determinant of matrix in c N*N dimension return error at //answer[r][s]=input[p][q];

mybm1

float determinant(float **input,int order)
{

int j,p,q,t,i;
float pr;
float d;
float *c;
//c=memory_alloc_2D1(row,column);
float **answer;
answer=memory_alloc_2D1(order,order);
float **b;
b=memory_alloc_2D1(order,order);

for(j=1;j<=order;j++)
{
int r=1,s=1;
for(p=1;p<=order;p++)
{

       for(q=1;q<=order;q++)
       		 {
        		        if(p!=1&&q!=j)
          				{
			
	answer\[r\]\[s\]=input\[p\]\[q\]; // error as segmentation fault
            				s++;
            				if(s>order-1)
             				{
               					r++;
               					s=1;
              				}   
          				 }
        		 }
    }

 	for(t=1,pr=1;t<=(1+j);t++)
 		pr=(-1)\*pr;
 		c\[j\]=pr\*determinant(b,order-1);
 }
 		for(j=1,d=0.0;j<=order;j++)
 		{
  			 d=d+(input\[1\]\[j\]\*c\[j\]);
 		}

return(d);

}

main.c

float determinantmatrix;
determinantmatrix=determinant(covariance1,waveframesize);

//covariance1 is the input matrix

jeron1

I'll guess that you are attempting to access past the end of an array. code like this,

for(j=1;j<=order;j++)

would normally look like this.

for(j=0;j<order;j++)

as array access is zero based, from 0 to (size - 1)

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment "Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst

mybm1

it compile finely but while running segmentation fault occur and couldnt printf the output.

jeron1

That issue (indexing past the end of an array) isn't a syntactic issue and won't be flagged by the compiler, it is a logic issue and you will only see a problem at run time.

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment "Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst

mybm1

but i cant find out where the logic is getting wrong can u help me out.

jeron1

Do you understand what I said about array access?

"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment "Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst

David Crow

maibam debina wrote:

//covariance1 is the input matrix

But you've not shown how it's defined. If you have something like:

float covariance1[5][8];

And you are trying to access it in determinant() like:

for (int p = 1; p <= 5; p++)
covariance1[p][q]...

You can expect an access violation.

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David Crow

The for() loops are wrong.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

mybm1

even though i change it, its not working..

mybm1

I cant get u properly can u please ellaborate...