Fractions are just = to 0

This is a discussion on Fractions are just = to 0 within the C Programming forums, part of the General Programming Boards category; I have made a program to multiply matrixs together. However when I try to put a fraction as one of ...

  1. #1
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    May 2011
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    1

    Fractions are just = to 0

    I have made a program to multiply matrixs together. However when I try to put a fraction as one of the values of a matrix it equals to zero. Here is my program any help will be much appreciated.

    Code:
    #include <stdio.h>
    #include <math.h>
    
    int main()
    
    {
    
    #define k 3
    #define m 5
    #define n 4
    int i,j,l;
    
    float A[k][m] = { {2,-1/3,0,2/3,4},
    				  {1/2,3/2,4,-2,1},
    				  {0,3,-9/7,6/7,4/3},
    				 };
    
    float B[m][n] = { {6/5,0,-2,1/3},
    				  {5,7/2,3/4,-3/2},
    				  {0,-1,1,0},
    				  {9/2,3/7,-3,3},
    				  {4,-1/2,0,3/4},
    				 };
    
    float C[k][n] = { {0,0,0,0},
    				  {0,0,0,0},
    				  {0,0,0,0},
    				 };
    
    for(i = 0 ; i < k ; i++)
    	{
    		for(j = 0 ; j < n ; j++)
    			{
    				for(l = 0 ; l < m ; l++)
    					{
    						C[i][j] += A[i][l]*B[l][j];
    					}
    			}
    	}
    	
    printf("      A \n------------\n");
    	
    for(i = 0 ; i < k ; i++)
    	{
    		for(j = 0 ; j < m ; j++)
    			{
    				printf("%.0f  ", A[i][j]);
    			}
    		printf("\n");
    	}
    
    printf("\n");
    printf("      B \n------------\n");
    
    for(i = 0 ; i < k ; i++)
    	{
    		for(j = 0 ; j < m ; j++)
    			{
    				printf("%.0f   ", B[i][j]);
    			}
    		printf("\n");
    	}
    	
    printf("\n");
    printf("      C \n------------\n");
    
    for(i = 0 ; i < k ; i++)
    	{
    		for(j = 0 ; j < m ; j++)
    			{
    				printf("%f  ", C[i][j]);
    			}
    		printf("\n");
    	}
    
    printf("\n");	 	    
    
    }
    this is what comes out
    A
    ------------
    2 0 0 0 4
    0 1 4 -2 1
    0 3 -1 0 1

    B
    ------------
    1 0 -2 0 5
    5 3 0 -1 0
    0 -1 1 0 4

    C
    ------------
    18 0 -4 0 1
    1 -1 10 -7 19
    19 10 -1 -3 1

  2. #2
    Programming Wraith GReaper's Avatar
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    Your fractions turn out to be zero because you're dealing with integers and integer division. You have to use float literals or double literals for this to work.
    Devoted my life to programming...

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