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pagerep.c
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pagerep.c
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/*============================================================================*
pagerep.c
This program compares the performance of different page replacement
algorithms.
A makefile is provided, use the 'make' command to compile
Author: Ben Pogrund
*============================================================================*/
/* libraries */
#include <stdio.h>
#include <colorlogs.h> // Added for readability
/* macros */
#define PAGE_COUNT 5
/* user input handling */
void get_input(char* refstr);
int valid_input(char input);
void print_str(char* refstr);
void print_hits(int* hits, int length);
/* page replacement algorithms */
int paging_test(const char* refstr, int frameCount,
int (*swap_heuristic)(const char*, int*, int, int));
int optimal_swap(const char* refstr, int* frames, int frameCount,
int startPosition);
int lru_swap(const char* refstr, int* frames, int frameCount,
int startPosition);
/* helper functions */
int getlength(const char* refstr);
int _atoi(char input); // copies out a single digit, and converts it to int
/*===========================================================================*/
int main () {
char refstr[31]; // 30 characters + null terminator
int frameCount = 0; // input from user
int fault_count = 0; // fault counts from paging tests
// Input handling
printf ("\n");
LOG_GOLD ("#------------------------------------------------------#\n\n");
LOG_WHITE("Enter up to 30 page indices [0 - 5]\n");
LOG_GREEN(" > ");
get_input(refstr);
printf ("\n");
LOG_CYAN ("Ref String (%d entries):\n", getlength(refstr));
printf (" ");
print_str(refstr);
printf ("\n");
LOG_WHITE("Enter number of frames:\n");
LOG_GREEN(" > ");
scanf ("%d", &frameCount); // Not safe with invalid input
printf ("\n");
// Algorithm tests
LOG_CYAN ("Test results:\n");
LOG_WHITE(" Optimal Algorithm:\n");
fault_count = paging_test(refstr, frameCount, optimal_swap);
printf(" [ %d faults ]\n\n", fault_count);
LOG_WHITE(" LRU Algorithm:\n");
fault_count = paging_test(refstr, frameCount, lru_swap);
printf(" [ %d faults ]\n\n", fault_count);
LOG_GOLD ("#------------------------------------------------------#\n\n");
return 0;
}
void get_input(char* refstr) {
int i = 0;
char input;
while ((input = getchar()) != '\n' || i == 0) {
if (valid_input(input)) {
refstr[i++] = input;
if (i == 30) {
refstr[31] = '\0';
while ((input = getchar()) != '\n')
/* eat through remaining input */
;
return;
}
}
}
refstr[i] = '\0';
}
int valid_input(char input) {
return (atoi(&input) > 0 && atoi(&input) < PAGE_COUNT + 1);
}
void print_str(char* refstr) {
int i = 0;
while (refstr[i+1] != '\0') {
printf("%c, ", refstr[i++]);
}
printf("%c\n", refstr[i]);
}
void print_hits(int* hits, int length) {
int i = 0;
for (i = 0; i < length-1; i++) {
(hits[i]) ? LOG_GREEN("o ") : LOG_CRIM("x ");
}
(hits[i]) ? LOG_GREEN("o\n") : LOG_CRIM("x\n");
}
/*===========================================================================*/
int paging_test(const char* refstr, int frameCount,
int (*swap_heuristic)(const char*, int*, int, int))
{
int fault_count = 0;
int frames[frameCount];
int hits[getlength(refstr)];
// initialize page indices in frame set
int i;
for (i = 0; i < frameCount; i++)
frames[i] = 0;
// Paging process
int j = 0; i = 0;
while (refstr[i] != '\0') {
int frame_id = -1;
int open_id = -1;
int swap_id;
// Look up page in frame table
for (j = 0; j < frameCount; j++) {
if (frames[j] == _atoi(refstr[i])) {
frame_id = j;
break;
} else if (frames[j] == 0) {
open_id = j;
}
}
if (frame_id == -1) {
// Page miss
fault_count++;
hits[i] = 0;
if (open_id != -1) {
// Insert to open frame
frames[open_id] = _atoi(refstr[i]);
} else {
// Swap due to no open frames
swap_id = swap_heuristic(refstr, frames, frameCount, i);
frames[swap_id] = _atoi(refstr[i]);
}
} else {
// Page hit
hits[i] = 1;
}
/* ---- for debugging ----- */
/**
int k;
printf("<");
for (k = 0; k < frameCount; k++) printf ("%d", frames[k]);
printf(">\n");
**/
i++;
}
printf(" "); print_str(refstr);
printf(" "); print_hits(hits, getlength(refstr));
printf("\n");
return fault_count;
}
int optimal_swap(const char* refstr, int* frames, int frameCount,
int startPosition)
{
int next_use[PAGE_COUNT+1];
int pendingCount = frameCount-1;
int i;
// Initialize next_use (1 means usable, 0 means not)
for (i = 1; i <= PAGE_COUNT; i++) {
next_use[i] = 0;
}
// Enable entries that are in frame set (in main memory)
for (i = 0; i < frameCount; i++) {
next_use[frames[i]] = 1;
}
// This method looks into the future
i = startPosition+1;
while (i < getlength(refstr) && pendingCount) {
if (next_use[_atoi(refstr[i])] == 1) {
next_use[_atoi(refstr[i])] = 0;
pendingCount--;
}
i++;
}
// Find a good index
for (i = 1; i <= PAGE_COUNT; i++) {
if (next_use[i] == 1) {
int k;
for (k = 0; k < frameCount; k ++) {
if (frames[k] == i) return k;
}
}
}
fprintf(stdout, "Optimal swap error");
return -1;
}
int lru_swap(const char* refstr, int* frames, int frameCount,
int startPosition)
{
int last_use[PAGE_COUNT+1];
int pendingCount = frameCount-1;
int i;
// Initialize last_use (1 means usable, 0 means not)
for (i = 1; i <= PAGE_COUNT; i++) {
last_use[i] = 0;
}
// Enable entries that are in frame set (in main memory)
for (i = 0; i < frameCount; i++) {
last_use[frames[i]] = 1;
}
// This method looks into the future
i = startPosition-1;
while (i >= 0 && pendingCount) {
if (last_use[_atoi(refstr[i])] == 1) {
last_use[_atoi(refstr[i])] = 0;
pendingCount--;
}
i--;
}
// Find a good index
for (i = 1; i <= PAGE_COUNT; i++) {
if (last_use[i] == 1) {
int k;
for (k = 0; k < frameCount; k ++) {
if (frames[k] == i) return k;
}
}
}
fprintf(stdout, "LRU swap error");
return -1;
}
/*===========================================================================*/
int getlength(const char* refstr) {
int i = 0;
while (refstr[i] != '\0') i++;
return i;
}
int _atoi(char input) {
// atoi for single digits, 0-9
return input-48;
}
/*===========================================================================*/