Question

我现在正在研究Vertorization性能测试，但我遇到了以下错误

1＆gt; ConsoleApplication2.obj：错误LNK2001：未解析的外部符号“private：static union _LARGE_INTEGER Timer :: m_freq”（？m_freq @ Timer @@ 0T_LARGE_INTEGER @@ A） 1＆gt; ConsoleApplication2.obj：错误LNK2001：未解析的外部符号“private：static __int64 Timer :: m_overhead”（？m_overhead @ Timer @@ 0_JA） 1＆gt; c：\ users \ lara feodorovna \ documents \ visual studio 2012 \ Projects \ ConsoleApplication2 \ Debug \ ConsoleApplication2.exe：致命错误LNK1120：2个未解析的外部

--------------- timer.h（我手工添加）---------------

#pragma once
#include <windows.h>

struct Timer
{
     void Start() 
     {
         QueryPerformanceCounter(&m_start);
     }

     void Stop() 
     {
         QueryPerformanceCounter(&m_stop);
     }

     // Returns elapsed time in milliseconds (ms)
     double Elapsed()
     {
         return (m_stop.QuadPart - m_start.QuadPart - m_overhead) \
                                           * 1000.0 / m_freq.QuadPart;
     }

 private:

     // Returns the overhead of the timer in ticks
     static LONGLONG GetOverhead()
     {
         Timer t;
         t.Start();
         t.Stop();
         return t.m_stop.QuadPart - t.m_start.QuadPart;
     }

     LARGE_INTEGER m_start;
     LARGE_INTEGER m_stop;
     static LARGE_INTEGER m_freq;
     static LONGLONG m_overhead;
};

--------------------- ConsolApplication2.cpp -----------------------

#include "stdafx.h"
#include "timer.h"

const int MAXNUM = 100000;

int a[MAXNUM];
int b[MAXNUM];
int c[MAXNUM];

int _tmain(int argc, _TCHAR* argv[])
{
    Timer timer;
    double time_NoVector;
    double time_Vector;

    //No Vectorization
    timer.Start();
    #pragma loop(no_vector)
    for (int j=0; j<MAXNUM; j++)
    {
        c[j]=a[j]+b[j];
    }
    timer.Stop();
    time_NoVector=timer.Elapsed();

    //Vectorization
    timer.Start();
    for(int j=0; j <MAXNUM; j++)
    {
        c[j] = a[j] + b[j];
    }
    timer.Stop();
    time_Vector=timer.Elapsed();

    printf("---------------------------------------------\n");
    printf("%-14s %10s %10s\n", "Version", "Times(s)", "Speedup");
    printf("---------------------------------------------\n");
    printf("%-14s %10.4f %10.4f\n", "NoVector", time_NoVector, 1.0);
    printf("%-14s %10.4f %10.4f\n\n", "Vector", time_Vector, time_NoVector / time_Vector);

    return 0;

}

请帮帮我

Answer 1

struct Timer
{
.....
     static LARGE_INTEGER m_freq;  // This only declares a static member not definition
     static LONGLONG m_overhead;
};

您需要在.cpp文件中定义以下Timer的静态成员：

LARGE_INTEGER Timer::m_freq;
LONGLONG Timer::m_overhead;

Answer 2

如果static中有class个成员，则必须在翻译单元中对其进行定义。

在标题中：

struct Timer
{
    // ...

    // Declaration of your static members
    static LARGE_INTEGER m_freq;
    static LONGLONG m_overhead;
};

在.cpp中：

// Definitions
LARGE_INTEGER Timer::m_freq;
LONGLONG Timer::m_overhead;

尊重One Definition Rule。

Answer 3

对于那些学习这门课程的外行人来说，让我这样说吧。您将m_freq和m_overhead声明为静态，这意味着在包含timer.h的实现文件（.cpp）中的某个位置，您需要将这些成员的值定义为@billz提到的。 @Pierre Fourgeaud提到的翻译单元包含一个cpp文件及其包含的标题。示例初始化将是

在main.cpp中：

...
int b[MAXNUM];
int c[MAXNUM];

LARGE_INTEGER m_freq = {0};  // Define them outside of all functions
LONGLONG m_overhead = {0};

int _tmain(int argc, _TCHAR* argv[])
{
    ...
    return 0;
}

这会让你通过你看到的两个错误。

VS 2012错误LNK2001：未解析的外部符号

3 个答案: