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drum123 10Sep2011 18:45
Help!!segmentation fault
 
hello all,
I am stuck and am unable to proceed anywhere on account of segmentation fault:( in the following code...can anyone temme what im doing wrong and how to rectify it.any help will be welcome :nice:

Code:
#include<stdio.h>
#include<math.h>
#include<stdlib.h>


//Signum function
int sig(float a)
{
if (a>=0)
return 1 ;
else return -1;
}
//Function to return absolute value
/*double abs (double a)
{
if (a>=0)
return a;
else return -1*a;
}
*/
void main()

{
    int *b,l=3000,k,i;
    double a[3000],**c;
 
    if (c==NULL)
            {
              printf("error...""no memory left");
              exit(0);
            }
   



for(k=0;k<3000;k++)
{ a[k]=-k+0.6*k*0.6*k-0.36*k*k*k;
}
b=&l;

        for ( k=0;k<15;k++)
       
            {
              c[k]=(double *)malloc(*b/15 * sizeof(double));
                     
       
          if (c[k]==NULL)
                {
                      printf("error...""no memory left");
                      exit(0);
                }

            }         



double **denoising(double *arr,int *arrsize)
    {   
    int count=0,window[300],z_mean=0,stdev=0,start,stop,num=100,k,j;
    int *z_crossings=NULL;   
    double  thresh,temp[300],emean=0,**templ=NULL;
    double *energyframe=NULL; 
       
       
    // a block of memory is allocated to the pointer templ which is used to keep track of each template and contain its values
    templ=(double**)malloc(15*sizeof(double));
       
     
    if (templ==NULL)
            {
              printf("error...""no memory left");
              exit(0);
            }
   
        for ( k=0;k<15;k++)
       
            {
              templ[k]=(double *)malloc(*arrsize/15 * sizeof(double));
                     
       
          if (templ[k]==NULL)
                {
                      printf("error...""no memory left");
                      exit(0);
                }

            }   
   
    /*Initialises a rectangular window of size 300//
    for (i=0;i<300;i++)
    {
      window[i]=1;
    }
    */   
      start=0;
      stop=300;
       
    z_crossings= (int *)malloc((*arrsize-stop+1)*sizeof(int));
       
      if (z_crossings==NULL)
            {
              printf("error...""no memory left");
              exit(0);
            }
   
        energyframe=(double *)malloc((*arrsize-stop+1)*sizeof(double));
       
    if (energyframe==NULL)
            {
              printf("error...""no memory left");
              exit(0);
            }






      while(stop < *arrsize)
    {   
      energyframe[count]=0;
          z_crossings[count]=0;     
   
   
      for (j=start;j<stop;j++)
        { 
       
          //temp[j]=arr[j]*window[j-start];
            temp[j-start]=arr[j];
          //Computes energy in each frame//
          energyframe[count]+=temp[j-start]*temp[j-start];
              //Coomputes zero crossingsin each frame//
              z_crossings[count]+= 1/2*(abs(sig(temp[j-start+1])-sig(temp[j-start])));       
        }   
       
      start++;
          stop++;
          count++; 
    }
   
for( j=0;j<count;j++)
 {
 emean +=energyframe[j]/count;
 //z_mean +=z_crossings[j]/count;//
 }
/*for( j=0;j<count;j++)
 {
  stdev+=((z_mean-z_crossings[j])^2)/count;
 }
*/

//The mean of the energy in each frame is set as the threshold
thresh=emean;
//The threshold for zero crossings is set//
//num=z_mean + 3*sqrt(stdev);

j=0;
count=0;

do
    {
        if ((energyframe[j]>=thresh) && (z_crossings[j]<=num))
            { start=j ;
                while((energyframe[j]>=thresh) && (z_crossings[j]<=num))
                {
                    j++;
                }
            stop=j-1;
            for (i=start;i<=stop;i++)
                {
                templ[count][i-start]=arr[i];//Records each signal frame(denoised) in a template//
                }
                        count++ ;
              }
        else j++;
       
    }while(j<*arrsize);

  free(z_crossings);
  free(energyframe);
  z_crossings=NULL;
  energyframe=NULL;

return templ;
free(templ);
}
c=denoising(a,b);
int j=0;
while(c!=NULL)
{ j=0;
  while(c[j]!=NULL)
  {
  printf("%f",*c[j]);
    j++;
  }

}
free(c);
}

marino.DV 12Sep2011 02:51
Re: Help!!segmentation fault
 
well i can offer you a hello :P

shabbir 12Sep2011 06:49
Re: Help!!segmentation fault
 
Quote:
Originally Posted by marino.DV (Post 86801)
well i can offer you a hello :P
Moved to C-C++ forum

poornaMoksha 13Sep2011 07:55
Re: Help!!segmentation fault
 
1)The very first problem is what my compiler tells me when I try to compile this program
Quote:
segfault.c:27: warning: ‘c’ is used uninitialized in this function
2)
Code: c
double a[3000],**c; 
    if (c==NULL)
    {
      printf("error...""no memory left");
      exit(0);
    }
What are the intentions here? Firstly you are not initializing 'c' and then directly checking it for NULL ???

3)
Quote:
c[k]=(double *)malloc(*b/15 * sizeof(double));
c[k] means *(c+k). Which is value at address held at memory location 'c+k', but does the memory location 'c+k' belong to any variable in our program?
This is a problem as we are trying to access the stack address which does not belong to any variable of our program.

I could not go through the entire program as its quite messy. Can you explain what are you trying to achieve through this program?

sura 28Oct2011 23:51
Re: Help!!segmentation fault
 
just allocate the memory for c before checking c==null


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