我正在使用C ++开发一个离散事件模拟程序。我的输出完全不正确，但所有输出值都非常接近正确的输出。我试过调试我的算法，但我找不到任何错误。下面是我的主要算法算法。
我使用最小堆和数组实现了事件优先级队列。我不允许使用任何STL库。代码中使用的FIFO队列是链表。当我在优先级队列的顶部打印事件时间时，事件并不总是以升序传递（我认为事件优先级队列应该如何工作），我不明白为什么。升序主要在事件完成时间附近被破坏。请帮忙！
#include <iostream>
#include <fstream>
#include "PQueue.h"
#include "SPqueue.h"
#include "LinkedList.h"
using namespace std;
int serverCount; //number of servers
Spqueue spq; //priority queue for servers
Pqueue pq; //priority queue for events
LinkedList list; //FIFO queue to put arriving events in
double totalTime; //variables for statistics calculation
double timeNow;
double totalWait;
int ql;
int qlength = 0;
double totalQlength;
int time = 0;
bool available(); //checks availability of servers
int main() {
ifstream fin;
fin.open("Sample2.txt");
if (!fin.good())
cerr << "Couldn't find file/corrupted file" << endl;
fin >> serverCount; //reads number of servers and efficiency
//from file
for (int i = 0; i < serverCount; i++) {
server s;
fin >> s.effi;
s.status = true;
s.count = 0;
spq.insert(s);
}
//reads first event from file
event e;
fin >> e.eventTime;
fin >> e.serviceTime;
e.eventType = -1;
pq.insert(e);
int i = 1;
//while priority queue is not empty
while (!pq.isEmpty()) {
timeNow = pq.getArrivalTime(1);
while (time < pq.getArrivalTime(1)) {
totalQlength = totalQlength + list.getLength();
time++;
}
//get event from priority queue
if (pq.getServer(1) == -1) { //if arrival event, add to FIFO queue
list.AddTail(pq.getArrivalTime(1), pq.getServiceTime());
if (list.getLength() > qlength) {
qlength = list.getLength();
}
//read next arrival event from file
if (!fin.eof()) {
event e;
fin >> e.eventTime;
fin >> e.serviceTime;
e.eventType = -1;
pq.insert(e);
i++;
}
}
else //must be customer complete event
{
spq.setIdle(pq.getServer(1)); //set the server to idle
}
pq.deleteMin(); //remove the evnt from priority queue
//if FIFO queue is not empty and servers are available
//process event
if ((list.isEmpty() == false) && (available() == true)) {
list.getHead();
int s = spq.getMin();
spq.setBusy(s); //set server to busy
spq.incrementCustNumber(s); //increment number of customers
//served
double waitTime = timeNow - list.getHead().arrivalTime;
totalWait = totalWait + waitTime;
double serviceT = spq.getEffi(s) * list.getHead().serviceTime;
double eventT = list.getHead().arrivalTime +serviceT;
event e2;
e2.eventTime = eventT;
e2.serviceTime = list.getHead().serviceTime;
e2.eventType = s;
pq.insert(e2); //add customer complete event to the priority
//queue
list.RemoveHead(); //remove head from FIFO
}
totalTime = pq.getArrivalTime(1);
}
fin.close();
return 0;
}
bool available() {
bool ava = false;
for (int i = 1; i <= serverCount; i++) {
if (spq.getStatus(i) == true) {
ava = true;
break;
}
}
return ava;
}
以下是优先级队列实现：
#include <iostream>
#include <fstream>
#include "PQueue.h"
using namespace std;
Pqueue::Pqueue() {
inde = 0; //length of heap
}
void Pqueue::insert(event i) { //inserts new element into the heap array and maintains min heap property
inde++;
pqueue[inde] = i;
siftup(inde);
}
int Pqueue::getServer(int i) {
return pqueue[i].eventType;
}
void Pqueue::siftup(int i) { //shifts element up to the correct position in the heap
if (i == 1)
return;
int p = i / 2;
if (pqueue[p].eventTime > pqueue[i].eventTime)
{
swap(pqueue[i], pqueue[p]);
siftup(p);
}
}
void Pqueue::deleteMin() { //removes element at the root of the heap
swap(pqueue[inde], pqueue[1]);
inde--;
siftdown(1);
}
void Pqueue::siftdown(int i) { //shifts element to its position in the min heap
int c = i * 2;
int c2 = (i * 2) + 1;
if (c > inde) return;
int in = i;
if (pqueue[i].eventTime > pqueue[c].eventTime)
{
in = c;
}
if ((c2 < inde) && (pqueue[i].eventTime > pqueue[c2].eventTime))
{
in = c2;
}
if (pqueue[c].eventTime < pqueue[c2].eventTime) {
in = c;
}
if (in != i) {
swap(pqueue[i], pqueue[in]);
siftdown(in);
}
}
void Pqueue::swap(event& i, event& j) {
event temp;
temp = i;
i = j;
j = temp;
}
bool Pqueue::isEmpty() { //checks if the priority queue is empty
if (inde == 0) return true;
else
return false;
}
double Pqueue::getArrivalTime(int i) {
return pqueue[i].eventTime;
}
double Pqueue::getServiceTime() {
return pqueue[1].serviceTime;
}
有五台服务器效率不同。将使用最有效的空闲服务器。为此，我在开始时对服务器阵列进行了有效的排序。
#include <iostream>
#include <fstream>
#include "SPqueue.h"
using namespace std;
Spqueue::Spqueue() {
inde = 0;
}
void Spqueue::insert(server i) { //inserts new element into the array
inde++;
spqueue[inde] = i;
}
void Spqueue::heapify(int n, int i)
{
int largest = i; // Initialize largest as root
int l = 2 * i; // left = 2*i + 1
int r = 2 * i +1; // right = 2*i + 2
// If left child is larger than root
if (l < n && spqueue[l].effi > spqueue[largest].effi)
largest = l;
// If right child is larger than largest so far
if (r < n && spqueue[r].effi > spqueue[largest].effi)
largest = r;
// If largest is not root
if (largest != i)
{
swap(spqueue[i], spqueue[largest]);
// Recursively heapify the affected sub-tree
heapify(n, largest);
}
}
void Spqueue::heapSort()
{
// Build heap (rearrange array)
for (int i = inde / 2 - 1; i > 0; i--)
heapify(inde, i);
// One by one extract an element from heap
for (int i = inde - 1; i > 0; i--)
{
// Move current root to end
swap(spqueue[1], spqueue[i]);
// call max heapify on the reduced heap
heapify(i, 1);
}
}
void Spqueue::swap(server& i, server& j) {
server temp;
temp = i;
i = j;
j = temp;
}
int Spqueue::getMin() { //iterates to the next available server in the sorted list of servers
int i = 0;
while (i <=20){
if (spqueue[i].status == true)
{
return i;
}
else
{
i++;
}
}
}
bool Spqueue::getStatus(int i) {
return spqueue[i].status;
}
void Spqueue::setBusy(int i) {
spqueue[i].status = false;
}
void Spqueue::addServiceTime(int i,double s) {
spqueue[i].busyTime = spqueue[i].busyTime + s;
}
double Spqueue::getTotalServiceTime(int i) {
return spqueue[i].busyTime;
}
void Spqueue::setIdle(int i) {
spqueue[i].status = true;
}
double Spqueue::getEffi(int i) {
return spqueue[i].effi;
}
void Spqueue::incrementCustNumber(int i) {
spqueue[i].count++;
}
int Spqueue::getCount(int i) {
return spqueue[i].count;
}
以下函数应该返回最有效的服务器。
int Spqueue::getMin() { //iterates to the next available server in
the already sorted array
int i = 0;
while (i <=20){
if (spqueue[i].status == true)
{
return i;
}
else
{
i++;
}
}
}
答案 0 :(得分：0)
siftdown的优先级队列实施存在一些问题。
void Pqueue::siftdown(int i) { //shifts element to its position in the min heap
int c = i * 2;
int c2 = (i * 2) + 1;
// *** Possible bug
// *** I think that if c == inde, then c is indexing beyond the current queue
if (c > inde) return;
int in = i;
if (pqueue[i].eventTime > pqueue[c].eventTime)
{
in = c;
}
if ((c2 < inde) && (pqueue[i].eventTime > pqueue[c2].eventTime))
{
in = c2;
}
// ***************
// ** Bug here
if (pqueue[c].eventTime < pqueue[c2].eventTime) {
in = c;
}
if (in != i) {
swap(pqueue[i], pqueue[in]);
siftdown(in);
}
}
首先，我想你要测试c1 >= inde。此外，当您检查是否pqueue[c].eventTime < pqueue[c2].eventTime时，如果不确定c2是否在范围内，则会这样做。
我发现以下内容是一种更清晰简洁的做法：
// find the smallest child
int in = c;
if (c2 < inde && pqueue[c2] < pqueue[c])
{
in = c2;
}
if (pqueue[in] < pqueue[i]) {
swap(pqueue[i], pqueue[in]);
siftdown(in);
}