources in order to train a solder and/or build a barrack. I must use condVars and mutexes to protect the data and sync the threads (this i think is the hardest for me). This is my code so far:
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#define MAXCOUNT 100
pthread_mutex_t the_mutex;
pthread_mutex_t the_mutex_base;
pthread_cond_t condp, condc;
int allResources = 4096;
int gatheredResouerces = 0;
int soldiers=0;
int barracks = 0;
void* work(void* ptr){
size_t thread_num = (size_t)ptr;
while(1){
if(allResources>0&&(soldiers+5)<MAXCOUNT){
getResources(thread_num);
transport(thread_num);
unload(thread_num);
}
else{
printf("NOt enough resources...Quitting");
break;
}
}
}
void getResources(size_t thread){
printf("Worker %zd is searching...\n",thread);
pthread_mutex_lock(&the_mutex);
pthread_cond_wait(&condp,&the_mutex);
// while (gatheredResouerces != 0)
// pthread_cond_wait(&condp, &the_mutex);
gatheredResouerces+=5;
allResources-=5;
//pthread_cond_broadcast(&condc);
pthread_mutex_unlock(&the_mutex);
//pthread_cond_timedwait(&condp, &the_mutex,3);
return 0;
}
void build(size_t thread){
printf("Worker %zd is building a barrack",thread);
pthread_mutex_lock(&the_mutex);
while (gatheredResouerces == 0);
pthread_cond_wait(&condc, &the_mutex);
barracks++;
gatheredResouerces-=100;
pthread_mutex_unlock(&the_mutex);
sleep(20);
printf("worker %zd completed new building\n",thread);
return 0;
}
void transport(size_t thread){
printf("Worker %zd is transporting\n",thread);
pthread_mutex_lock(&the_mutex_base);
sleep(3);
pthread_mutex_unlock(&the_mutex_base);
}
void unload(size_t thread){
printf("Worker %zd unloaded resources\n",thread);
sleep(1);
return 0;
}
int main(int argc, char **argv)
{
pthread_t threads[5];
pthread_mutex_init(&the_mutex, NULL);
pthread_cond_init(&condp, NULL);
pthread_cond_init(&condc, NULL);
for(int i=0;i<5;i++){
int errorOne = pthread_create(&threads[i], NULL,work,(void*)i);
if (errorOne != 0) {
printf("Error creating thread %zd: error");
}
}
for (int i = 0; i<5; i++) {
printf("Waiting for thread %d to finish..\n", i);
int error = pthread_join(threads[i], NULL);
if (error != 0) {
printf("Error joining thread %zd: error:",threads[i]);
}
}*/
pthread_exit(NULL);
printf("\t\t\t...GAME INFORMATION...\n");
printf("gathered resources:%d\n",gatheredResouerces);
printf("Initial resources:%d\n",allResources);
printf("Resources left:%d",allResources-gatheredResouerces);
return 0;
}
I am very new to programming, so i am absolutely sure that so far my code is rubbish. Obviously it is not working, most of the times one thread gets to the work function and i get a segmantation fault. Some more on the condition: Workers must unload the resources in a command base and only one can do it at a time. I did not fully understand how to do this, is it a condVar that i lock and unlock in order to "unload resources"? Also, i am pretty sure i am screwing all the functions and not using these threads and mutexes properly, i read everything about threads, but all the examples are pretty easy - just for example a print function and a main function with 2-3 threads. I have no idea how to sync all these threads and make them do all these things. Also, if we type S or B worker should start either Building a barrack, or train a Soldier - this i also do not know how achieve, because it is undependable of the worker's process. What i mean is during the time worker is "working" if we type B or W if there are resources available worker should jump to other function - either Build or Train(which i havent written yet), if we dont have resources, worker should continue his resource gathering. I will be very happy if someone enlighten me where i am wrong, i know there are probably alot of mistakes, but i am really trying to learn. Thank you. Here is an example of a working program:
Game begins! Worker 1 is searching
Worker 1 is transporting
Worker 1 unloaded resources to Base station
Worker 2 is searching
Worker 2 is transporting
Worker 2 unloaded resources to Base station W Operation not supported
Worker 3 is searching
Worker 3 is transporting
Worker 3 unloaded resources to Base station
….. b Not enough resources
Worker 4 is searching
Worker 4 is transporting
Worker 4 unloaded resources to Base station … b Worker 3 is constructing new building barracks
Worker 2 is searching
Worker 2 is transporting
Worker 2 unloaded resources to Base station
…. Worker 3 completed new building barracks w
Warrior is being trained Worker 3 is searching
Warrior is ready for duty
...
