Floating Point Comparison C++ - Finding maximum

Question

When I do floating point comparison I am getting inf printed in the output screen. Can anyone please help?

unsigned long long temp;
long double tempDec=0.0,max=0.0;
unsigned long long maxInd=0,j=0;

for(unsigned long long i=1;i<100;i++)
{
    j=i-1;
    temp=0;
    while(j>0)
    {
        if(returnGCD(j,i)==1)
        {
            temp++;
        }
        j--;
    }


    tempDec = ((long double)i)/((long double)temp);

    if(tempDec>max)
    {
        max=tempDec;
        maxInd=i;
    }
}

cout << max << " # " << maxInd << endl;

When I tried out this snippet, I am getting the output as

inf # 1

I don't know whats wrong with it. Only for an equal comparison we can use fabs(), is there any other special way to find out the greater number in float?

Answer 1

Your first iteration of the loop, temp=0 , j=0 making tempDec to be infinite because of division by 0. if(tempDec>max) will be true first time and sets max to infinity. From there onwards, that if will always be false.

Fix the code so you don't divide by 0.