Error in function call in C

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"SPADecoder" Function not returning any value. I have added Print statement inside the

"SPADecoder" Function

its not Printing any statements and values.

I am unable to find out the error in

"SPADecoder" Function

. Please point out me. Thanks

#include <stdio.h>
#include <math.h>

#define COL 204
#define COL_P 2
#define ROWS_P 1020

int codecheck(int (*h)[2],int x[])
{
    int i,j,m,f; //flags
	int sum = 0;
	int y[COL];
    for (i=0;i<COL;i++)
	y[i]=0;
	m=1;
	f=-1;
	for(i=0;i<ROWS_P;i++)
	{
		for(j=0;j<COL_P;j++)
		{
			if(h[j][0]==m)
			{
				y[m]=y[m] + x[h[j][1]-1];
					f++;
			}
		}
		y[m]=y[m]%2;
		m=m+1;
		i=f+1;
	}

	for (i = 0; i < COL; ++i)
		{
			sum =sum+ y[i];
		}
	if (sum == 0)
		{
			return 1;
		}
	else
		{
			return -1;
		}

}

int codesum (int y[])
{
    int sum=0;
    for(int i=0;i<COL;i++)
        sum+=y[i];
    //cout<< "sum="<< sum<<endl;
    if(sum>0)
        return 0;
    else
        return 1;
}

/*void ModulationSchemeValues (int modulationScheme, int noOfSymbols, double var, float d, float rate, double snr)
{
           switch (modulationScheme)
            {
                case 0:
                    //cout<<"case 0"<<endl;
                    var=1/(2*rate*snr);
                    noOfSymbols = COL;
                    d=1;
                    break;
                case 1:
                    //cout<<"case 1"<<endl;
                    var=1/(4*rate*snr);
                    noOfSymbols = COL/2;
                    d=1/sqrt(2);
                    break;
                case 2:
                    //cout<<"case 2"<<endl;
                    var=1/(8*rate*snr);
                    noOfSymbols = COL/4;
                    d=1/sqrt(10);
                default:
                    var=1/(2*rate*snr);
                    noOfSymbols = COL;
                    d=1;
                    break;
            }
    printf("%d %d %f %f %f %d",modulationScheme,noOfSymbols, var, d,rate, snr);
}

void InitializeChannelLLR (double var, int modulationScheme, int noOfSymbols, int x[], float noise[], double L_ch[], float d, int (*h)[2], double LLR[])
{

    int j=0;   // temporary flags
   int k=0,t;
    for(int i=0;i<noOfSymbols;i++)							// using randnoise function introducing noise to all zero codeword
    {

            x[j]=d;
            noise[j]=(x[j])+0.8;
            L_ch[j]= 2*noise[j]/var;
            j++;


    }


    for(int j=0;j<ROWS_P;j++)
    {
        //cout<<"enter loop"<<endl;
        //cout<< "j="<<j<<endl;  //<<j<<"\t";
        t=h[j][1]-1;
        LLR[j]=L_ch[t];
    }
    //cout<<"L_ch initialize done \n";

}*/

int SPADecoder(double LLR[], int (*h)[2], double LLR_ret[], double L_ch[],  double L_dec[], int y[])
{

    double temp;
    int z;
    int i,j,k;
    for(i=0;i<ROWS_P;i++)
    {
        temp=1;
        for(j=0;j<ROWS_P;j++)
        {
            if(j!=i && h[j][0]==h[i][0])
            {
                temp=temp * tanhf(LLR[j]/2);
            }
        }
        LLR_ret[i] = log((1 + temp)/(1 - temp));     // lower and upper bounding the LLR

        if(LLR_ret[i] > 40)
        {
            LLR_ret[i]=40;
        }
        else if(LLR_ret[i]<-40)
        {
            LLR_ret[i]=-40;
        }

    }

    for(i=0;i<COL;i++)							/
    {
        L_dec[i]=L_ch[i];
    }


    for(i=1;i<COL+1;i++)						
    {
        for(j=0;j<ROWS_P;j++)
        {
            if(h[j][1]==i)
            {
                L_dec[i-1]=L_dec[i-1]+LLR_ret[j];
            }

        }

        if(L_dec[i-1]<=0)						
        {
            y[i-1]=1;
        }
        else
        {
            y[i-1]=0;
        }

    }


    //z = codesum(y,col);
    z=codecheck(h,y); // checking whether the decoded codeword is all zero or not

    if(z==1)								// if decoded perfectly exit the deoding loop
    {
        return z;
    }
   
    for(i=0;i<ROWS_P;i++)
    {
        temp=0;
        for(j=0;j<ROWS_P;j++)
        {
            if(j!=i && h[j][1]==h[i][1])
            {
                temp=temp + LLR_ret[j];
                k=h[i][1];

            }
        }
        LLR[i] = temp+L_ch[k-1];
    }
return z;
}

int main()
{

	// flags and counters
    int z,i,j,N,k,ber_count,looping,t,sum;
    float d=1;
	float rate=0.5;

	int maxTransmissions=20,decoderIterations=10,maxErrors=50,errorsAccumulated=0;
	int y[COL];	/
    int L,O,R,M=0;

	double var=0,snr;
	double temp; 								//temp variable

    float noise[COL];
    double L_ch[COL],L_dec[COL];
	double LLR[ROWS_P],LLR_ret[ROWS_P];
	double BER[11];
    float snr_db[]={0,1,2,3,4};
    int snr_range=5,snr_count;
	int x[]={1,1,1,0,0,1,0,1,0,1,0,0,1,1,0,1,0,1,0,1,0,1,1,0,1,1,0,1,0,1,0,1,0,1,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,0,0,1,0,0,0,1,1,1,0,0,0,0,1,0,0,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,1,0,1,0,1,1,0,1,1,0,1,1,1,1,1,1,0,0,0,0,1,1,1,1,0,0,1,1,1,0,0,1,1,1,1,1,0,1,0,1,1,0,0,0,0,0,1,0,0,0,0,0,1,0,0,1,1,0,1,1,1};
    int  ret,row=0;
	double error_bits,error;
    int modulationScheme = 0,noOfSymbols=204;
    int h[ROWS_P][COL_P]={{1,1},{1,18},{1,27},{1,82},{1,102},{1,103},{1,130},{1,177},{1,190},{1,203},{2,2},{2,15},{2,75},{2,80},{2,86},{2,104},{2,121},{2,141},{2,144},{2,191},{3,3},{3,31},{3,32},{3,42},{3,101},{3,105},{3,153},{3,159},{3,178},{3,199},{4,4},{4,37},{4,71},{4,75},{4,85},{4,106},{4,111},{4,114},{4,127},{4,164},{5,5},{5,17},{5,42},{5,72},{5,87},{5,107},{5,141},{5,158},{5,193},{5,197},{6,4},{6,6},{6,17},{6,78},{6,102},{6,108},{6,162},{6,165},{6,167},{6,174},{7,7},{7,23},{7,73},{7,80},{7,83},{7,109},{7,118},{7,168},{7,177},{7,178},{8,8},{8,33},{8,37},{8,73},{8,100},{8,110},{8,156},{8,173},{8,192},{8,197},{9,9},{9,40},{9,41},{9,88},{9,92},{9,103},{9,111},{9,173},{9,181},{9,199},{10,10},{10,14},{10,23},{10,53},{10,93},{10,107},{10,112},{10,137},{10,167},{10,175},{11,11},{11,19},{11,26},{11,28},{11,88},{11,110},{11,113},{11,116},{11,170},{11,191},{12,1},{12,12},{12,25},{12,86},{12,97},{12,108},{12,114},{12,124},{12,161},{12,192},{13,4},{13,13},{13,33},{13,34},{13,50},{13,115},{13,137},{13,140},{13,146},{13,160},{14,14},{14,31},{14,40},{14,58},{14,95},{14,116},{14,121},{14,166},{14,174},{14,203},{15,15},{15,68},{15,70},{15,87},{15,101},{15,109},{15,113},{15,117},{15,165},{15,180},{16,4},{16,16},{16,59},{16,67},{16,92},{16,118},{16,125},{16,131},{16,138},{16,151},{17,15},{17,17},{17,44},{17,71},{17,73},{17,119},{17,161},{17,190},{17,194},{17,198},{18,18},{18,47},{18,62},{18,85},{18,93},{18,120},{18,122},{18,125},{18,146},{18,181},{19,19},{19,22},{19,23},{19,37},{19,57},{19,121},{19,126},{19,130},{19,131},{19,143},{20,1},{20,20},{20,50},{20,51},{20,99},{20,106},{20,122},{20,169},{20,179},{20,200},{21,21},{21,32},{21,62},{21,72},{21,98},{21,123},{21,126},{21,154},{21,168},{21,204},{22,22},{22,31},{22,44},{22,89},{22,98},{22,124},{22,141},{22,160},{22,169},{22,176},{23,23},{23,32},{23,61},{23,65},{23,99},{23,125},{23,132},{23,133},{23,147},{23,152},{24,16},{24,24},{24,42},{24,73},{24,77},{24,126},{24,142},{24,145},{24,146},{24,147},{25,5},{25,24},{25,25},{25,55},{25,67},{25,127},{25,133},{25,165},{25,178},{25,185},{26,10},{26,26},{26,27},{26,40},{26,85},{26,128},{26,147},{26,155},{26,160},{26,200},{27,22},{27,27},{27,42},{27,50},{27,74},{27,108},{27,129},{27,154},{27,170},{27,195},{28,2},{28,28},{28,63},{28,67},{28,94},{28,130},{28,150},{28,171},{28,187},{28,192},{29,29},{29,48},{29,69},{29,79},{29,90},{29,116},{29,131},{29,159},{29,176},{29,200},{30,7},{30,30},{30,53},{30,58},{30,94},{30,127},{30,132},{30,140},{30,162},{30,189},{31,29},{31,31},{31,64},{31,77},{31,94},{31,117},{31,133},{31,167},{31,183},{31,190},{32,20},{32,30},{32,32},{32,74},{32,78},{32,115},{32,134},{32,151},{32,181},{32,194},{33,11},{33,33},{33,47},{33,76},{33,81},{33,109},{33,135},{33,154},{33,155},{33,179},{34,2},{34,7},{34,34},{34,71},{34,76},{34,136},{34,138},{34,159},{34,182},{34,183},{35,27},{35,29},{35,35},{35,60},{35,86},{35,123},{35,137},{35,149},{35,166},{35,189},{36,17},{36,35},{36,36},{36,48},{36,100},{36,138},{36,139},{36,146},{36,163},{36,168},{37,5},{37,34},{37,37},{37,38},{37,69},{37,117},{37,139},{37,145},{37,169},{37,203},{38,38},{38,56},{38,76},{38,92},{38,101},{38,106},{38,123},{38,140},{38,161},{38,170},{39,39},{39,41},{39,60},{39,76},{39,78},{39,125},{39,141},{39,142},{39,175},{39,198},{40,2},{40,35},{40,40},{40,43},{40,93},{40,114},{40,135},{40,142},{40,148},{40,158},{41,1},{41,2},{41,13},{41,41},{41,59},{41,109},{41,119},{41,132},{41,143},{41,157},{42,11},{42,42},{42,43},{42,92},{42,95},{42,115},{42,117},{42,144},{42,156},{42,204},{43,7},{43,9},{43,43},{43,45},{43,56},{43,122},{43,145},{43,192},{43,194},{43,201},{44,10},{44,44},{44,75},{44,83},{44,95},{44,110},{44,135},{44,146},{44,157},{44,180},{45,45},{45,63},{45,79},{45,81},{45,97},{45,127},{45,139},{45,147},{45,148},{45,195},{46,34},{46,46},{46,61},{46,66},{46,77},{46,105},{46,144},{46,148},{46,197},{46,201},{47,14},{47,20},{47,46},{47,47},{47,83},{47,124},{47,128},{47,132},{47,149},{47,159},{48,8},{48,13},{48,26},{48,48},{48,62},{48,149},{48,150},{48,174},{48,193},{48,195},{49,15},{49,21},{49,25},{49,49},{49,51},{49,145},{49,149},{49,151},{49,177},{49,188},{50,8},{50,49},{50,50},{50,54},{50,89},{50,105},{50,126},{50,152},{50,164},{50,165},{51,43},{51,51},{51,66},{51,68},{51,91},{51,131},{51,133},{51,153},{51,187},{51,189},{52,1},{52,39},{52,45},{52,52},{52,54},{52,110},{52,140},{52,150},{52,154},{52,163},{53,8},{53,53},{53,60},{53,64},{53,90},{53,138},{53,155},{53,157},{53,194},{53,204},{54,12},{54,28},{54,54},{54,60},{54,82},{54,112},{54,139},{54,151},{54,156},{54,183},{55,3},{55,17},{55,37},{55,55},{55,99},{55,112},{55,148},{55,157},{55,172},{55,189},{56,20},{56,31},{56,56},{56,80},{56,91},{56,152},{56,156},{56,158},{56,162},{56,180},{57,28},{57,57},{57,66},{57,81},{57,89},{57,134},{57,137},{57,159},{57,172},{57,196},{58,5},{58,58},{58,70},{58,78},{58,91},{58,118},{58,149},{58,154},{58,160},{58,201},{59,18},{59,24},{59,59},{59,88},{59,96},{59,150},{59,152},{59,161},{59,179},{59,183},{60,21},{60,38},{60,55},{60,59},{60,60},{60,162},{60,176},{60,187},{60,190},{60,197},{61,61},{61,69},{61,74},{61,93},{61,101},{61,111},{61,128},{61,163},{61,193},{61,196},{62,6},{62,7},{62,35},{62,62},{62,96},{62,103},{62,113},{62,129},{62,164},{62,200},{63,16},{63,27},{63,44},{63,63},{63,88},{63,121},{63,134},{63,165},{63,175},{63,188},{64,4},{64,26},{64,64},{64,79},{64,84},{64,119},{64,134},{64,136},{64,166},{64,168},{65,12},{65,13},{65,52},{65,57},{65,65},{65,106},{65,138},{65,142},{65,167},{65,176},{66,24},{66,30},{66,52},{66,66},{66,102},{66,112},{66,117},{66,122},{66,135},{66,168},{67,6},{67,57},{67,67},{67,85},{67,97},{67,140},{67,169},{67,182},{67,184},{67,186},{68,6},{68,58},{68,68},{68,71},{68,90},{68,134},{68,143},{68,145},{68,152},{68,170},{69,54},{69,57},{69,59},{69,69},{69,77},{69,103},{69,104},{69,114},{69,136},{69,171},{70,19},{70,24},{70,56},{70,70},{70,100},{70,105},{70,114},{70,128},{70,129},{70,172},{71,14},{71,52},{71,63},{71,70},{71,71},{71,120},{71,169},{71,173},{71,178},{71,196},{72,11},{72,25},{72,39},{72,66},{72,72},{72,120},{72,130},{72,132},{72,174},{72,199},{73,48},{73,49},{73,64},{73,73},{73,98},{73,111},{73,175},{73,179},{73,201},{73,202},{74,9},{74,15},{74,58},{74,74},{74,84},{74,107},{74,120},{74,135},{74,164},{74,176},{75,28},{75,41},{75,70},{75,75},{75,96},{75,133},{75,155},{75,166},{75,177},{75,202},{76,26},{76,45},{76,65},{76,76},{76,94},{76,144},{76,158},{76,172},{76,178},{76,203},{77,10},{77,13},{77,77},{77,84},{77,87},{77,127},{77,151},{77,163},{77,179},{77,191},{78,49},{78,55},{78,65},{78,78},{78,90},{78,122},{78,130},{78,139},{78,180},{78,182},{79,33},{79,43},{79,67},{79,79},{79,99},{79,123},{79,141},{79,181},{79,188},{79,202},{80,18},{80,19},{80,35},{80,46},{80,80},{80,153},{80,167},{80,182},{80,188},{80,193},{81,9},{81,16},{81,36},{81,55},{81,81},{81,143},{81,160},{81,183},{81,186},{81,191},{82,10},{82,11},{82,79},{82,82},{82,96},{82,108},{82,111},{82,126},{82,172},{82,184},{83,12},{83,36},{83,69},{83,83},{83,87},{83,148},{83,174},{83,185},{83,202},{83,204},{84,45},{84,47},{84,48},{84,75},{84,84},{84,108},{84,123},{84,142},{84,153},{84,186},{85,9},{85,46},{85,53},{85,54},{85,85},{85,115},{85,121},{85,129},{85,177},{85,187},{86,22},{86,64},{86,83},{86,86},{86,91},{86,107},{86,116},{86,171},{86,188},{86,199},{87,8},{87,22},{87,61},{87,81},{87,87},{87,104},{87,120},{87,182},{87,189},{87,198},{88,32},{88,33},{88,39},{88,51},{88,88},{88,129},{88,143},{88,171},{88,180},{88,190},{89,3},{89,21},{89,52},{89,89},{89,100},{89,103},{89,109},{89,115},{89,125},{89,191},{90,20},{90,40},{90,44},{90,61},{90,90},{90,118},{90,137},{90,153},{90,184},{90,192},{91,6},{91,23},{91,29},{91,84},{91,91},{91,144},{91,155},{91,173},{91,185},{91,193},{92,14},{92,49},{92,72},{92,92},{92,102},{92,147},{92,171},{92,185},{92,186},{92,194},{93,5},{93,21},{93,29},{93,65},{93,93},{93,105},{93,110},{93,119},{93,184},{93,195},{94,39},{94,80},{94,82},{94,94},{94,98},{94,107},{94,113},{94,131},{94,166},{94,196},{95,30},{95,47},{95,50},{95,63},{95,95},{95,104},{95,118},{95,161},{95,163},{95,197},{96,25},{96,34},{96,56},{96,68},{96,96},{96,116},{96,181},{96,186},{96,196},{96,198},{97,36},{97,38},{97,46},{97,89},{97,97},{97,113},{97,136},{97,150},{97,157},{97,199},{98,3},{98,12},{98,18},{98,30},{98,98},{98,136},{98,170},{98,187},{98,198},{98,200},{99,53},{99,62},{99,74},{99,97},{99,99},{99,104},{99,119},{99,156},{99,185},{99,201},{100,16},{100,68},{100,82},{100,95},{100,100},{100,106},{100,124},{100,158},{100,195},{100,202},{101,19},{101,36},{101,41},{101,72},{101,101},{101,112},{101,124},{101,162},{101,164},{101,203},{102,3},{102,38},{102,51},{102,86},{102,102},{102,128},{102,173},{102,175},{102,184},{102,204}};


	printf("encoder \n");

	for (L = 0; L < 204; L++)
    {
      printf("%d",x[L]);
    }
    //printf(" \n Matrix \n");
/*for(M=0; M<ROWS_P; M++)
{
   loop for second dimension of array which is 4 in this example
     for(O=0;O<COL_P;O++)
     {
         printf("%d \t",h[M][O]);
     }
     printf("\n");
}*/

    for(snr_count=0;snr_count<snr_range;snr_count++)
	{
      //  cout<<"Decoder run for SNR in db=" <<snr_db[snr_count]<<endl;
				snr=pow(10,(snr_db[snr_count]/10));

                 printf(" \n ModulationSchemeValue \n");

                 printf(" \n%d %d %f %f %f %d\n",modulationScheme,noOfSymbols, var, d,rate, snr);
				//ModulationSchemeValues (modulationScheme, noOfSymbols, var, d, rate, snr);  // determining various values based on modulation scheme

                var=1/(2*rate*snr);
                noOfSymbols = COL;
                d=1;
                printf(" \n%d %d %f %f %f %d\n",modulationScheme,noOfSymbols, var, d,rate, snr);

                printf("\n");
        					// calulating noise variance from SNR
				BER[snr_count]=0;									// initializing BER
             //   normal_distribution<double> dist(0.0, 1);
                N=0;
                errorsAccumulated=0;

                printf(" \n InitializeChannelLLR\n");
				while(errorsAccumulated<=maxErrors && N<=maxTransmissions)
				{
                        N++;

                        for(int i=0;i<noOfSymbols;i++)							/
                           {

                                x[M]=d;
                                noise[M]=(x[M])+0.8;
                                L_ch[M]= 2*noise[M]/var;
                                M++;

                            }


                       for(int M=0;M<ROWS_P;M++)
                           {

                               R=h[M][1]-1;
                               LLR[M]=L_ch[R];

                          }
                               printf(" %d",LLR[M]);
                       

                           for(looping=0;looping<decoderIterations;looping++)
						   {

                              z = SPADecoder(LLR, h, LLR_ret, L_ch, L_dec, y);

						   }

                          if(z==1)											// if decoded correctly BER for that codeword is zero

                          {

                             BER[snr_count]=BER[snr_count]+0;

                          }
                         else 												// if not decoded properly calulating the BER
                          {
                            error_bits=0;
                            for(i=0;i<COL;i++)
									{
										if(y[i]!=0)
										{
											error_bits++;

										}
									}
                            errorsAccumulated+=error_bits;
                            error=error_bits/(double)COL;
                            BER[snr_count]=BER[snr_count]+error;
                          }
                       if(N%300==0)
                           printf("iteration=%d \t errors accumulated=%d \n",N,errorsAccumulated);
                }

                    BER[snr_count]=BER[snr_count]/(double)N; 					// averaging BER over all decoding iterations.
                    BER[snr_count]=BER[snr_count]/(double)N; 					// averaging BER over all decoding iterations.
					printf("snr=%lf\tBER[%d]=%lf \n",snr_db[snr_count],snr_count,BER[snr_count]);

    }

    return 0;
}

What I have tried:

I have tried lot of times,

"SPADecoder" Function

not returning any values.

Posted 4-Sep-17 2:12am

Member 13261175

Updated 4-Sep-17 2:26am

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CPallini · Answer 1 · 2017-09-04T02:25:00

Solution 1

The debugger is your friend.
If your print statements are not executed, then code execution never reaches them, that's obvious. The debugger is the most powerful tool able to find out why.

Posted 4-Sep-17 2:25am

CPallini

OriginalGriff · Answer 2 · 2017-09-04T02:26:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C#

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using teh debugger to find out why. Put a breakpoint on your line:

C++

for(looping=0;looping<decoderIterations;looping++)

and run your app. Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?

This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

Yes, I could probably tell you what "the problem" is - but it's not difficult to do this yourself, and you will learn something really worthwhile at the same time!