Floating point exception( core dump

Question

Program: So I made a program that take two numbers, N and L. N is the size of a 2D array and L is a number from 3 - 16. The program builds the array and starts at the center and works its way out in a counter clockwise spiral. I is the value of the center and its as you go through the array( in the spiral ) the value will increase by one. It it is prime, that number will be assigned to that spot and if not it * will take its place instead.

Error: I'm getting a "Floating point exception " error, how would I solve this?

Code:

 void Array_Loop( int *Array, int n, int L ) ;

int Is_Prime( int Number ) ;

int main( int argc, char *argv[] ){

  int **Array ;
  int n, L ;

  n = atoi( argv[1] ) ;
  L = atoi( argv[2] ) ;

  Matrix_Build( &Array, n, n ) ;
  Array_Loop( Array, n, L ) ;


  return 0 ;

}

void Array_Loop( int *Array, int n, int L ){

  int i, j, k, h ;
  int lctn, move;

  lctn = n / 2 + 1 ;
  i = lctn ;
  j = lctn ;
  move = 1

  while( i != 0 && j != n ){

    for( j = lctn ; j < lctn + move ; j++ ){

         if( L % 2 == 2) Array[i][j] = -1 ;
         else Array[i][j] = Is_Prime( L ) ;
         L++ ;
    }

    move = move * -1 ;

    for( i = i ; i > lctn - move ; i-- ){

      if( L % 2 == 2) Array[i][j] = -1 ;
      else Array[i][j] = Is_Prime( L ) ;
      L++ ;
    }

    move-- ;

    for( j = j ; j > lctn - move ; j-- ){

      if( L % 2 == 2) Array[i][j] = -1 ;
      else Array[i][j] = Is_Prime( L ) ;
      L++ ;
    }

    move = move * -1 ;

    for( i = i ; i < lctn - move ; i-- ){

      if( L % 2 == 2) Array[i][j] = -1 ;
      else Array[i][j] = Is_Prime( L ) ;
      L++ ;
    }

    move++ ;

  }

}


int Is_Prime( int Number ){

  int i ;

  for( i = 0 ; i < Number / 2 ; i++ ){

    if( Number % i != 0 ) return -1 ;

  }

  return Number ;

}

Solution 1

You are getting Floating point exception because Number % i, when i is 0:

int Is_Prime( int Number ){

  int i ;

  for( i = 0 ; i < Number / 2 ; i++ ){

    if( Number % i != 0 ) return -1 ;

  }

  return Number ;

}

Just start the loop at i = 2. Since i = 1 in Number % i it always be equal to zero, since Number is a int.

Solution 2

Floating Point Exception happens because of an unexpected infinity or NaN. You can track that using gdb, which allows you to see what is going on inside your C program while it runs. For more details: https://www.cs.swarthmore.edu/~newhall/unixhelp/howto_gdb.php

In a nutshell, these commands might be useful...

gcc -g myprog.c

gdb a.out

gdb core a.out

ddd a.out