dynamic array problem

[tommysmyth]

This code is a function inside my FIR filter class, not the full code.

void clock()
	{
		ifstream storedFreq("stored_f_sf.txt");
		storedFreq>>f1;
		storedFreq>>sf1;
		storedFreq.close();

		ofstream myfile("SignalFile_FIR.txt", ios::out);

                x=new int [sf1];
                y=new int [sf1];

		for(double i=0;i<=f1;i=i+(f1/sf1))
		{
	x[n]=sam.getNextSample();

	y[n]=(b[0]*x[n]) + (b[1]*x[n-1]) + (b[2]*x[n-2])  + (b[3]*x[n-3])  + (b[4]*x[n-4])  + (b[5]*x[n-5])  + (b[6]*x[n-6])  + (b[7]*x[n-7])  + (b[8]*x[n-8])  + (b[9]*x[n-9])  + (b[10]*x[n-10])  + (b[11]*x[n-11])  + (b[12]*x[n-12])  + (b[13]*x[n-13])  + (b[14]*x[n-14])  + (b[15]*x[n-15])  + (b[16]*x[n-16])  + (b[17]*x[n-17])  + (b[18]*x[n-18])  + (b[19]*x[n-19])  + (b[20]*x[n-20])  + (b[21]*x[n-21])  + (b[21]*x[n-21]) + (b[22]*x[n-22])  + (b[23]*x[n-23])  + (b[24]*x[n-24])  + (b[25]*x[n-25])  + (b[26]*x[n-26])  + (b[27]*x[n-27])  + (b[28]*x[n-28])  + (b[29]*x[n-29]) + (b[30]*x[n-30]);
	myfile<<n<<"     "<<y[n]<<"\n";;
	n++;
		}
		myfile.close();
		n=0;
	}

	void print()
	{
		cout<<"\nCutoff Freq in Hz = 1.000000e+004\n";
		cout<<"Transition Band in Hz = 5.000000e+003\nStop Band Attenuation in dBs = -6.000000e+001\nNumber of FIR coeffs = 31\n";
		cout<<"\nFilter coefficients.\nIndex Coeff.s\n"<<endl;
		for(int i=0;i<=30;i++)
		{
			cout<<i<<"     "<<b[i]<<endl;
		}
	}

private:
double b[30],stest;
double* x;
double* y;
static int n;
char* readfile;
int f1,sf1;
Sampledwave sam;
SineWave sine;
};

My program wont compile because when creating the new arrays or even just one of them the values in the first for loop become wrong i.e sf1=0 f1=1076101120

The original values in this case should be f1=15000 sf1=40000.

sf1 and f1 come from a file and there file changes value. The size of the arrays needed will overflow the stack so that is why I need dynamic arrays.

I tried use a vector but same error.

The program compiles if I set arrays x and y to an initial value i.e. in private declare int x[30],y[30] and remove the new ints. But these value are only to test it.


Can anybody fix this problem.

[kbw]

What is n? I can't see where it's declared.

[tommysmyth]

In the main program it is set to zero. FIR_filter is the class.

int FIR_filter::n=0;

Here I just show one function in the class and its private members.I can post all my code if needed.

Error got:
Unhandled exception at 0x01342c4d in ca1parts.exe: 0xC0000005: Access violation writing location 0x000000f0.


Looking at y in Autos it has this error:
y 0x00000000 double * CXX0030: Error: expression cannot be evaluated


Just note that if I remove the for loop the program compiles with no errors.


-

[Moooce]

isn't

for(double i=0;i<=f1;i=i+(f1/sf1))

an infinate loop?

[rapidcoder]

You have created a 30-element array:
double b[30]

And in the for loop you are accessing the 31st element of it:
b[30]


Here, too:

for(int i=0;i<=30;i++)
{
cout<<i<<" "<<b[i]<<endl;
}

Hint: You can make the code much shorter by using nested for loops.

BTW: Why C++ and not MATLAB? MATLAB would point you exactly to the line, where you have a bug.

[kbw]

How do you know if your indexing into arrays x and y are correct? I can't see where the guarantee is that n >= 30.

[tommysmyth]

reply to Mooce
f1=15000 and sf1=40000 so it will loop for 40000 times in this case.
But x=new int [f1]; and/or y=new int [f1]; sets these to sf1=0 f1=1076101120.
I dont know why.

reply to Mooce
I change array b to b[31].. b does have 31 coeffs.
The for loop is displaying the 31 coeefs.
I have to use c++ because it is an assignment for college.

reply to kbw
In the main program it is initialised to zero. FIR_filter is the class.
int FIR_filter::n=0;

[tommysmyth]

Ok here is my full code so ye can look at it

The file a_b_coeff.txt has the following coeffs stored in it

-4.008966e-004 7.644686e-004 8.084927e-004 -3.649528e-003 2.232512e-003 6.247866e-003 -1.188778e-002 3.022512e-016 2.333917e-002 -2.451241e-002 -1.819363e-002 6.613097e-002 -3.661643e-002 -1.075111e-001 2.907484e-001 6.250000e-001 2.907484e-001 -1.075111e-001 -3.661643e-002 6.613097e-002 -1.819363e-002 -2.451241e-002 2.333917e-002 3.022512e-016 -1.188778e-002 6.247866e-003 2.232512e-003 -3.649528e-003 8.084927e-004 7.644686e-004 -4.008966e-004

DSPfilter.h

#ifndef dspFILTER_H
#define dspFILTER_H
#include <iostream>
#include<math.h>
#include<fstream>
#include <string.h>



using namespace std;


class Signal
{
	friend class FIR_filter;
public:
	Signal(){};
	Signal(int f,int a)
		:frequency(f),amp(a){};	
	
	virtual void load_file()=0;
	
	
protected:
	int frequency;
	int amp;
};


class SineWave: public Signal
{
	friend class FIR_filter;
public:
	
	SineWave(int f=0,int a=0,int sf=0)
		:Signal(f,a),samplingFreq(sf){};

	
	
	void load_file()
	{
		ofstream storedFreq("stored_f_sf.txt", ios::out);
		f0=frequency;
		sf0=samplingFreq;
		Pi=3.14159265;
		storedFreq<<f0<<" "<<sf0;
		storedFreq.close();

		ofstream SineWrite("SaveFile.txt", ios::out);
		for(double i=0;i<=f0;i=i+(f0/sf0))
		{
			
			SineWrite<<amp*sin(2*Pi*f0*t)<<" ";
			t=t+(1/sf0);
			count++;		
		}
		SineWrite.close();
		
	}

	int get_samplingFreq(){return samplingFreq;}
	

protected:
int samplingFreq;
double f0,sf0;
static int count;
static double t;
double x;
double Pi;
};

class Sampledwave:public SineWave
{
		friend class FIR_filter;
public:
	
	Sampledwave()
	{
	
	ifstream myfile("SaveFile.txt");
	if (!myfile.fail())
		{
		for (int i = 0;(!myfile.eof()); i++)
			{
				myfile >> sr[i];
			}
		myfile.close();
		
		}
	else
	{
		cout<<"Read SaveFile.txt Fail";
	}

	}

	
	int getNextSample(){return sr[sample1++];}
	
private:
	char* readfile;
	double sample;
	double sr[40000];
	int value;
	static int sample1;
	
};


class Filter
{
public:
	virtual void clock()=0;
	virtual	void get_Type()=0;
	virtual void print()=0;
protected:
};


class FIR_filter: public Filter
{
public:		
	FIR_filter(){
	
	ifstream myfile("a_b_coeff.txt");
	if (!myfile.fail())
		{
		for (int i = 0;(!myfile.eof()); i++)
			{
				myfile>>b[i];
			}
		myfile.close();
			
		}
	else
		{
		cout<<"Read a_b_coeff.txt Fail";
		}

	}

	void get_Type(){cout<<"Low Pass\n";}

	void clock()
	{
		ifstream storedFreq("stored_f_sf.txt");
		storedFreq>>f1;
		storedFreq>>sf1;
		storedFreq.close();

		ofstream myfile("SignalFile_FIR.txt", ios::out);
		x=new int[sf1];
		y=new int[sf1];
		for(double i=0;i<=f1;i=i+(f1/sf1))
		{
	x[n]=sam.getNextSample();
	y[n]=(b[0]*x[n]) + (b[1]*x[n-1]) + (b[2]*x[n-2])  + (b[3]*x[n-3])  + (b[4]*x[n-4])  + (b[5]*x[n-5])  + (b[6]*x[n-6])  + (b[7]*x[n-7])  + (b[8]*x[n-8])  + (b[9]*x[n-9])  + (b[10]*x[n-10])  + (b[11]*x[n-11])  + (b[12]*x[n-12])  + (b[13]*x[n-13])  + (b[14]*x[n-14])  + (b[15]*x[n-15])  + (b[16]*x[n-16])  + (b[17]*x[n-17])  + (b[18]*x[n-18])  + (b[19]*x[n-19])  + (b[20]*x[n-20])  + (b[21]*x[n-21])  + (b[21]*x[n-21]) + (b[22]*x[n-22])  + (b[23]*x[n-23])  + (b[24]*x[n-24])  + (b[25]*x[n-25])  + (b[26]*x[n-26])  + (b[27]*x[n-27])  + (b[28]*x[n-28])  + (b[29]*x[n-29]) + (b[30]*x[n-30]);
	myfile<<n<<"     "<<y[n]<<"\n";
	n++;
		}
		myfile.close();
		n=0;
	}

	void print()
	{
		cout<<"\nCutoff Freq in Hz = 1.000000e+004\n";
		cout<<"Transition Band in Hz = 5.000000e+003\nStop Band Attenuation in dBs = -6.000000e+001\nNumber of FIR coeffs = 31\n";
		cout<<"\nFilter coefficients.\nIndex Coeff.s\n"<<endl;
		for(int i=0;i<=30;i++)
		{
			cout<<i<<"     "<<b[i]<<endl;
		}
	}

private:
double b[31];
int* x;
int* y;
static int n;
char* readfile;
int f1,sf1;
Sampledwave sam;

};
#endif 

main.cpp

#include <iostream>
#include<math.h>
#include "DSPfilter.h"
#include<fstream>
#include <string.h>

int SineWave::count=0;
int FIR_filter::n=0;
double SineWave::t=0;
int Sampledwave::sample1=0;


using std::cout;
using namespace std;
using std::endl;

int main()
{	cout<<"Loading .....\n\n";
	SineWave s1(15000,10,40000);
	s1.load_file();
	Sampledwave sw1;
	FIR_filter fir1;
	cout<<"FIR\nType =";
	fir1.get_Type();
	cout<<"Sampling Freq in Hz ="<<s1.get_samplingFreq();
	fir1.print();
	fir1.clock();

	return 0;

}

[Incubbus]

please use code tags for this long code... place around it, or mark all the code and pick the '#' on the right side ("Format").

[kbw]

Your indexes are out of bounds, can't you see it?

What is x[n-29] when n is zero?

[tommysmyth]

Reply to Incubbus
Sorry this is my first topic on this site. Fixed now.

Reply to kbw
I assumed it would be zero.
Could initialize x[n-1] to x[n-30] to zero or is that possible? i.e. for loop

Or do something like this:

if(n=0)
{
y[n]=(b[0]*x[n]) ;
}

else if(n=1)
{
y[n]=(b[0]*x[n]) + (b[1]*x[n-1]) ;
}
.
.
.
.

else if(n=10)
{
y[n]=(b[0]*x[n]) + (b[1]*x[n-1]) + (b[2]*x[n-2]) + (b[3]*x[n-3]) + (b[4]*x[n-4]) + (b[5]*x[n-5]) + (b[6]*x[n-6]) + (b[7]*x[n-7]) + (b[8]*x[n-8]) + (b[9]*x[n-9]) + (b[10]*x[n-10]) ;
}
.

.
.
.
else if(n>=30)
{
y[n]=(b[0]*x[n]) + (b[1]*x[n-1]) + (b[2]*x[n-2]) + (b[3]*x[n-3]) + (b[4]*x[n-4]) + (b[5]*x[n-5]) + (b[6]*x[n-6]) + (b[7]*x[n-7]) + (b[8]*x[n-8]) + (b[9]*x[n-9]) + (b[10]*x[n-10]) + (b[11]*x[n-11]) + (b[12]*x[n-12]) + (b[13]*x[n-13]) + (b[14]*x[n-14]) + (b[15]*x[n-15]) + (b[16]*x[n-16]) + (b[17]*x[n-17]) + (b[18]*x[n-18]) + (b[19]*x[n-19]) + (b[20]*x[n-20]) + (b[21]*x[n-21]) + (b[21]*x[n-21]) + (b[22]*x[n-22]) + (b[23]*x[n-23]) + (b[24]*x[n-24]) + (b[25]*x[n-25]) + (b[26]*x[n-26]) + (b[27]*x[n-27]) + (b[28]*x[n-28]) + (b[29]*x[n-29]) + (b[30]*x[n-30]);
}

Or instread of if statements use cases?

[tommysmyth]

Solved

moooce was correct in saying

isn't
for(double i=0;i<=f1;i=i+(f1/sf1))
an infinate loop?

I declare sf1 and f1 as int's so (f1/sf1)=0 i.e (15000/40000)=0
I just changed them to double's

I used the if else statements above to solve the x[n-1] to x[n-30] when n<=30 problem

And then just one more problem needed to be changed.

int int_sf1;
int_sf1=sf1;

x=new int[int_sf1]; //array cannot be a double value
y=new int[int_sf1];