/////////////////////////////////////////////////////////////////////
//  race.cpp  - demonstrate race condition                         //
//                                                                 //
//  Two threads attempt to run to completion, but second one       //
//  often blocks, waiting for output to finish, so only first      //
//  finishes.                                                      //
//  Jim Fawcett, CSE691 - Software Modeling & Analysis, Fall 2000  //
/////////////////////////////////////////////////////////////////////

#include <windows.h>
#include <process.h>
#include <iostream>
using namespace std;
//
// A race condition occurs when the fundamental behavior of
// your processing depends on the relative speed with which 
// individual threads do their work.  
//
// In this program one worker thread does all computation (simply 
// incrementing an integer), while another worker thread does the
// same, but also sends the result to standard output, a slow 
// process.
//
// The main thread (which created the two workers) only waits for
// the first to finish, then terminates, which also kills the
// remaining thread, which still has more work to do.  Thus
// thread 2 always loses the race, and never finishes.  In fact
// it generates an incorrect result, claiming that it did zero
// iterations, because it never got to update its iteration count
// at the end.
//
//----< thread processing function >---------------------------

unsigned int __stdcall threadProc1(void *pData) {

  int i, count=0;
  for(i=0; i<1000; i++)
    ++count;
  *((int*)pData) = count;
  return 0;
}

//----< thread processing function >---------------------------

unsigned int __stdcall threadProc2(void *pData) {

  int i, count=0;
  for(i=0; i<1000; i++) {
    ++count;

    // this output statement slows down the loop
    // causing a race condition
    
    cout << "\n  thread #2's count = " << count; 
    cout.flush();
  }
  // due to race condition in this program
  // this statement will never be executed

  *((int*)pData) = count;
  return 0;
}
//

//----< entry point for process >------------------------------

void main() {
  
  cout << "\n Demonstrate the Operation of Mult-threaded Code "
       << "\n With Race Condition"
       << "\n=======================================================\n\n";
    
// define an array of handles to threads, needed to wait
// for their completion

  const int NumHandles = 2;
  HANDLE thHand[NumHandles];

  int count1 = 0, count2 = 0;

// define argument values for thread #1 _beginthreadex

  string shared;
  void* Security = NULL;              // no security attributes
  unsigned int StackSize = 0;         // stack size picked by OS
  unsigned int(__stdcall threadProc1)(void*);  
                                      // name of thread function
  unsigned int InitFlag = 0;          // start running
  unsigned int ThreadID[2];           // receives thread id
  void *Arg1 = &count1;                // pointer to argument

// start first thread
  
  thHand[0] = 
    (HANDLE)_beginthreadex(
       Security, StackSize, threadProc1, Arg1, InitFlag, &ThreadID[0]
     );

//

// define argument values for thread #2 _beginthreadex

  void *Arg2 = &count2;

// start second thread

  thHand[1] = 
    (HANDLE)_beginthreadex(
      Security, StackSize, threadProc2, Arg2, InitFlag, &ThreadID[1]
    );

// tell process to wait for both threads to complete
// before terminating

  BOOL fwait = FALSE;                 // wait for first unsignaled handle
  DWORD timeOut = INFINITE;           // time out in milliseconds
  WaitForMultipleObjects(NumHandles, thHand, fwait, timeOut);
  
  CloseHandle(thHand[0]);             // return resources
  CloseHandle(thHand[1]);             // return resources

  Sleep(5);

  cout << "\n  count1 = " << count1
       << "\n  count2 = " << count2
       << "\n\n";
}