Question

I am facing problem using float

in loop its value stuck at 8388608.00

int count=0;
    long X=10;
    cout.precision(flt::digits10);
    cout<<"Iterration #"<<setw(15)<<"Add"<<setw(21)<<"Mult"<<endl;
    float Start=0.0;
    float Multiplication = Addition * N;
    long i = 1;
    for (i; i <= N; i++){
        float temp = Start + Addition;
        Start=temp;
        count++;
        if(count%X==0 && count!=0)
        {
            X*=10;
            cout<<i;
            cout<<fixed<<setw(30)<<Start<<setw(20)<<fixed<<i*Addition<<endl;
        }
    }

what should i do??

Answer 1

Floating point addition doesn’t work when you’re adding (relatively) small number to (relatively) big one. It’s caused by the way float is stored in memory.

You may try replacing single precision floating point (float) with double precision floating point (double) representation but if that doesn’t work you’ll probably need to implement hack like this:

// Lets say
double OriginalAddition = 0.123;
int Addition = 1;

// You just use base math substitution:
// Addition = OriginalAddition
int temp = Start + Addition;  // You will treat transform floating point to fixed point
                              // with step 0.123, so 1 = 0.123
// And when displaying result (transform back into original floating point):
printf( "%f", (double)result*OriginalAddition)

This needs a lot of thought to find a substitution that doesn’t cause data loss, covers required precision and won’t cause int to overflow. Try to google fixed point int C (some results: 1, 2) to get better idea what to do.