最差拟合算法

Question

我创建了一个代码，它使用大小为 256 的数组来演示 First Fit 算法，该代码显示了一个地图，显示了如何根据 First Fit 算法存储内存，该代码允许用户删除内存位置也是，我想创建与我的代码相同的概念，但使用最差拟合算法，我已经阅读了很多文章并理解了最差拟合算法的工作原理，但我想不出一种方法让我的代码使用Worst Fit Algorithm ，在我的代码上使用 First Fit 比 Worst Fit 更容易，有人可以告诉我如何实现我的代码以使用 Worst Fit Algorithm ，将不胜感激。

这是代码：

include <iostream>
#include <cmath>

using namespace std;

int PutInMemory(int memory[], int size) {

if (size < 1) cout << "Error!" << endl;
int firstSize = 0;
int j;
for (int i = 0; i < 256; i++) {
    if (memory[i] < 0 && abs(memory[i]) >= size) {
        j = i;
        firstSize += abs(memory[j]);
        break;
    }
}
if (firstSize < size) {
    cout << "Out of Memory";
    return 0;
}
if (j + size <= 256) {
    memory[j] = size;
    for (int i = j + 1; i < j + size; i++)
        memory[i] = 0;
    int i = j + size;
    int count = 0;
    while (memory[i] <= -1 && i < 256) {
        count++;
        i++;
    }
    if (count != 0) {
        memory[i - 1] = -count;
        memory[j + size] = -count;
    }
    return j;

}
else {
    cout << "Out of memory";
}

}


void DelSeg(int memory[], int n) {
int count = memory[n];
int prev = 0;
int next = count - 1;
int i = n + 1;
int pos = n;
if (memory[n - 1] < -1 && n != 0) {
    i += memory[n - 1];
    prev = -memory[n - 1];
    count -= memory[n - 1];
    pos = i;
}
while (true) {
    for (i; i < pos + count - 1; i++) {
        memory[i] = -1;
    }
    if (memory[i + 1] < -1) {
        count += -memory[i + 1] + 1;
        next = -memory[i + 1];
    }
    else {
        break;
    }
}

memory[n - prev] = 0 - count;
memory[n + next] = 0 - count;
}

void checkMemory(int memory[]) {
int countFreeSeg = 0;
int countFullSeg = 0;
int countFullMem = 0;
int countFreeMem = 0;

for (int i = 0; i < 256; i++) {
    if (memory[i] < 0) {
        if (memory[i] < 0) cout << "Beginning of the adress:" << i << ", ";
        int count = 0;
        while (memory[i] < 0 && i < 256) {
            count++;
            i++;
        }
        countFreeSeg++;
        cout << "Size = " << count << endl;
        countFreeMem += count;
        i--;
    }
}
cout << "Number of free processes = " << countFreeSeg << endl << endl;
cout << "Number of free memory = " << countFreeMem << endl << endl;


for (int i = 0; i < 256; i++) {
    if (memory[i] > 0) {
        cout << "Beginning adress: " << i << ", size - " << memory[i] << endl;
        countFullMem += memory[i];
        i += memory[i] - 1;
        countFullSeg++;
    }
}
cout << "Number of occupied processes = " << countFullSeg << endl;
cout << "Number of occupied memory = " << countFullMem << endl;
}

void print(int memory[]) {
for (int i = 0; i < 256; i++) {
    cout << memory[i] << " ";
}
}


int main()
{
int memory[256];
memory[0] = -256;
for (int i = 1; i < 256; i++) {
    memory[i] = -1;
}

while (true) {
    system("cls");
    cout << "1.Allocate Memory \n2.Free memory segment\n3.Get information about the 
memory\n4.Exit" << endl;
    int choice;
    cin >> choice;
    int m = 0;

    switch (choice)
    {
    case 1:
        system("cls");
        cout << "Enter the amount of memory to be entered:" << endl;
        cin >> m;
        cout << PutInMemory(memory, m) << endl;
        break;
    case 2:
        system("cls");
        cout << "Enter the starting address of the memory location:" << endl;
        cin >> m;
        DelSeg(memory, m);
        break;
    case 3:
        checkMemory(memory);
        print(memory);
        break;
    case 4:
        system("cls");
        exit(0);
        break;
    default:
        cout << "Incorrect entry" << endl;
        break;
    }
    system("pause");
}
}

Answer 1

您的 FirstFit 代码通过查找第一个足够大的内存块来容纳您请求的分配来工作。找到合适的方块后立即停下来。

  int firstSize = 0;
  int j;
  for (int i = 0; i < 256; i++) {
    if (memory[i] < 0 && abs(memory[i]) >= size) {
      j = i;
      firstSize += abs(memory[j]);
      break;
    }
  }
  if (firstSize < size) {
    cout << "Out of Memory";
    return 0;
  }

对于 WorstFit，您只需找到最大的可用连续内存块并分配它（如果它足够大）。

  int worstSize = 0;
  int j;
  for (int i = 0; i < 256; i++) {
    if (memory[i] < 0 && abs(memory[i]) >= worstSize) {
      j = i;
      worstSize = abs(memory[j]);
    }
  }
  if (worstSize < size) {
    cout << "Out of Memory";
    return 0;
  }