我正在执行一个过滤器代码。这个代码在Visual Studio和代码块中给出了不同的结果。预期的结果是代码块给出的结果。但是，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 。请帮助找出原因存在差异的原因。
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;
}
将代码块中的结果显示为
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
这是预期的
并且在Visual Studio结果中
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。
答案 0 :(得分：5)
以下行不会将缓冲区初始化为零：
memset(buffer, 0, sizeof( buffer));
你需要
memset(buffer, 0, sizeof(double) * 150264);
也许CodeBlocks和VS2012在初始化缓冲区方面有所不同。
答案 1 :(得分：2)
使用不同的编译器时，使用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，因此使用sizeof(buffer)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（取决于您是否具有32位或64位平台）将初始化为零。其余的记忆似乎是随机的。
第二个问题，在这种情况下有效（但仅在这种情况下），是您将所有数据设置为零。浮点数不像存储器中的普通整数一样存储。您不能将memset与任何其他值一起使用，并期望这些数字符合您的要求。