// Parallel.cpp : 定義控制臺應用程序的入口點。

//

#include "stdafx.h"

#include

#include

static long num_steps = 100000;

const int numThreads = 4;

double step, pi;

CRITICAL_SECTION g_cs;

double sum = 0.0;

DWORD WINAPI countFunc(LPVOID pArg) {

double x;

int i;

int temp = *(int *)pArg;

int start = (temp*num_steps) / 4;

int end = start + num_steps / 4;

for (i = start; i < end; i++) {

EnterCriticalSection(&g_cs);

x = (i + 0.5)*step;

sum = sum + 4.0 / (1.0 + x*x);

LeaveCriticalSection(&g_cs);

}

return 0;

}

void main()

{

int i;

HANDLE hThread[numThreads];

step = 1.0 / (double)num_steps;

int tNum[numThreads];

InitializeCriticalSection(&g_cs);

for (int i = 0; i < numThreads; i++) {

tNum[i] = i;

hThread[i] = CreateThread(NULL, 0, countFunc, (LPVOID)&tNum[i], 0, NULL);

}

WaitForMultipleObjects(numThreads, hThread, TRUE, INFINITE);

DeleteCriticalSection(&g_cs);

pi = step * sum;

printf("PI = %12.9f\n", pi);

system("pause");

}

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