为什么我的循环代码不能正常工作？ [英] Why isn't my round robin code working properly?
问题描述
我正在开发一个项目，我必须使用循环链表在c ++代码中实现Round Robin算法
。我真的不明白我在互联网上找到的代码，所以我决定自己做这些。算法很容易理解，但我似乎无法意识到我的代码中出错了什么：
I'm working on a project in which I have to implement the Round Robin algorithm
in a c++ code using a circular linked list. I didn't really understand the codes I found on the internet so I decided to do it all myself. The algorithm is easy to understand, but I can't seem to realize what am I doing wrong in my code:
#include<iostream>
#include<cstring>
using namespace std;
struct Nod{
char nameProc[100];
int arrivalT;
int burstT;
Nod *next;
};
Nod *head = NULL;
Nod *tail = NULL;
struct process
{
char nameProcess[100];
int arrival_Time;
int burst_Time;
int inList;
};
void deleteHead (Nod *&head)
{
Nod* toDelete = head;
head = head->next;
delete toDelete;
return;
}
void addArrivals(int time,Nod *&head,struct process p[],int n){
int i;
for(i=0;i<n;i++){
if((p[i].arrival_time<=time)&&(p[i].inlist==0)) {
="" if(head="=NULL)" if="" the="" list="" is="" empty
="" {
="" head="new" nod;="" memory="" for="" first="" one
="" strcpy(head-="">nameProc,p[i].nameProcess);
head->arrivalT = p[i].arrival_Time;
head->burstT = p[i].burst_Time;
head->next = head; // It's the only one, so it's connected to itself
tail =head; // and it is tail also
p[i].inList=1;
}
else // the list is not empty
{ Nod * nod = new Nod; // memory for a new one
strcpy(nod->nameProc,p[i].nameProcess); // put the data in it
nod->arrivalT = p[i].arrival_Time;
nod->burstT = p[i].burst_Time;
nod->next = head; // link tail to the head
tail->next = nod; // the ex tail is linked to the new one
tail = nod; // the new one is tail now
p[i].inList=1;
}
}
}
return;
}
void exeProc(Nod *&head, int quantum,int &time) //execution of the process
{ tail=head; // the ex head becomes tail (who's been interrupted goes to the end)
head=head->next; // and the next one becomes head
if(head->burstT>quantum) { //bt>quantum
head->burstT=head->burstT-quantum;
time=time+quantum;
cout <<"At "<<time<<" ,"<<="" head-="">nameProc<< " has been executing for "<<quantum<<" secs.="" it="" has="" "<<head-="">burstT<<" more."<<endl;
}
="" else="" {="" if(head-="">burstT>0) {time=time+head->burstT; // bt <= quantum deci se incheie
cout<<"At "<<time<<" ,"<<head-="">nameProc<<" has been executing for "<<head->burstT<<" secs. The process "<<head->nameProc<<" is finished."<<endl;
head-="">burstT=0;
deleteHead(head);
}}
}
int main()
{
int quantum,n,i,time=0; // time= current moment in time n=number of proc quantum= alocated execution time
struct process p[100];
cout<<"Give quantum: "; //read quantum
cin>>quantum;
while (quantum<1||quantum>10)
{
cout << "Quantum is not valid. Give a valid one: ";
cin >>quantum;
}
cout<<"Give number of proc:";
cin>>n;
for(i=0;i<n;i++)
{="" cout<<"add="" name,="" at,="" bt="" "<<i+1<<":="" ";="" arrival="" time="" &="" burst="" time
="" cin="">>p[i].nameProcess;
cin>>p[i].arrival_Time;
cin>>p[i].burst_Time;
p[i].inList=0; //no process is in the list yet
}
// I start working with the circular linked list
Nod*head=NULL;
Nod*tail=NULL;
do{
addArrivals(time,head,p,n);
exeProc(head,quantum,time);
}while(head!=NULL); ///??? condition for circular list ???
cout<<"At "<<time<<", all="" they="" are="" finished."<<endl;
return="" 0;
}如果有人能给我一些建议我会非常感激。
我尝试了什么：
我尝试了很多不同的方式来使用我已经制作的那些功能，但我似乎无法让它给出正确的输出顺序过程。输入：
名称到达burstTime with quantum = 3
P1 0 5
P2 1 3
P3 3 6
P4 5 1
P5 6 4
我收到订单：P1 P2 P1 P5 P3 P4 P3 P5
而不是：P1 P2 P3 P1 P4 P5 P3 P5
If anyone could give me some suggestions I'd deeply appreciate it.
What I have tried:
I tried so many different ways of using those functions I've made but I can't seem to get it to give the right output order of the processes. For the input:
name arrival burstTime with quantum=3
P1 0 5
P2 1 3
P3 3 6
P4 5 1
P5 6 4
I am getting the order: P1 P2 P1 P5 P3 P4 P3 P5
Instead of: P1 P2 P3 P1 P4 P5 P3 P5
推荐答案
算法很容易理解，但我似乎无法意识到我在代码中做错了什么：
The algorithm is easy to understand, but I can't seem to realize what am I doing wrong in my code:
你的代码行为不符合你的预期，或者你不明白为什么！
有一个几乎通用的解决方案：一步一步地在调试器上运行你的代码，检查变量。
调试器在这里向您展示您的代码正在做什么，您的任务是与它应该做什么进行比较。
调试器中没有魔法，它不知道你的cpde是什么应该这样做，它没有发现错误，它只是帮助你showi你知道发生了什么。当代码没有达到预期的效果时，你就接近了一个错误。
要查看你的代码在做什么：只需设置断点并查看代码是否正常运行，调试器允许你执行第1行第1行，并在执行时检查变量。
调试器 - 维基百科，免费的百科全书 [ ^ ]
掌握调试Visual Studio 2010 - 初学者指南 [ ^ ]
使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]
1.11 - 调试程序（步进和断点）|学习C ++ [ ^ ]
调试器仅显示您的代码正在执行的操作，您的任务是与应该执行的操作进行比较。
Your code do not behave the way you expect, or you don't understand why !
There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your cpde is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
1.11 — Debugging your program (stepping and breakpoints) | Learn C++[^]
The debugger is here to only show you what your code is doing and your task is to compare with what it should do.
一个评论很多，工作（至少看起来如此）的代码版本。
A heavily commented, working (at least it looks so) version of your code.
#include <iostream>
#include <string>
#include <vector>
using namespace std;
// Process
struct Proc
{
string name;
size_t arrival; // time of arrival
size_t exec; // toatal execution time
bool scheduled; // true if the process is inserted in the execution list
};
// show the Process
ostream & operator << ( ostream & os, const Proc & proc);
// Execution node
struct Node
{
const Proc * pproc; // pointer to the actual process
size_t remain; // remaining execution time
Node * next;
};
// Execution list
class ExecList
{
Node* head = nullptr;
size_t quantum = 3;
size_t time = 0; // current global execution time
public:
~ExecList();
void insert_nodes( vector <Proc> & vproc); // inserts suitable nodes
bool execute(); // executes current process ('head')
void remove(); // removes current process
void next(); // moves (head) to next process in the list
bool is_empty(); // true if there are no more processes in the list
void dump(); // shows the list (debugging)
};
void ExecList::next()
{
head = head->next;
}
bool ExecList::is_empty()
{
return (head == nullptr);
}
void ExecList::dump()
{
Node * cur = head;
if ( cur == nullptr) return;
do
{
cout << *(cur->pproc) << "\n";
cur = cur->next;
} while (cur != head);
}
void ExecList::insert_nodes( vector <Proc> & vproc )
{
// make a sublist with suitable nodes (for later insertion in the execution list)
Node * first = nullptr; // sublist first node
Node * last = nullptr; // sublist last node
for (auto & proc : vproc)
{
// add only not yet scheduled ones
if ( ! proc.scheduled && proc.arrival <= time )
{
Node * cur = new Node();
cur->pproc = &proc;
cur->remain = proc.exec;
proc.scheduled = true; // mark inserted process as 'scheduled'
cur->next = nullptr;
if ( first == nullptr )
{
first = cur;
last = cur;
}
else
{
last->next = cur;
last = cur;
}
}
}
// append the sublist at the end of the execution list
if ( first != nullptr )
{
if ( head == nullptr)
{
head = first;
last->next = head;
}
else
{
// find the last node of the execution list
Node * exec_last = head;
while ( exec_last->next != head)
exec_last = exec_last->next;
last->next = head;
exec_last->next = first;
}
}
}
ExecList::~ExecList()
{
// Release (if needed) allocated memory
Node * cur;
if ( ! head ) return;
cur = head;
do
{
Node * next = cur->next;
delete cur;
cur = next;
} while ( cur != head );
}
// executes the current porcess (head). Returns true if the process is finished and should be removed
bool ExecList::execute()
{
cout << "time " << time << ", executing process " << head->pproc->name << "\n";
size_t dt = min( quantum, head->remain);
head->remain -= dt;
time += dt;
return (head->remain == 0);
}
// removes the current process (head)
void ExecList::remove()
{
if ( ! head ) return;
if ( head->next == head )
{
delete head;
head = nullptr;
return;
}
Node * last = head->next;
while ( last->next != head )
last = last->next;
last->next = head->next;
delete head;
head = last->next;
}
ostream & operator << ( ostream & os, const Proc & proc)
{
os << "name " << proc.name << ", arrival " << proc.arrival << ", exec " << proc.exec << ", scheduled " << proc.scheduled;
return os;
}
istream & operator >> (istream & is, Proc & proc)
{
is >> proc.name >> proc.arrival >> proc.exec;
proc.scheduled = false;
return is;
}
int main()
{
size_t proc_count;
cout << "how many processes?\n";
cin >> proc_count;
vector <Proc> vproc;
for (size_t n=0; n < proc_count; ++n)
{
Proc proc;
cout << "enter process " << n << " name, arrival time, execution time\n";
cin >> proc;
vproc.push_back( proc );
}
ExecList el;
cout << "Execution:\n";
bool process_finished = false;
for (;;)
{
el.insert_nodes(vproc);
//el.dump(); // uncomment this line to see the process list at this step
if ( el.is_empty() ) break;
if ( process_finished )
{
el.remove();
if ( el.is_empty() ) break;
}
else
el.next();
process_finished = el.execute();
}
}
这篇关于为什么我的循环代码不能正常工作？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
