How to run the following C program "Seeking Tutor" on Linux - c

Question

I have a C program. I want to run it on Linux. But, when I am entering gcc seekingtutor.c -o seek I am getting error. And, sometimes its showing file not exists on the directory. Is there any way I can run this program?
Code is here in GitHub
I want to run the following code on linux terminal. I am seeking for the command it needs to run. I think pthread compiling is needed.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
#include <assert.h>
//maximum student numbers
#define Max_stu_size 2000
//const int Max_stu_size=2000;
//check how many students have done.
//then coordinate and tutors threads can terminate
int done=0;
int totalRequests=0;
int totalSessions=0;
int tutoringNow=0;
void *student_thread(void *student_id);
void *tutor_thread(void *tutor_id);
void *coordinator_thread();
//void *coordinator_thread(void *);
int student_num=0;
int tutor_num=0;
int help_num=0;
int chair_num=0;
int occupied_chair_num=0;
int newArrivedStudentQueue[Max_stu_size];
int tutorFinishedQueue[Max_stu_size];
int priorityQueue[Max_stu_size][2];
int student_priority[Max_stu_size];
int student_ids[Max_stu_size];
int tutor_ids[Max_stu_size];
sem_t sem_student;
sem_t sem_coordinator;
//sem_t sem_tutorToStudent[Max_stu_size];
pthread_mutex_t seatLock;
pthread_mutex_t queueLock;
pthread_mutex_t tutorFinishedQueueLock;
int main(int argc, const char * argv[]) {
//test
/*student_num=10;
tutor_num=3;
chair_num=4;
help_num=5;*/
//get input argument
if (argc != 5){
printf("Usage: <# of Students> <# of tutors> <# of chairs> <# of help>\n");
exit(-1);
}
student_num=atoi(argv[1]);
tutor_num=atoi(argv[2]);
chair_num=atoi(argv[3]);
help_num=atoi(argv[4]);
if(student_num > Max_stu_size || tutor_num > Max_stu_size){
printf("Max student number is: %d; Max tutor number is: %d\n", Max_stu_size, Max_stu_size);
exit(-1);
}
//init arrays
int i;
for(i=0;i<student_num;i++){
newArrivedStudentQueue[i]=-1;
tutorFinishedQueue[i]=-1;
priorityQueue[i][0]=-1;
priorityQueue[i][1]=-1;
student_priority[i]=0;
}
//init lock and semaphore
sem_init(&sem_student,0,0);
sem_init(&sem_coordinator,0,0);
pthread_mutex_init(&seatLock,NULL);
pthread_mutex_init(&queueLock,NULL);
pthread_mutex_init(&tutorFinishedQueueLock,NULL);
/*for(i=0;i<student_num;i++){
sem_init(&sem_tutorToStudent[i],0,0);
}*/
//allocate threads
pthread_t students[student_num];
pthread_t tutors[tutor_num];
pthread_t coordinator;
//create threads
assert(pthread_create(&coordinator,NULL,coordinator_thread,NULL)==0);
for(i = 0; i < student_num; i++)
{
student_ids[i] = i + 1;
assert(pthread_create(&students[i], NULL, student_thread, (void*) &student_ids[i])==0);
}
for(i = 0; i < tutor_num; i++)
{
tutor_ids[i] = i + student_num + 1;
assert(pthread_create(&tutors[i], NULL, tutor_thread, (void*) &tutor_ids[i])==0);
}
//join threads
pthread_join(coordinator, NULL);
for(i =0; i < student_num; i++)
{
pthread_join(students[i],NULL);
}
for(i =0; i < tutor_num; i++)
{
pthread_join(tutors[i],NULL);
}
return 0;
}
//students action.
//1.program;
//2.find the empty seat and nofity coordinator;
//3.wait tutor to wake it up and finish tutoring.
void *student_thread(void *student_id){
int id_student=*(int*)student_id;
while(1){
if(student_priority[id_student-1]>=help_num) {
pthread_mutex_lock(&seatLock);
done++;
pthread_mutex_unlock(&seatLock);
//notify coordinate to terminate
sem_post(&sem_student);
//printf("------student %d terminate------\n",id_student);
pthread_exit(NULL);
}
//programing
//sleeping for a random amount of time up to 2 ms
float programTime=(float)(rand()%200)/100;
//printf("sleep time = %f.\n", programTime);
usleep(programTime);
pthread_mutex_lock(&seatLock);
if(occupied_chair_num>=chair_num){
//St: Student x found no empty chair. Will try again later
printf("St: Student %d found no empty chair. Will try again later.\n",id_student);
pthread_mutex_unlock(&seatLock);
continue;
}
occupied_chair_num++;
totalRequests++;
newArrivedStudentQueue[id_student-1]=totalRequests;
//St: Student x takes a seat. Empty chairs = <# of empty chairs>.
printf("St: Student %d takes a seat. Empty chairs = %d\n",id_student,chair_num-occupied_chair_num);
pthread_mutex_unlock(&seatLock);
//notify coordinator that student seated.
sem_post(&sem_student);
//wait to be tutored.
while(tutorFinishedQueue[id_student-1]==-1);
//sem_wait(&sem_tutorToStudent[id_student-1]);
//St: Student x received help from Tutor y.
printf("St: Student %d received help from Tutor %d.\n",id_student,tutorFinishedQueue[id_student-1]-student_num);
//reset the shared data
pthread_mutex_lock(&tutorFinishedQueueLock);
tutorFinishedQueue[id_student-1]=-1;
pthread_mutex_unlock(&tutorFinishedQueueLock);
//tutored times++ after tutoring.
pthread_mutex_lock(&seatLock);
student_priority[id_student-1]++;
pthread_mutex_unlock(&seatLock);
}
}
//tutors action
//1.wait coordinator's nofitication;
//2.find student from queue with highest priority;
//3.tutoring and notify student it's done;
void *tutor_thread(void *tutor_id){
int id_tutor=*(int*)tutor_id;
int studentTutoredTimes;
//students with same tutored times, who come first has higher priority
int studentSequence;
int id_student;
while(1){
//if all students finish, tutors threads terminate.
if(done==student_num){
//printf("------tutor %d terminate------\n",id_tutor);
pthread_exit(NULL);
}
studentTutoredTimes=help_num-1;
studentSequence=student_num*help_num+1;
id_student=-1;
//wait coordinator's notification
sem_wait(&sem_coordinator);
pthread_mutex_lock(&seatLock);
//find student with highest priority from priority queue;
//if students with same tutored times, who come first has higher priority
int i;
for(i=0;i<student_num;i++){
if(priorityQueue[i][0]>-1 && priorityQueue[i][0]<=studentTutoredTimes
&& priorityQueue[i][1]<studentSequence){
studentTutoredTimes=priorityQueue[i][0];
studentSequence=priorityQueue[i][1];
id_student=student_ids[i];
}
}
//in case no student in the queue.
if(id_student==-1) {
pthread_mutex_unlock(&seatLock);
continue;
}
//pop the student(reset the priority queue)
priorityQueue[id_student-1][0]=-1;
priorityQueue[id_student-1][1]=-1;
//occupied chair--
occupied_chair_num--;
//all the students who are receiving tutoring now, since each tutor time slice is very tiny, so it's common that the tutoringNow is 0.
tutoringNow++;
pthread_mutex_unlock(&seatLock);
//tutoring
// sleeping for a random amount of time up to 0.2 ms
float tutorTime=(float)(rand()%200)/1000;
usleep(tutorTime);
//after tutoring
pthread_mutex_lock(&seatLock);
//need to do tutoringNow-- after tutoring.
tutoringNow--;
totalSessions++;
printf("Tu: Student %d tutored by Tutor %d. Students tutored now = %d. Total sessions tutored = %d\n",id_student,id_tutor-student_num,tutoringNow,totalSessions);
pthread_mutex_unlock(&seatLock);
//update shared data so student can know who tutored him.
pthread_mutex_lock(&tutorFinishedQueueLock);
tutorFinishedQueue[id_student-1]=id_tutor;
pthread_mutex_unlock(&tutorFinishedQueueLock);
//wake up the tutored student.
//sem_post(&sem_tutorToStudent[id_student-1]);
}
}
//coordinator action.
//1.wait student's nofitication;
//2.push student into the queue with priority;
//3.notify tutor
void *coordinator_thread(){
while(1){
//if all students finish, tutors threads and coordinate thread terminate.
if(done==student_num){
//terminate tutors first
int i;
for(i=0;i<tutor_num;i++){
//notify tutors to terminate
sem_post(&sem_coordinator);
}
//terminate coordinate itself
//printf("------coordinator terminate------\n");
pthread_exit(NULL);
}
//wait student's notification
sem_wait(&sem_student);
pthread_mutex_lock(&seatLock);
//find the students who just seated and push them into the priority queue
int i;
for(i=0;i<student_num;i++){
if(newArrivedStudentQueue[i]>-1){
priorityQueue[i][0]=student_priority[i];
priorityQueue[i][1]=newArrivedStudentQueue[i];
printf("Co: Student %d with priority %d in the queue. Waiting students now = %d. Total requests = %d\n",student_ids[i],student_priority[i],occupied_chair_num,totalRequests);
newArrivedStudentQueue[i]=-1;
//notify tutor that student is in the queue.
sem_post(&sem_coordinator);
}
}
pthread_mutex_unlock(&seatLock);
}
}
Error:
gcc seekingtutor.c -o seek
/usr/bin/ld: /tmp/ccsL8SkI.o: in function `main':
seekingtutor.c:(.text+0x1a2): undefined reference to `sem_init'
/usr/bin/ld: seekingtutor.c:(.text+0x1b8): undefined reference to `sem_init'
/usr/bin/ld: seekingtutor.c:(.text+0x38e): undefined reference to `pthread_create'
/usr/bin/ld: seekingtutor.c:(.text+0x41c): undefined reference to `pthread_create'
/usr/bin/ld: seekingtutor.c:(.text+0x4c5): undefined reference to `pthread_create'
/usr/bin/ld: seekingtutor.c:(.text+0x50c): undefined reference to `pthread_join'
/usr/bin/ld: seekingtutor.c:(.text+0x530): undefined reference to `pthread_join'
/usr/bin/ld: seekingtutor.c:(.text+0x563): undefined reference to `pthread_join'
/usr/bin/ld: /tmp/ccsL8SkI.o: in function `student_thread':
seekingtutor.c:(.text+0x60d): undefined reference to `sem_post'
/usr/bin/ld: seekingtutor.c:(.text+0x722): undefined reference to `sem_post'
/usr/bin/ld: /tmp/ccsL8SkI.o: in function `tutor_thread':
seekingtutor.c:(.text+0x866): undefined reference to `sem_wait'
/usr/bin/ld: /tmp/ccsL8SkI.o: in function `coordinator_thread':
seekingtutor.c:(.text+0xad7): undefined reference to `sem_post'
/usr/bin/ld: seekingtutor.c:(.text+0xafc): undefined reference to `sem_wait'
/usr/bin/ld: seekingtutor.c:(.text+0xc08): undefined reference to `sem_post'
collect2: error: ld returned 1 exit status

Answer 1

$ ./seekingtutor
bash: ./seekingtutor: No such file or directory
While executing, you need to run it using ./seek, not ./seekingtutor as -o seek outputs the executable with the name seek
The linker has shown errors collect2: error: ld returned 1 exit status, so it did not output the executable.
It seems like it needs pthread. So run gcc seekingtutor.c -o seek -lpthread to compile it, and try. It works for me here.
https://man7.org/linux/man-pages/man3/sem_init.3.html says
Link with -pthread.