Printf outputting a bunch of zeros

Question

I'm new to C, so I apologize if the answer to this is painfully obvious! I mean to loop through two 2D arrays, passing correspondingly indexed members as arguments to my chineseRemainder routine, ie for each iteration, array1[i] and array2[i] should be passed to the routine, where i = i. I am expecting the output of a call to printf to be a certain set of numbers -- instead I am getting all zeros. Here is the main routine, where I call the CR function. **edit I gave xp and xq arbitrary int values, since they do not seem to be the problem, and giving them such values gives the same output.

int main(){

int xp, xq, p = 61, q = 3;
int i, j;

reverseInteger();

for(i = 0; i < 32; ++i){
    for(j = 0; j < 10; ++j){
        xq = 4;
        xp = 1;
        printf("%i\n", chineseRemainder(xq, xp, p, q));
            }
        }


return 0;

}

For troubleshooting's sake, I dumped the contents of xq and xp to make sure those assignments were going through: they are. The problem must be with the CR routine, because it is printing zero even when I pass any set of integers to it. So, here is that function, and its dependencies:

float power(int base, int exp) {

int i;
float result = 1;

if (exp == 0)
    result = 1;

else if (exp == 1)
    result = base;

else if(exp > 1){
    for (i = 0; i < exp; ++i)
        result *= base;
}

else
    result = 1/power(base, -exp);

return result;

}

float powerMod(int q, int e, int p){

float result;

result = (int)power(q, e) % p;

return result;

}

typedef struct arrayInside{

        int array[30][10];

    } arrayInside;              

arrayInside codesInside;            

struct arrayInside reverseInteger(){

int i, j, number;

for(i = 0; i < 30; ++i){
    j = 10;
    number = (aryConversion(q3[i], 3));
    do {
        codesInside.array[i][j-1] = number % 10;
        --j;
        number = number / 10;
    }
    while (number);
    codesInside.array[i][0] = 0;

};

return codesInside;
}

int chineseRemainder(int xq, int xp, int p, int q){

int tp;
int ceiling = (p*q-1)/2;

tp = ((int)(q * (powerMod(q, -1, p))*xp + p * powerMod(p, -1, q) * xq) % (p*q));
    if(tp > ceiling)
            tp-=p*q;

return tp;

}

Answer 1

Your chineseRemainder actually returns 0 every time. Look at this -

((int)(q * (powerMod(q, -1, p))*xp + p * powerMod(p, -1, q) * xq) % (p*q));

powerMod(q, -1, p) is zero. So multiplying and adding it also going to give zero. Your function actually returns zero. There is nothing wrong. You probably need to check the logic or change the data types.