Multithreading variables do not update right...

[carlosrapa]

I am attempting this multithreading exercise and It is supposed to create 4 random numbers in the first thread then send them to Global Variables P_a, P_b, Q_a, Qb and then Thread 2 is supposed to calculate the midpoint, this process repeats until 10 sets of 4 are created, calculated and displayed... For somereason Thread one seems to only want to update my items once.. strangely though it will update them (except for P_a) if i debug in that area however the first figure stays the same... please help... I am a newbie obviously so dont be mad if I am just stupid ;) Thanks. OH I use /MT in the Commandline options.. and I am using .NET 2K3 C++


#include <process.h>
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
HANDLE hMutex;
float P_a;
float P_b;
float Q_a;
float Q_b;
unsigned Counter;
bool turn;
bool kill;

unsigned __stdcall SecondThreadFunc( void* pArguments )
{
float Midx;
float Midy;
DWORD dwWaitResult;
//printf( "Enter second thread...\n" );
while(1) {
// Request ownership of mutex.
dwWaitResult = WaitForSingleObject(hMutex, 5000L);
switch (dwWaitResult){
// The thread got mutex ownership.
case WAIT_OBJECT_0:
__try {
if (kill) {
printf( "Kill TRUE -- Thread Two Exiting -- Counter is-> %d\n", Counter );
_endthreadex( 0 );
return 0;
}
else {
if (turn == FALSE) {
///////////////Calulating////////////////////////////
Midx = ((P_a + Q_a)/2);
Midy = ((P_b + Q_b)/2);
///////////////////////////////////////////////////
printf( "MidPoint is -> (%.1f,%.1f)\n", Midx, Midy);
printf( "Thread Two Counter is-> %d\n", Counter );
Counter++;
turn = TRUE;
}
}
}
__finally {
// Release ownership of the mutex object.
if (! ReleaseMutex(hMutex)) {
printf( "if (! ReleaseMutex(hMutex)) in function\n");
// Deal with error.
}
break;
}
}
}
_endthreadex( 0 );
return 0;
}
int main()
{
HANDLE hThread;
unsigned threadID;
DWORD dwWaitResult;
int i;
bool endit = FALSE;
int random_integer;
int randomNumbers[4];
turn = TRUE;
Counter = 0; // initialize Counter
// Create a mutex with no initial owner.
hMutex = CreateMutex(NULL,FALSE,"MutexToProtectDatabase");
if (hMutex == NULL) {
// Check for error.
printf( "Error Creating MUTEX -- TERMINATING %d\n", Counter);
return 0;
}
///printf( "Creating second thread...\n" );
// Create the second thread.
hThread = (HANDLE) _beginthreadex( NULL, 0, &SecondThreadFunc, NULL, 0,&threadID);
while (1) {
//Request ownership of mutex.
dwWaitResult = WaitForSingleObject(hMutex, 5000L);
switch (dwWaitResult) {
// The thread got mutex ownership.
case WAIT_OBJECT_0:
__try
{
if (turn == TRUE){
/////////////////RANDOMIZER//////////////////
/* Seed the random-number generator with current time so that
* the numbers will be different every time we run.*/
srand( (unsigned)time( NULL ) );
/* Display 10 numbers. */
for( i = 0; i < 4 ;i++ ) {
random_integer = 1 + int(100 * rand()/(RAND_MAX+1.0));
randomNumbers[i] = random_integer;
printf( "Random Numer %3d\n", random_integer );
}
/////////////////////////////////////////////
P_a = randomNumbers[0];
P_b = randomNumbers[1];
Q_a = randomNumbers[2];
Q_b = randomNumbers[3];
Counter++;
printf( "Primary Thread Counter is-> %d\n", Counter);
turn = FALSE;
if (Counter > 19) {
kill = TRUE;
endit = TRUE;
break;
}
}
}
__finally
{
// Release ownership of the mutex object.
if (! ReleaseMutex(hMutex)) {
printf( "if (! ReleaseMutex(hMutex)) in main \n");
// Deal with error.
}
break;
}
}
if (endit) {
break;
}
}
WaitForSingleObject( hThread, INFINITE);
printf( "Counter should be 10; it is-> %d\n", Counter );
// Destroy the HANDLE object.
CloseHandle( hThread );
return 0;
}

[carlosrapa]

dont worry i figured it out i had to initialize the srand up higher in main...