0

```
Unhandled exception at 0x561330d9 (msvcr100d.dll) in main.exe: 0xC0000005: Access violation reading location 0x440b4bd8.
```

i try my best to debug it, but don't have clue on it.

**fft.h**

```
#include <math.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#define NR_END 1
#define FREE_ARG char*
#define M_PI 3.14159265358979323846264338327
static double sqrarg;
#define SQR(a) ((sqrarg=(a)) == 0.0 ? 0.0 : sqrarg * sqrarg)
#define WINDOW(j,a,b) (1.0 - fabs((((j)-1)-(a))*(b))) //Bartlett
void nrerror(char error_text [])
/* Numerical Recipes standard error handle*/
{
fprintf(stderr, "Numerical Recipes run time-time error...\n");
fprintf(stderr, "%s\n", error_text);
fprintf(stderr, "...now exiting to system...\n");
exit(1);
}
#define SWAP(a,b) tempr=(a);(a)=(b);(b)=tempr
void four1(double data[], unsigned long nn, int isign)
{
unsigned long n,mmax,m,j,istep,i;
double wtemp, wr,wpr,wpi,wi,theta;
double tempr, tempi;
n=nn<<1;
j=1;
for(i=1;i<n;i+=2)
{
if(j > i){
SWAP(data[j],data[i]);
SWAP(data[j+1],data[i+1]);
}
m=n >> 1;
while (m >= 2 && j >m)
{
j -=m;
m>>=1;
}
j +=m;
}
mmax=2;
while (n > mmax)
{
istep = mmax << 1;
theta = isign*(6.28318530717959/mmax);
wtemp=sin(0.5*theta);
wpr = -2.0*wtemp*wtemp;
wpi = sin (theta);
wr=1.0;
wi=0.0;
for(m=1;m<mmax;m+=2)
{
for(i=m;i<=n;i+=istep)
{
j=i+mmax;
tempr=wr*data[j]-wi*data[j+1];
tempi=wr*data[j+1]+wi*data[j];
data[j]=data[i]-tempr;
data[j+i]=data[i+1]-tempi;
data[i]+=tempr;
data[i+1] +=tempi;
}
wr=(wtemp=wr)*wpr-wi*wpi+wr;
wi=wi*wpr+wtemp*wpi+wi;
}
mmax = istep;
}
}
void realft(double data[], unsigned long n, int isign)
{
void four1(double data[], unsigned long n, int isign);
unsigned long i,i1,i2,i3,i4,np3;
double c1=0.5,c2,h1r,h1i,h2r,h2i;
double wr,wi,wpr,wpi,wtemp,theta;
theta=3.141592653589793/(double) (n>>1);
if(isign ==1)
{
c2 = -0.5;
four1(data,n>>1,1);
}
else
{
c2=0.5;
theta=-theta;
}
wtemp = sin(0.5*theta);
wpr = -2.0*wtemp*wtemp;
wpi=sin(theta);
wr=1.0+wpr;
wi=wpi;
np3=n+3;
for(i=2;i<=(n>>2);i++)
{
i4=1+(i3=np3-(i2=1+(i1=i+i-1)));
h1r=c1*(data[i1]+data[i3]);
h1i=c1*(data[i2]-data[i4]);
h2r= -c2*(data[i2]+data[i4]);
h2i=c2*(data[i1]-data[i3]);
data[i1]=h1r+wr*h2r-wi*h2i;
data[i2]=h1i+wr*h2i+wi*h2r;
data[i3]=h1r-wr*h2r+wi*h2i;
data[i4]= -h1i+wr*h2i+wi*h2r;
wr=(wtemp=wr)*wpr-wi*wpi+wr;
wi=wi*wpr+wtemp*wpi+wi;
}
if(isign == 1)
{
data[1]=(h1r=data[1])+data[2];
data[2] = h1r-data[2];
}
else{
data[1]=c1*((h1r=data[1])+data[2]);
data[2]=c1*(h1r-data[2]);
four1(data,n>>1,-1);
}
}
```

**Possible cause**

"n" = 8192, "i" it stop iterate somewhere around 4000+

```
while (n > mmax)
{
istep = mmax << 1;
theta = isign*(6.28318530717959/mmax);
wtemp=sin(0.5*theta);
wpr = -2.0*wtemp*wtemp;
wpi = sin (theta);
wr=1.0;
wi=0.0;
for(m=1;m<mmax;m+=2)
{
for(i=m;i<=n;i+=istep)
{
j=i+mmax;
tempr=wr*data[j]-wi*data[j+1];
tempi=wr*data[j+1]+wi*data[j];
data[j]=data[i]-tempr;
data[j+i]=data[i+1]-tempi;
data[i]+=tempr;
data[i+1] +=tempi;
}
wr=(wtemp=wr)*wpr-wi*wpi+wr;
wi=wi*wpr+wtemp*wpi+wi;
}
mmax = istep;
}
```

*Edited 3 Years Ago by overloaded*: more clarify