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  1. #include <iostream>
  2. #include <thread>
  3. #include <chrono>
  4. #include <atomic>
  5.  
  6. using namespace std;
  7.  
  8. // Shared variables
  9. atomic<bool> flag0(false);  // Flag for process 0
  10. atomic<bool> flag1(false);  // Flag for process 1
  11. atomic<int> turn(0);        // Variable for turn-based coordination
  12.  
  13. void process(int id) {
  14.     int other = 1 - id;  // Determine the other process
  15.  
  16.     for (int i = 0; i < 3; ++i) {  // Run the process three times
  17.         // Request to enter critical section
  18.         if (id == 0) {
  19.             flag0 = true;  // Mark process 0 as requesting critical section
  20.             turn = 1;      // Give turn to process 1
  21.         } else {
  22.             flag1 = true;  // Mark process 1 as requesting critical section
  23.             turn = 0;      // Give turn to process 0
  24.         }
  25.  
  26.         // Wait until the other process exits critical section
  27.         while ((id == 0 && flag1 && turn == 1) || (id == 1 && flag0 && turn == 0)) {
  28.             // Busy wait (not ideal, but needed for mutual exclusion)
  29.         }
  30.  
  31.         // Critical Section
  32.         cout << "Process " << id << " is in critical section" << endl;
  33.         this_thread::sleep_for(chrono::seconds(1));  // Simulate work in the critical section
  34.  
  35.         // Exit critical section
  36.         if (id == 0) {
  37.             flag0 = false;  // Reset flag for process 0
  38.         } else {
  39.             flag1 = false;  // Reset flag for process 1
  40.         }
  41.  
  42.         cout << "Process " << id << " is in remainder section" << endl;
  43.         this_thread::sleep_for(chrono::milliseconds(500));  // Simulate work in the remainder section
  44.     }
  45. }
  46.  
  47. int main() {
  48.     // Create two threads representing two processes
  49.     thread t1(process, 0);
  50.     thread t2(process, 1);
  51.  
  52.     // Start both threads (they start automatically upon creation)
  53.     // Wait for threads to complete
  54.     t1.join();
  55.     t2.join();
  56.  
  57.     return 0;
  58. }
Success #stdin #stdout 2.99s 5292KB
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stdin
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Standard input is empty
stdout
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Process 1 is in critical section
Process 1 is in remainder section
Process 0 is in critical section
Process 0 is in remainder section
Process 1 is in critical section
Process 1 is in remainder section
Process 0 is in critical section
Process 0 is in remainder section
Process 1 is in critical section
Process 1 is in remainder section
Process 0 is in critical section
Process 0 is in remainder section
https://ideone.com/5am8Ta
language:
C++ (gcc 8.3)
created:
12 days ago
visibility:
public

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