Name: gm110360 Date: 02/07/2003


FULL PRODUCT VERSION :
java version "1.4.0"
Java(TM) 2 Runtime Environment, STandard Edition (build 1.4.0-b92)
Java Hotspot(TM) Client VM (build 1.4.0-b92, mixed mode)

FULL OPERATING SYSTEM VERSION :
Microsoft Windows2000 [versie 5.00.2195]
Service Pack 3

A DESCRIPTION OF THE PROBLEM :
The method java.math.BigInteger.isProbablePrime(int) does
not recognize some Mersenne primes, e.g. 2^521-1

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1.Run the main in MersennePrint class below
2.
3.

EXPECTED VERSUS ACTUAL BEHAVIOR :
It prints the following:
2
3
5
7
13
17
19
31
61
89
107
127
607

So it is missing 521.


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.math.BigInteger;
public class MersennePrint {
    
    public MersennePrint() {
    }

    public static void main(String[] args) {
        // try to get the Mersenne primes
        for (int i = 2; i < 610; i++) {
            BigInteger bi =
                BigInteger.ONE.shiftLeft(i).subtract(BigInteger.ONE);
            if (bi.isProbablePrime(10)) {
                System.out.println(i);
            }
        }
    }
}

---------- END SOURCE ----------
(Review ID: 180967)
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