added b7 code

Codes/Group B/Assignment - 7/Page Replacement Algorithm - LRU, Optimal.cpp

@@ -0,0 +1,136 @@
+#include<iostream>
+using namespace std;
+
+int refstring[] = {0, 2, 1, 6, 4, 0, 1, 0, 3, 1, 2, 1};
+int win, hit = 0, miss = 0, res[4], lastUsed[40];
+
+int findLRU() {
+    int minIndex = 0;
+    for(int i = 1; i < win; i++){
+        if(lastUsed[i] < lastUsed[minIndex]){
+            minIndex = i;
+        }
+    }
+    return minIndex;
+}
+
+void lru(int rf[], int len)
+{
+    for(int i = 0; i < win; i++) {
+        res[i] = -1;
+        lastUsed[i] = -1;
+    }
+
+    for(int j = 0; j < len; j++) {
+        bool hitFlag = false;
+        for(int k = 0; k < win; k++){
+            if (res[k] == rf[j]){
+                hit++;
+                lastUsed[k] = j;
+                hitFlag = true;
+                break;
+            }
+        }
+        if (!hitFlag) {
+            miss++;
+            bool emptyFound = false;
+            for(int k = 0; k < win; k++){
+                if (res[k] == -1){
+                    res[k] = rf[j];
+                    lastUsed[k] = j;
+                    emptyFound = true;
+                    break;
+                }
+            }
+            if(!emptyFound){
+                int lruIndex = findLRU();
+                res[lruIndex] = rf[j];
+                lastUsed[lruIndex] = j;
+            }
+        }
+    }
+
+    cout<<"\nNo of hits (LRU): "<<hit;
+    cout<<"\nNo of misses (LRU): "<<miss;
+}
+
+int findOptimal(int rf[], int len, int currentIndex)
+{
+    int maxIndex = -1, farthest = currentIndex;
+    for(int i = 0; i < win; i++){
+        int j;
+        for(j = currentIndex + 1; j < len; j++){
+            if(res[i] == rf[j]){
+                if(j > farthest){
+                    farthest = j;
+                    maxIndex = i;
+                }
+                break;
+            }
+        }
+        if(j == len)
+            return i;
+    }
+    return maxIndex;
+}
+
+void optimal(int rf[], int len){
+    hit = 0;
+    miss = 0;
+
+    for(int i = 0; i < win; i++){
+        res[i] = -1;
+    }
+
+    for(int j = 0; j < len; j++){
+        bool hitFlag = false;
+        for(int k = 0; k < win; k++){
+            if (res[k] == rf[j]){
+                hit++;
+                hitFlag = true;
+                break;
+            }
+        }
+        if (!hitFlag){
+            miss++;
+            bool emptyFound = false;
+            for(int k = 0; k < win; k++){
+                if (res[k] == -1){
+                    res[k] = rf[j];
+                    emptyFound = true;
+                    break;
+                }
+            }
+            if(!emptyFound){
+                int optimalIndex = findOptimal(rf, len, j);
+                res[optimalIndex] = rf[j];
+            }
+        }
+    }
+
+    cout<<"\nNo of hits (Optimal): "<<hit;
+    cout<<"\nNo of misses (Optimal): "<<miss;
+}
+
+void display()
+{
+    cout<<"\nPages in window are: \n";
+    for(int i = 0; i < win; i++){
+        cout<<res[i]<<"\n";
+    }
+}
+
+int main()
+{
+    cout<<"\nEnter window size: ";
+    cin>>win;
+    int len = sizeof(refstring)/sizeof(refstring[0]);
+
+    cout<<"\nBy LRU algorithm: ";
+    lru(refstring, len);
+    display();
+
+    cout<<"\n\nBy Optimal Algorithm: ";
+    optimal(refstring, len);
+    display();
+}