Código:
/*
This simple code demonstrates CreateEvent, WaitForMultipleObjects
Win32 API functions and event objects.
This code computes sum of Mercator's series.
Mercator's series expression for ln( x + 1 ) function is:
ln( x + 1 ) = x - x^2/2 + x^3/3 - x^4/4 + x^5/5 - ...
for -1 < x <= 1.
*/
#include <stdio.h>
#include <conio.h>
#include <time.h>
#include <windows.h>
#include <math.h>
#define NUMTHREADS 4
#define SERIES_MEMBER_COUNT 20000
HANDLE *threadHandles, masterThreadHandle;
CRITICAL_SECTION countCS;
double *sums;
double x = 1.0, res = 0.0;
int threadCount = 0;
double getMember(int n, double x)
{
double numerator = 1;
for( int i=0; i<n; i++ )
numerator = numerator*x;
if ( n % 2 == 0 )
return ( - numerator / n );
else
return numerator/n;
}
DWORD WINAPI threadProc(LPVOID par)
{
int threadIndex = *((int *)par);
sums[threadIndex] = 0;
for(int i=threadIndex; i<SERIES_MEMBER_COUNT;i+=NUMTHREADS)
sums[threadIndex] += getMember(i+1, x);
//Signal Master thread that one more processing thread is done
EnterCriticalSection(&countCS);
threadCount++;
LeaveCriticalSection(&countCS);
delete par;
return 0;
}
DWORD WINAPI masterThreadProc(LPVOID par)
{
for( int i=0; i<NUMTHREADS; i++ ) ResumeThread(threadHandles[i]); // Start computing threads
while (threadCount != NUMTHREADS) {} // busy wait until all threads are done with computation of partial sums
res = 0;
for(int i=0; i<NUMTHREADS; i++)
res += sums[i];
return 0;
}
int main()
{
threadHandles = new HANDLE[NUMTHREADS + 1];
InitializeCriticalSection(&countCS);
sums = new double[NUMTHREADS];
clock_t start,stop;
start=clock();
for(int i=0; i<NUMTHREADS;i++)
{
int * threadIdPtr = new int;
*threadIdPtr = i;
threadHandles[i] = CreateThread(NULL, 0, threadProc, threadIdPtr, CREATE_SUSPENDED, NULL);
}
threadHandles[NUMTHREADS] = CreateThread(NULL, 0, masterThreadProc, NULL, 0, NULL);
printf("Count of ln(1 + x) Mercator's series members is %d\n",SERIES_MEMBER_COUNT);
printf("Argument value of x is %f\n", (double)x);
WaitForMultipleObjects(NUMTHREADS+1,threadHandles,TRUE,INFINITE);
stop=clock();
printf("Tiempo = %2.7f\n",(float)(stop - start)/ CLOCKS_PER_SEC);
for(int i=0; i<NUMTHREADS+1; i++ ) CloseHandle(threadHandles[i]);
delete threadHandles;
DeleteCriticalSection(&countCS);
delete sums;
printf("Result is %10.8f\n", res);
printf("By function call ln(1 + %f) = %10.8f\n",x, log(1+x));
printf("Press any key ... ");
getch();
return 0;
}
