In method java.math.Mutable.binaryGCD(MutableBigInteger) there is an assignment to a local object called q, but it is never used in the method.

    private MutableBigInteger binaryGCD(MutableBigInteger v) {
        // Algorithm B from Knuth section 4.5.2
        MutableBigInteger u = this;
        MutableBigInteger q = new MutableBigInteger(), // <----- here
            r = new MutableBigInteger();
        // step B1
        int s1 = u.getLowestSetBit();
        int s2 = v.getLowestSetBit();
        int k = (s1 < s2) ? s1 : s2;
        if (k != 0) {
            u.rightShift(k);
            v.rightShift(k);
        }

        // step B2
        boolean uOdd = (k==s1);
        MutableBigInteger t = uOdd ? v: u;
        int tsign = uOdd ? -1 : 1;

        int lb;
        while ((lb = t.getLowestSetBit()) >= 0) {
            // steps B3 and B4
            t.rightShift(lb);
            // step B5
            if (tsign > 0)
                u = t;
            else
                v = t;

            // Special case one word numbers
            if (u.intLen < 2 && v.intLen < 2) {
                int x = u.value[u.offset];
                int y = v.value[v.offset];
                x = binaryGcd(x, y);
                r.value[0] = x;
                r.intLen = 1;
                r.offset = 0;
                if (k > 0)
                    r.leftShift(k);
                return r;
            }
      
            // step B6
            if ((tsign = u.difference(v)) == 0)
                break;
            t = (tsign >= 0) ? u : v;
        }

        if (k > 0)
            u.leftShift(k);
        return u;
    }

The binaryGCD method is launched by the hybridGCD method, the hybridGCD method is launched by the BigInteger's public gcd method. By removing q in the snippet above, we can save both memory (the object itself) and execution time (the constructor), so the public BigInteger gcd(BigInteger val) can benefit from a fix.

###@###.### 2005-1-31 10:13:08 GMT