“英特尔杯”全国计算机多核程序设计大赛源码 第一题成绩0.109秒 供大家讨论

文件名: answer1_C_Map_0.109.cpp

说明: 使用文件内存映射,在后台用线程读取文件
利用变量 float fDiv; 减少乘法的次数

源码:

/*////////////////////////////////////////
// 版权所有(C) 2000-2008 邓辉 //
// Email： denghui0815@hotmail.com //
// 文件名： answer1.cpp //
// 说明： Intel优化大赛参赛作品 //
////////////////////////////////////////*/
#include <mathimf.h>
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <time.h>
#include <tmmintrin.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <process.h>

#define X_MIN_FLAT -3.402823466e+38F
#ifdef TEST_TIME
__int64 g_xFrequency;

void InitFrequency(void)
{
QueryPerformanceFrequency( (LARGE_INTEGER *)&g_xFrequency );
}

__int64 XGetTickCount(void)
{
__int64 nTick = -1;
QueryPerformanceCounter( (LARGE_INTEGER *)&nTick );
nTick = (__int64)(1000000 * (double)(nTick) / (double)(g_xFrequency));
return nTick;
}
#endif

int main(int argc, char *argv[])
{
#ifdef TEST_TIME
InitFrequency();

__int64 start = XGetTickCount();
#endif
struct stat buf ={0};

char szInput[MAX_PATH] = "r:\\test.dat";

if(argc > 1) strcpy(szInput, argv[1]);

HANDLE hProcess = GetCurrentProcess();

SetPriorityClass(hProcess, REALTIME_PRIORITY_CLASS);

if(stat(szInput, &buf))
{
printf("The file does not exist\n");
exit(0);
}

int nNum = buf.st_size/sizeof(float);

if(nNum < 4)
{
printf("乘积=%f 首数的序号=%d\n", 0, 0);
}
else
{
HANDLE hFile,hFileMappingIn;

hFile = CreateFile(szInput,
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_FLAG_SEQUENTIAL_SCAN,
NULL);

if(hFile == INVALID_HANDLE_VALUE)
{
printf("The file does not exist\n");
exit(0);
}

hFileMappingIn = CreateFileMapping(hFile,NULL,PAGE_READONLY, 0, 0, NULL);

CloseHandle(hFile);

int i=0,nIndex=0;
float fProduct = X_MIN_FLAT,fMin = X_MIN_FLAT,fMul,fTmp[3];
float* pArray = (float*)MapViewOfFile(hFileMappingIn, FILE_MAP_READ, 0, 0, NULL);
float fDiv = 1.0/10000.0/10000.0/10000.0;
i = 0;nNum-=3;

while(i < nNum)
{
if(pArray[i+3] < fMin)
{
i += 4;
}
else
{
fMul = pArray[i] * pArray[i+1] * pArray[i+2] * pArray[i+3];
if(fProduct < fMul)
{
fProduct = fMul;
fMin = fProduct*fDiv;
nIndex = i;
}
++i;
}
}

UnmapViewOfFile(pArray);

#ifdef TEST_TIME
printf("乘积=%f 首数的序号=%d 时间=%10.9f\n", fProduct, nIndex, (double)(XGetTickCount() - start) / 1000000);
#else
printf("乘积=%f 首数的序号=%d\n", fProduct, nIndex);
#endif
}
}