I am making a simulator for Round Robin scheduling algorithm in C. Right now I made it so that the time quantum is 2. So every 2 seconds it takes a "process" from the front of the list, reduces its remaining time by 2, and then sticks it to the end of the list and grabs the next one. Also, every second, it increases others' waiting time by 1. However when I try to remove the process from the front of the list (so I can put it in the end of the list) in function round_Robin(), it removes it. But it does not append it to the end of the linked list. What am I doing wrong? Thank you!
I am using command line arguments as so :
./a.out input.dat text.txt 5 0.4
And here is my input.dat:
1 0 10 50
2 2 0 40
3 3 20 50
4 4 7 35
5 5 10 50
6 6 0 40
7 7 20 50
8 9 7 35
9 10 10 50
10 12 0 40
And here is my code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define n 10
char *cRR;//get the argument for RR time
char *calpha;//get the argument for alpha
int full[40];
int arraylength;
int RR;//to hold RR time as an int
int i=0;//used to count amount of numbers in test file
double alpha;//hold alpha time as a double
int at[n];
int global_timer=-1;
typedef int LL_pid; // the pid of the PCB
typedef int LL_AT;//the arrival time of the pcb
typedef int LL_priority;//the priority of that PCB
typedef int LL_BT;//the Burst time of that PCB
typedef int LL_remainingtime;
typedef int LL_wT;
typedef struct LL PCB; //the PCB
struct LL //linked list structure(pcb)
{
LL_pid pid;
LL_AT AT;
LL_priority priority;
LL_BT BT;
LL_remainingtime RT;
LL_wT wT;
PCB *next;//points to next pcb in linked list
};
struct job//used for job queue
{
int pid2;
int AT2;
int priority2;
int BT2;
};
int LL_length(PCB *pcb_head); //linked list length
void LL_add(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT, LL_remainingtime RRT,LL_wT wTT); //adds PCB to front of list
void LL_pop(PCB **pcb_head); //removes the head from the list & returns its value
void LL_print(PCB **pcb_head); //prints all the processes
void LL_clear(PCB **pcb_head); //deletes all the processes from queue
void LL_append(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT,LL_remainingtime RRT,LL_wT wTT); //adds a process to the end of the list
int LL_elem(PCB **pcb_head, LL_pid d); //checks for the pcb via pid
void add_jobs(int jobss[]);
struct job jobs[n];//contains all the jobs an array
void counter(PCB **pcb_head);
void round_Robin(PCB **pcb_head);
int main ( int argc, char *argv[] )
{
PCB *pcb_head=NULL;
//*****START COMMAND LINE ARGS
if ( argc != 5 )//if they incorrectly inputed arguments
{
/* We print argv[0] assuming it is the program name */
printf( "usage: %s filename, output file name, RR quantum as a int, Alpha value as a float", argv[0] );
}
else
{
cRR=argv[3];//get arg for RR time
calpha=argv[4];//get arg for alpha
alpha=atof(calpha);//convert alpha to float
RR=atoi(cRR);//convert RR to int
// We assume argv[1] is a filename to open
FILE *file = fopen( argv[1], "r" );//open file which is 2nd arg
// fopen returns 0, the NULL pointer, on failure
if ( file == 0 )
{
printf( "Could not open file\n" );
} else
{
int y=0;//used for while loop below
while ( fscanf(file,"%d",&y)!=EOF )//scan file and find all the numbers
{
full[i]=y;//insert the numbers into an array
i++;
}
fclose( file );//done using the file
}
/*TEST PRINTING EVERYTHING IN FILE
int testprint=0;
for(testprint=0;testprint<i;testprint++){printf("%d\n",full[testprint]);}
printf("\nend of array check");*/
//write to file
FILE *fp;
fp = fopen(argv[2], "w+");
fprintf(fp, "This is testing for fprintf...\n");
fclose(fp);
}
/////////////////END OF COMMAND ARGUMENT THINGS
add_jobs(full);//adds all inputs from file to the array "jobs"
counter(&pcb_head);
round_Robin(&pcb_head);
/*
//example usage:
LL_add(&pcb_head, 7,7,7,7,10); //push value 7 onto stack
printf("%d\n", pcb_head -> pid); //show stack head value
LL_add(&pcb_head, 21,21,21,21,31); //push value 21 onto stack
LL_print(&pcb_head); //print the stack
if(LL_elem(&pcb_head, 7)) puts("found 7"); //does 7 belong to the stack?
LL_append(&pcb_head, 0,0,0,0,50); //append 0 to the end of the stack
LL_print(&pcb_head); //print the stack
LL_pop(&pcb_head); //pop the stack's head
LL_print(&pcb_head); //print the stack
LL_clear(&pcb_head); //clear the stack
LL_print(&pcb_head); //print the stack
*/
getchar();
return 0;
}
int LL_length(PCB *pcb_head)
{
PCB *curr = pcb_head;//set a temp value to the head
int len = 0;
while(curr)
{
++len;//increase length variable
curr = curr -> next;//go to next and keep looping to get whole length
}
return len;
}
void LL_add(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT, LL_remainingtime RRT, LL_wT wTT)
{
PCB *pcb_new = malloc(sizeof(PCB));//allocate memory for another structure (PCB)
pcb_new -> pid = ppid;//create a pcb with pid inserted
pcb_new -> AT = AAT;
pcb_new -> priority = ppriority;
pcb_new -> BT = BBT;
pcb_new -> RT = RRT;
pcb_new -> wT = wTT;
pcb_new -> next = *pcb_head;//set its next to the head(inserting in front of list)
*pcb_head = pcb_new;//set the pointer of head to it since it is in front of list now
}
void LL_pop(PCB **pcb_head)
{
PCB *pcb_temp = *pcb_head;
printf("\nProcess %d is terminating\n", pcb_temp->pid);
*pcb_head = pcb_temp -> next;
free(pcb_temp);
}
void LL_print(PCB **pcb_head)
{
PCB *pcb_temp = *pcb_head;
if(!pcb_temp)
puts("the list is empty");
else
{
// while(pcb_temp)
//{
printf("Process %d has terminated...", pcb_temp -> pid);// print all the pids
// printf("%d ", pcb_temp -> AT);
// printf("%d ", pcb_temp -> priority);
// printf("%d ", pcb_temp -> BT);
//pcb_temp = pcb_temp -> next;//loop to next pcb*/
//}
putchar('\n');
}
}
void LL_clear(PCB **pcb_head)
{
while(*pcb_head)//this will get every pcb as pop below sets head value to next after deleting it
LL_pop(pcb_head);
}
void LL_append(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT, LL_remainingtime RRT,LL_wT wTT)
{
PCB *pcb_temp = *pcb_head;//get head value
if(!pcb_temp)//if nothing in head value just add the pcb as list is empty
LL_add(pcb_head, ppid, AAT, ppriority, BBT, RRT, wTT);
else
{
while(pcb_temp -> next)//get the last pcb
pcb_temp = pcb_temp -> next;
LL_add(&(pcb_temp -> next), ppid, AAT, ppriority, BBT, RRT, wTT);//add it onto the last
}
}
void add_jobs(int jobss[]){
int i = 0;
int i2 = 1;
int i3 = 2;
int i4 = 3;
int x =0;
int x2=0;
int x3=0;
int x4=0;
while(x<10){
jobs[x].pid2=jobss[i];
x++;
i+=4;
}
while(x2<10){
jobs[x2].AT2=jobss[i2];
i2+=4;
x2++;
}
while(x3<10){
jobs[x3].priority2=jobss[i3];
i3+=4;
x3++;
}
while(x4<10){
jobs[x4].BT2=jobss[i4];
i4+=4;
x4++;
}
arraylength=x4;
}
//NEED TO CHANGE 2 TO THE REAL ROUND BOBIN QUANTUM, NEED TO ADD IF RT IS LESS THEN QUANTUM, THEN PRINT FOR RT
void round_Robin(PCB **pcb_head){
PCB *pcb_temp = *pcb_head;
PCB *next = (*pcb_head)->next;//get the next value since it will be the next head
int x;
//store all the heads values
int storepid = pcb_temp->pid;
int storeat = pcb_temp->AT;
int storepriority=pcb_temp->priority;
int storebt=pcb_temp->BT;
int storert=pcb_temp->RT;
int storewt=pcb_temp->wT;
for (x=0;x<100;x++){
if(*pcb_head){
int h=0;
for(h=0;h<2;h++){//2 is represented as the time quantum right now
printf("\nProcess %d is running", (*pcb_head)->pid);
counter(pcb_head);//even tho this increases wt we already stored original wt in storewt
}
LL_pop(pcb_head);//get rid of it from head
storert-=2;//its remaining time decreases
LL_append(&next,storepid,storeat,storepriority,storebt,storert,storewt);//append it to the list
}
else{
printf("....");
counter(pcb_head);}//run counter and see if any new processes
}
}
void counter(PCB **pcb_head){
int locator;
PCB *pcb_temp = *pcb_head;
global_timer++;//increase the time
printf("\nTIME %d:", global_timer);
for(locator=0;locator<10;locator++){
if (jobs[locator].AT2==global_timer){//see if any processes are ready to enter the ready queue linked list
LL_append(pcb_head,jobs[locator].pid2,jobs[locator].AT2,jobs[locator].priority2,jobs[locator].BT2,jobs[locator].BT2,0); }
}
while(pcb_temp){
pcb_temp-> wT +=1;//increase everyones waiting time in the linked list ready queue
pcb_temp = pcb_temp->next;
}
}
int LL_elem(PCB **pcb_head, LL_pid x)
{
PCB *pcb_temp = *pcb_head;//get head
while(pcb_temp)
{
if(pcb_temp -> pid == x) //set for numbers, modifiable
return 1;
else
pcb_temp = pcb_temp -> next;
}
return 0;
}
EDIT :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define n 10
char *cRR;//get the argument for RR time
char *calpha;//get the argument for alpha
int full[40];
int arraylength;
int RR;//to hold RR time as an int
int i=0;//used to count amount of numbers in test file
double alpha;//hold alpha time as a double
int at[n];
int global_timer=-1;
typedef int LL_pid; // the pid of the PCB
typedef int LL_AT;//the arrival time of the pcb
typedef int LL_priority;//the priority of that PCB
typedef int LL_BT;//the Burst time of that PCB
typedef int LL_remainingtime;
typedef int LL_wT;
typedef struct LL PCB; //the PCB
struct LL //linked list structure(pcb)
{
LL_pid pid;
LL_AT AT;
LL_priority priority;
LL_BT BT;
LL_remainingtime RT;
LL_wT wT;
PCB *next;//points to next pcb in linked list
};
struct job//used for job queue
{
int pid2;
int AT2;
int priority2;
int BT2;
};
int LL_length(PCB *pcb_head); //linked list length
void LL_add(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT, LL_remainingtime RRT,LL_wT wTT); //adds PCB to front of list
void LL_pop(PCB **pcb_head); //removes the head from the list & returns its value
void LL_print(PCB **pcb_head); //prints all the processes
void LL_clear(PCB **pcb_head); //deletes all the processes from queue
void LL_append(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT,LL_remainingtime RRT,LL_wT wTT); //adds a process to the end of the list
int LL_elem(PCB **pcb_head, LL_pid d); //checks for the pcb via pid
void add_jobs(int jobss[]);
struct job jobs[n];//contains all the jobs an array
void counter(PCB **pcb_head);
void round_Robin(PCB **pcb_head);
int main ( int argc, char *argv[] )
{
PCB *pcb_head=NULL;
//*****START COMMAND LINE ARGS
if ( argc != 5 )//if they incorrectly inputed arguments
{
/* We print argv[0] assuming it is the program name */
printf( "usage: %s filename, output file name, RR quantum as a int, Alpha value as a float", argv[0] );
}
else
{
cRR=argv[3];//get arg for RR time
calpha=argv[4];//get arg for alpha
alpha=atof(calpha);//convert alpha to float
RR=atoi(cRR);//convert RR to int
// We assume argv[1] is a filename to open
FILE *file = fopen( argv[1], "r" );//open file which is 2nd arg
// fopen returns 0, the NULL pointer, on failure
if ( file == 0 )
{
printf( "Could not open file\n" );
} else
{
int y=0;//used for while loop below
while ( fscanf(file,"%d",&y)!=EOF )//scan file and find all the numbers
{
full[i]=y;//insert the numbers into an array
i++;
}
fclose( file );//done using the file
}
/*TEST PRINTING EVERYTHING IN FILE
int testprint=0;
for(testprint=0;testprint<i;testprint++){printf("%d\n",full[testprint]);}
printf("\nend of array check");*/
//write to file
FILE *fp;
fp = fopen(argv[2], "w+");
fprintf(fp, "This is testing for fprintf...\n");
fclose(fp);
}
/////////////////END OF COMMAND ARGUMENT THINGS
add_jobs(full);//adds all inputs from file to the array "jobs"
counter(&pcb_head);
round_Robin(&pcb_head);
/*
//example usage:
LL_add(&pcb_head, 7,7,7,7,10); //push value 7 onto stack
printf("%d\n", pcb_head -> pid); //show stack head value
LL_add(&pcb_head, 21,21,21,21,31); //push value 21 onto stack
LL_print(&pcb_head); //print the stack
if(LL_elem(&pcb_head, 7)) puts("found 7"); //does 7 belong to the stack?
LL_append(&pcb_head, 0,0,0,0,50); //append 0 to the end of the stack
LL_print(&pcb_head); //print the stack
LL_pop(&pcb_head); //pop the stack's head
LL_print(&pcb_head); //print the stack
LL_clear(&pcb_head); //clear the stack
LL_print(&pcb_head); //print the stack
*/
getchar();
return 0;
}
int LL_length(PCB *pcb_head)
{
PCB *curr = pcb_head;//set a temp value to the head
int len = 0;
while(curr)
{
++len;//increase length variable
curr = curr -> next;//go to next and keep looping to get whole length
}
return len;
}
void LL_add(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT, LL_remainingtime RRT, LL_wT wTT)
{
PCB *pcb_new = malloc(sizeof(PCB));//allocate memory for another structure (PCB)
pcb_new -> pid = ppid;//create a pcb with pid inserted
pcb_new -> AT = AAT;
pcb_new -> priority = ppriority;
pcb_new -> BT = BBT;
pcb_new -> RT = RRT;
pcb_new -> wT = wTT;
pcb_new -> next = NULL;//set its next to the head(inserting in front of list)
*pcb_head = pcb_new;//set the pointer of head to it since it is in front of list now
}
void LL_pop(PCB **pcb_head)
{
PCB *pcb_temp = *pcb_head;
printf("\nProcess %d is terminating\n", pcb_temp->pid);
*pcb_head = pcb_temp -> next;
free(pcb_temp);
}
void LL_print(PCB **pcb_head)
{
PCB *pcb_temp = *pcb_head;
if(!pcb_temp)
puts("the list is empty");
else
{
// while(pcb_temp)
//{
printf("Process %d has terminated...", pcb_temp -> pid);// print all the pids
// printf("%d ", pcb_temp -> AT);
// printf("%d ", pcb_temp -> priority);
// printf("%d ", pcb_temp -> BT);
//pcb_temp = pcb_temp -> next;//loop to next pcb*/
//}
putchar('\n');
}
}
void LL_clear(PCB **pcb_head)
{
while(*pcb_head)//this will get every pcb as pop below sets head value to next after deleting it
LL_pop(pcb_head);
}
void LL_append(PCB **pcb_head,LL_pid ppid, LL_AT AAT, LL_priority ppriority, LL_BT BBT, LL_remainingtime RRT,LL_wT wTT)
{
PCB *pcb_temp = *pcb_head;//get head value
if(!pcb_temp)//if nothing in head value just add the pcb as list is empty
LL_add(pcb_head, ppid, AAT, ppriority, BBT, RRT, wTT);
else
{
while(pcb_temp -> next)//get the last pcb
pcb_temp = pcb_temp -> next;
LL_add(&(pcb_temp -> next), ppid, AAT, ppriority, BBT, RRT, wTT);//add it onto the last
}
}
void add_jobs(int jobss[]){
int i = 0;
int i2 = 1;
int i3 = 2;
int i4 = 3;
int x =0;
int x2=0;
int x3=0;
int x4=0;
while(x<10){
jobs[x].pid2=jobss[i];
x++;
i+=4;
}
while(x2<10){
jobs[x2].AT2=jobss[i2];
i2+=4;
x2++;
}
while(x3<10){
jobs[x3].priority2=jobss[i3];
i3+=4;
x3++;
}
while(x4<10){
jobs[x4].BT2=jobss[i4];
i4+=4;
x4++;
}
arraylength=x4;
}
//NEED TO CHANGE 2 TO THE REAL ROUND BOBIN QUANTUM, NEED TO ADD IF RT IS LESS THEN QUANTUM, THEN PRINT FOR RT
void round_Robin(PCB **pcb_head){
int x;
for (x=0;x<250;x++){
PCB *pcb_temp = *pcb_head;
PCB *next = (*pcb_head)->next;//get the next value since it will be the next head
int storepid = pcb_temp->pid;
int storeat = pcb_temp->AT;
int storepriority=pcb_temp->priority;
int storebt=pcb_temp->BT;
int storert=pcb_temp->RT;
int storewt=pcb_temp->wT;
if(*pcb_head){//if there is something in the list
int h=0;
if(storert>=2){//if the remaining time is greater than the quantum
for(h=0;h<2;h++){//2 is represented as the time quantum right now
printf("\nProcess %d is running", (*pcb_head)->pid);
counter(pcb_head);//even tho this increases wt we already stored original wt in storewt
//print it for the quantum
}
LL_pop(pcb_head);//get rid of it from head
storert-=2;//its remaining time decreases by the quantum
if(storert>0){//if it still has remaining time append it
LL_append(&next,storepid,storeat,storepriority,storebt,storert,storewt);}//append it to the list}
else{printf("Process has finished");}//if it doesnt type it finished
}
else{//if the remaining time is less then the quantum
for(h=0;h<storert;h++){//do it for how much is remaining
printf("\nProcess %d is running", (*pcb_head)->pid);
counter(pcb_head);
}
LL_pop(pcb_head);//get rid of it from head because it finished
printf("Process has finished");
}
}
else{
printf("....");
counter(pcb_head);}//run counter and see if any new processes
}
}
void counter(PCB **pcb_head){
int locator;
PCB *pcb_temp = *pcb_head;
global_timer++;//increase the time
printf("\nTIME %d:", global_timer);
for(locator=0;locator<10;locator++){
if (jobs[locator].AT2==global_timer){//see if any processes are ready to enter the ready queue linked list
LL_append(pcb_head,jobs[locator].pid2,jobs[locator].AT2,jobs[locator].priority2,jobs[locator].BT2,jobs[locator].BT2,0); }
}
while(pcb_temp){
pcb_temp-> wT +=1;//increase everyones waiting time in the linked list ready queue
pcb_temp = pcb_temp->next;
}
}
int LL_elem(PCB **pcb_head, LL_pid x)
{
PCB *pcb_temp = *pcb_head;//get head
while(pcb_temp)
{
if(pcb_temp -> pid == x) //set for numbers, modifiable
return 1;
else
pcb_temp = pcb_temp -> next;
}
return 0;
}
This code:
PCB *pcb_temp = *pcb_head;
PCB *next = (*pcb_head)->next;//get the next value since it will be the next head
//store all the heads values
int storepid = pcb_temp->pid;
int storeat = pcb_temp->AT;
int storepriority=pcb_temp->priority;
int storebt=pcb_temp->BT;
int storert=pcb_temp->RT;
int storewt=pcb_temp->wT;
needs to be done on every loop not just once before the loop. Otherwise you will keep appending the same item to the end instead of the current head item.
Also, LL_add() can't be used to append to the list because it always assumes it is adding to the head:
pcb_new -> next = *pcb_head;
*pcb_head = pcb_new;
If you are appending to the tail, you need code that looks like this:
pcb_new -> next = NULL;
*tail_ptr = pcb_new;
Edit:
It seems that LL_add() is only ever used to append to the tail and not the head. In that case, just change this line:
pcb_new -> next = *pcb_head;
to this:
pcb_new -> next = NULL;
However, if you do make this change, then don't try to insert to the head using this modified version because it won't work.