why i get infinity ? can it solved?

Question

i have code like this, i try to get number from henon formula

public class henon 
{
    public static void main(String[] args) 
    {         
        double a = 0.3;
        double b = 1.4;    
        double k[] = new double[1026];
        k[0] = 0.01;
        k[1] = 0.02;              

        for(int i = 0; i < 1024; i++)
        {                       
            k[i+2] = 1 - (a * Math.pow(k[i+1], 2) + b * k[i]);          
            System.out.println( "nilai ke" + i +" adalah " + k[i]);
        }
    }               
}

how i can get infinity valuew in 24, 25 ...how to solve it?

what exactly are you trying to achieve? your k[] has `0.01,0.02,0.98588....` ..? — Nikhar, Apr 24 '12 at 12:42

paxdiablo · Answer 1 · 2012-04-24T12:43:40.897

0

You're getting "infinite" values because your calculations are going beyond the range of a double data type.

If you need more range, you'll have to resort to something like a bignum library, such as BigDecimal.

edited Apr 24 '12 at 12:43

answered Apr 24 '12 at 12:38

paxdiablo

854,327
234
1,573
1,953

@Marko, you're right of course, I mistakenly thought this was C hence my reference to MPIR. Changed to BigDecimal since it's more relevant to Java. – paxdiablo Apr 24 '12 at 12:42
Your proposal wasn't all wrong because people do crave the C library for speed. BigDecimal is crap in that category, but it's much easier to start with. – Marko Topolnik Apr 24 '12 at 12:45
can you give me donwload link for GMP – user1209555 Apr 24 '12 at 12:49
MPIR is at http://www.mpir.org/ and GMP is at http://gmplib.org/ - I've always gotten a better response to problems and suggestions from MPIR (a fork of GMP) so that's my preference. – paxdiablo Apr 24 '12 at 13:38

Balaswamy Vaddeman · Accepted Answer · 2012-04-24T13:00:53.233

0

BigDecimal is better for your requirement.

double and float are not useful for accurate results as Joshua bloch said in Effective Java.

BigDecimal k[] = new BigDecimal[1026];
        k[0] = new BigDecimal(0.01);
        k[1] = new BigDecimal(0.02);  
        for (int i = 2; i < k.length; i++) {
            k[i]=new BigDecimal(0.0);
        }

if you want double value of Bigdecimal ,you can use doubleValue() method.

edited Apr 24 '12 at 13:00

answered Apr 24 '12 at 12:42

Balaswamy Vaddeman

8,360
3
30
40

bigdecimal is new for me ... i try to change double with bigdecimal, but i get error in this double a = 0.3; double b = 1.4; – user1209555 Apr 24 '12 at 12:57
u may explain with good example i didnt get it,u can see my edited answer – Balaswamy Vaddeman Apr 24 '12 at 13:01
im already succes to do this but 1 problem bigdecimal can't use to math.pow in my code there is pow process can you help me sir ? – user1209555 Apr 24 '12 at 14:31
Bigdecimal has got pow() method u can try it – Balaswamy Vaddeman Apr 25 '12 at 04:53

why i get infinity ? can it solved?

2 Answers2