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我正在执行过滤器代码。此代码在 Visual Studio 和代码块中给出不同的结果。预期结果是代码块给出的结果。但由于我必须在其中实现英特尔线程构建块，我必须使用 Visual Studio。请帮助找出为什么存在差异。

Code is :


#include <stdio.h>
#include <stdint.h>
#include <cstring>
#include <iostream>
#include <fstream>
#include <math.h>
#include  <time.h>
using namespace std;

#define pi 3.141593
#define FILTER_LEN  265

double coeffs[ FILTER_LEN ] =
{
  0.0033473431384214393,0.000032074683390218124,0.0033131082058404943,0.0024777666109278788,
  -0.0008968429179843104,-0.0031973449396977684,-0.003430943381749411,-0.0029796565504781646,
  -0.002770673157048994,-0.0022783059845596586,-0.0008531818129514857,0.001115432556294998,
  0.0026079871108133294,0.003012423848769931,0.002461420635709332,0.0014154004589753215,
  0.00025190669718400967,-0.0007608257014963959,-0.0013703600874774068,-0.0014133823230551277,
  -0.0009759556503342884,-0.00039687498737139273,-0.00007527524701314324,-0.00024181463305012626,
  -0.0008521761947454302,-0.00162618205097997,-0.002170446498273018,-0.002129903305507943,
  -0.001333859049002249,0.00010700092934983156,0.0018039564602637683,0.0032107930896349583,
  0.0038325849735515363,0.003416201274366522,0.002060848732332109,0.00017954815260431595,
  -0.0016358832300944531,-0.0028402136847527387,-0.0031256650498727384,-0.0025374271571154713,
  -0.001438370315670195,-0.00035115295209013755,0.0002606730012030533,0.0001969569787142967,
  -0.00039635535951198597,-0.0010886127490608972,-0.0013530057243606405,-0.0008123200399262436,
  0.0005730271959526784,0.0024419465938120906,0.004133717273258681,0.0049402122577746265,
  0.0043879285604252714,0.002449549610687005,-0.00040283102645093463,-0.003337730734820209,
  -0.0054508346511294775,-0.006093057767824609,-0.005117609782189977,-0.0029293645861970417,
  -0.0003251033117661085,0.0018074390555649442,0.0028351284091668164,0.002623563404428517,
  0.0015692864792199496,0.0004127664681096788,-0.00009249878881824428,0.0004690173244168184,
  0.001964334172374759,0.0037256715492873485,0.004809640399145206,0.004395274594482053,
  0.0021650921193604,-0.0014888595443799124,-0.005534807968511709,-0.008642334104607624,
  -0.009668950651149259,-0.008104732391434574,-0.004299972815463919,0.0006184612821881392,
  0.005136551428636121,0.007907786753766152,0.008241212326068366,0.00634786595941524,
  0.003235610213062744,0.00028882736660937287,-0.001320994685952108,-0.0011237433853145615,
  0.00044213409507615003,0.0022057106517524255,0.00277593527678719,0.0011909915058737617,
  -0.0025807757230413447,-0.007497632882437637,-0.011739520895818884,-0.013377018279057393,
  -0.011166543231844196,-0.005133056165990026,0.0032948631959114935,0.011673660427968408,
  0.017376415708412904,0.018548938130314566,0.014811760899506572,0.007450782505155853,
  -0.001019540069785369,-0.007805775815783898,-0.010898333714715424,-0.00985364043415772,
  -0.005988406030111452,-0.001818560524968024,0.000028552677472614846,-0.0019938756495376363,
  -0.007477684025727061,-0.013989430449615033,-0.017870518868849213,-0.015639422062597726,
  -0.005624959109456065,0.010993528170353541,0.03001263681283932,0.04527492462846608,
  0.050581340787164114,0.041949186532860346,0.019360612460662185,-0.012644336735920483,
  -0.0458782599058412,-0.07073838953156347,-0.0791205623455818,-0.06709535677423759,
  -0.03644544574795176,0.005505370370858695,0.04780486657828151,0.07898800597378192,
  0.0904453420042807,0.07898800597378192,0.04780486657828151,0.005505370370858695,
  -0.03644544574795176,-0.06709535677423759,-0.0791205623455818,-0.07073838953156347,
  -0.0458782599058412,-0.012644336735920483,0.019360612460662185,0.041949186532860346,
  0.050581340787164114,0.04527492462846608,0.03001263681283932,0.010993528170353541,
  -0.005624959109456065,-0.015639422062597726,-0.017870518868849213,-0.013989430449615033,
  -0.007477684025727061,-0.0019938756495376363,0.000028552677472614846,-0.001818560524968024,
  -0.005988406030111452,-0.00985364043415772,-0.010898333714715424,-0.007805775815783898,
  -0.001019540069785369,0.007450782505155853,0.014811760899506572,0.018548938130314566,
  0.017376415708412904,0.011673660427968408,0.0032948631959114935,-0.005133056165990026,
  -0.011166543231844196,-0.013377018279057393,-0.011739520895818884,-0.007497632882437637,
  -0.0025807757230413447,0.0011909915058737617,0.00277593527678719,0.0022057106517524255,
  0.00044213409507615003,-0.0011237433853145615,-0.001320994685952108,0.00028882736660937287,
  0.003235610213062744,0.00634786595941524,0.008241212326068366,0.007907786753766152,
  0.005136551428636121,0.0006184612821881392,-0.004299972815463919,-0.008104732391434574,
  -0.009668950651149259,-0.008642334104607624,-0.005534807968511709,-0.0014888595443799124,
  0.0021650921193604,0.004395274594482053,0.004809640399145206,0.0037256715492873485,
  0.001964334172374759,0.0004690173244168184,-0.00009249878881824428,0.0004127664681096788,
  0.0015692864792199496,0.002623563404428517,0.0028351284091668164,0.0018074390555649442,
  -0.0003251033117661085,-0.0029293645861970417,-0.005117609782189977,-0.006093057767824609,
  -0.0054508346511294775,-0.003337730734820209,-0.00040283102645093463,0.002449549610687005,
  0.0043879285604252714,0.0049402122577746265,0.004133717273258681,0.0024419465938120906,
  0.0005730271959526784,-0.0008123200399262436,-0.0013530057243606405,-0.0010886127490608972,
  -0.00039635535951198597,0.0001969569787142967,0.0002606730012030533,-0.00035115295209013755,
  -0.001438370315670195,-0.0025374271571154713,-0.0031256650498727384,-0.0028402136847527387,
  -0.0016358832300944531,0.00017954815260431595,0.002060848732332109,0.003416201274366522,
  0.0038325849735515363,0.0032107930896349583,0.0018039564602637683,0.00010700092934983156,
  -0.001333859049002249,-0.002129903305507943,-0.002170446498273018,-0.00162618205097997,
  -0.0008521761947454302,-0.00024181463305012626,-0.00007527524701314324,-0.00039687498737139273,
  -0.0009759556503342884,-0.0014133823230551277,-0.0013703600874774068,-0.0007608257014963959,
  0.00025190669718400967,0.0014154004589753215,0.002461420635709332,0.003012423848769931,
  0.0026079871108133294,0.001115432556294998,-0.0008531818129514857,-0.0022783059845596586,
  -0.002770673157048994,-0.0029796565504781646,-0.003430943381749411,-0.0031973449396977684,
  -0.0008968429179843104,0.0024777666109278788,0.0033131082058404943,0.000032074683390218124,
  0.0033473431384214393
};

void ComputeFIR(double *coeffs, double *input,  int filterLength,ofstream &o )
{
    double acc;
    double *coeffp;
    int n,k,ip,nip;
    o<<fixed;
    for ( n = 0; n < 150000; n++ )
    {
        coeffp = coeffs;
        ip=(filterLength - 1 + n);
        nip=0;

        acc = 0;
        for ( k = 0; k < filterLength; k++ )
        {
            nip=ip-k;
            acc += ((*coeffp++) * (input[nip]));                  //      *inputp--  we can't use bcoz dynamic memory is not neccasarily in sequence);
        }
        o<<n<<","<<acc<<endl;
        if(n<10)
        {
            cout<<n<<"\t"<<acc<<endl;
        }
    }
}


int main()
{
    int i;

    ofstream o("400hz.csv");
    cout<<fixed;
    o<<fixed;
    double *buffer=new double[150264];                             //      Length required to process M input samples is N-1+M  where N is MAC , M is the Number of samples

   memset(buffer, 0, sizeof( buffer));

   for(i =(FILTER_LEN - 1); i < 150264; i++)
   {
            buffer[i] = sin(400 * (2 * pi) * (i / 5000.0));
            o<<i<<","<<buffer[i]<<endl;
    }

   ComputeFIR( coeffs,buffer,FILTER_LEN,o );

   delete []buffer;
   return 0;
}

在此代码部分

if(n<10)
            {
                cout<<n<<"\t"<<acc<<endl;
            }

在代码块中给出结果

0 0.002291

1 0.003205

2 0.005587

3 0.007458

4 0.006254

5 0.001537

6 -0.005113

7 -0.011685

8 -0.0016522

9 -0.018142

符合预期

在 Visual Studio 中的结果是

0 7.86052E+64

1 7.88065E+64

2 9.96043E+64

3 1.15158E+65

4 1.09528E+65

5 8.94574E+64

6 6.79198E+64

7 4.92152E+64

8 3.18225E+64

9 1.75206E+64

请帮助解决此问题。

4

2 回答 2

5

以下行不会将您的缓冲区初始化为零：

memset(buffer, 0, sizeof( buffer));

你需要

memset(buffer, 0, sizeof(double) * 150264);

也许 CodeBlocks 和 VS2012 在初始化缓冲区的方式上有所不同。

于 2013-04-26T06:31:51.937 回答
2

当使用不同的编译器时，相同的代码会产生不同的结果，这是未定义行为的明确标志。

这种未定义行为背后的原因是因为：

memset(buffer, 0, sizeof( buffer));

第一个问题是变量buffer是一个指针，所以使用sizeof(buffer)你得到实际指针的大小而不是它指向的大小。这意味着只有四个或八个字节（取决于您是否拥有 32 位或 64 位平台）将被初始化为零。其余的记忆似乎是随机的。

在这种情况下（但仅在这种情况下）有效的第二个问题是您将所有数据设置为零。浮点数不像普通整数那样存储在内存中。您不能memset与任何其他值一起使用并期望数字是您想要的。

于 2013-04-26T06:35:19.840 回答