JDK 8 code review request for 7091682 "Move sun.misc.FpUtils code into java.lang.Math"

[Jeff Hain]

Hi.


There are some possible optimizations for some methods.


For nextAfter(double,double) (same for float version), instead of testing NaN-ity right away,
we can test most common (or at least regular) cases first:

public static double nextAfter(double start, double direction) {
    // Balancing out by branching to going-down case first,
    // for it is heavier than going-up case (test if start is +-0.0).
    if (start > direction) {
        // Going down.
        if (start == 0.0d) {
            // start is +0.0 or -0.0
            return -Double.MIN_VALUE;
        }
        final long transducer = Double.doubleToRawLongBits(start);
        assert transducer != 0L;
        return Double.longBitsToDouble(transducer + ((transducer > 0L) ? -1L:1L));
    } else if (start < direction) {
        // Going up.
        // Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0)
        // then bitwise convert start to integer.
        final long transducer = Double.doubleToRawLongBits(start + 0.0d);
        return Double.longBitsToDouble(transducer + ((transducer >= 0L) ? 1L:-1L));
    } else if (start == direction) {
        return direction;
    } else { // start and/or direction is NaN
        return start + direction;
    }
}

Same for nextUp(double) and float version (also, testing transducer >= 0L
instead of d >= 0.0D seems to help):
public static double nextUp(double d) {
    if (d < Double.POSITIVE_INFINITY) {
        final long transducer = Double.doubleToRawLongBits(d + 0.0D);
        return Double.longBitsToDouble(transducer + ((transducer >= 0L) ? 1L:-1L));
    } else { // d is NaN or +Infinity
        return d;
    }
}

-Jeff



________________________________
De : "joe.darcy at oracle.com" <joe.darcy at oracle.com>
À : core-libs-dev <core-libs-dev at openjdk.java.net>
Envoyé le : Samedi 17 Septembre 2011 3h52
Objet : JDK 8 code review request for 7091682 "Move sun.misc.FpUtils code into java.lang.Math"

Hello.

Please review the changes to address

   7091682 "Move sun.misc.FpUtils code into java.lang.Math"
  http://cr.openjdk.java.net/~darcy/7091682.0/

As implied by the synopsis, where appropriate JDK-implementation code used to provide functionality in java.lang.Math and java.lang.StrictMath is moved out of sun.misc.* and into java.lang.Math.  Uses of methods available in java.lang.Math and switched to that entry point as opposed to the sun.misc one.  Additionally, the sun.misc methods whose implementation was moved were also deprecated.

Later in JDK 8, I will probably add some of the remaining un-deprecated methods in sun.misc.FpUtils as java.lang.Math/StrictMath methods.

Thanks,

-Joe