www.pudn.com > BUSY2-pwj.rar > BUSY2.C

/* 
 * Busy2.c 
 * 
 * Sample code for Multithreading Applications in Win32 
 * This sample is mentioned in the text but there is 
 * no associated listing in the book. 
 * 
 * Run a busy loop and a worker thread at 
 * the same time. This program is intended 
 * to be monitored by PerfMon in Windows NT. 
 * You will need to Ctrl-C out to exit. 
 * 
 * Build command: cl /MD busywait.c 
 */ 
 
#define WIN32_LEAN_AND_MEAN 
#include  
#include  
#include  
#include  
#include "MtVerify.h" 
 
DWORD WINAPI ThreadFunc(LPVOID); 
 
int main() 
{ 
    HANDLE hThrd; 
    DWORD exitCode = 0; 
    DWORD threadId; 
    DWORD begin; 
    DWORD elapsed; 
 
    puts("Busy2 is designed to use up CPU time."); 
    puts("Press Ctrl+C to exit."); 
    begin = GetTickCount(); 
 
    MTVERIFY( hThrd = CreateThread(NULL, 
        0, 
        ThreadFunc, 
        (LPVOID)1, 
        0, 
        &threadId ) 
    ); 
    /* This busy loop chews up lots of CPU time */ 
    for (;;) 
    { 
        GetExitCodeThread(hThrd, &exitCode); 
        if ( exitCode != STILL_ACTIVE ) 
            break; 
    } 
 
    elapsed = GetTickCount()-begin; 
    printf("Thread + busy loop took: %d.%.03d seconds\n", 
                elapsed/1000, elapsed%1000); 
 
    MTVERIFY( CloseHandle(hThrd) ); 
 
    return EXIT_SUCCESS; 
} 
 
 
/* 
 * Cute little busy work routine that computes the value 
 * of PI using probability.  Highly dependent on having 
 * a good random number generator (rand is iffy) 
 */ 
DWORD WINAPI ThreadFunc(LPVOID n) 
{ 
    int i; 
    int inside = 0; 
    double val; 
 
    UNREFERENCED_PARAMETER(n); 
 
    /* Seed the random-number generator */ 
    srand( (unsigned)time( NULL ) ); 
 
    for (i=0; i<100000000; i++) 
    { 
        double x = (double)(rand())/RAND_MAX; 
        double y = (double)(rand())/RAND_MAX; 
        if ( (x*x + y*y) <= 1.0 ) 
            inside++; 
    } 
    val = (double)inside / i; 
    printf("PI = %.4g\n", val*4); 
    return 0; 
}